Friday, November 30, 2007





Example: Your ship's 0700 DR position on 24 January, 1981 is LAT 22° 25.0'N, LONG 46°
10.0'W. Your vessel is course 110T at a speed of 12.0 knots. What is the ZT of local apparent noon (LAN) ?

Step 1 Enter the appropriate date.

Step 2 Go to ''The Nautical Almanac" and extract the time of meridian passage for 24 January April 1981.

Step 3 Set up universal plotting sheet,Plot 0700 DR position and DR ahead to 1212 Example: 1212 - 0700 = 5h 12m at 12 knot = 62.4 miles

Step 4 Enter your DR longitude for the time of meridian passage you extracted from the almanac (1212).

Step 5 Enter the nearest standard meridian.

Step 6 Calculate the difference in arc between the standard meridian and your DR longitude.

Step 7 Convert the arc in step 5 into time using the "Conversion of Arc to Time" form the Nautical Almanac.

Step 8 Now apply the time correction to the time of meridian passage from the almanac. Because we are west of our standard meridian, we must add the difference by applying this correction you will have the time of LAN at the meridian for your DR position. This is called the first estimate of LAN:

Note: if you clocks are set to daylight savings time (DST); add one hour to your zone time or use the standard meridian that your clocks are set to.

To compute the time of LAN, I use a step by step process using this work from. After you do few problems you won't need this.


Direct Attack without Entry. Open the door slightly and direct a solid stream of water at the seat of the class A fire. Keep in mind that a solid stream of water can be projected approximately 75 feet when 100 psi is available at the fire main. This method of extinguishment may be desirable when the compartment has become superheated and entry by the fire fighters would result in too much body punishment to the fire fighters.
Indirect Attack (for Smaller Compartments). Fire extinguishment can be effected by briefly opening the door to the compartment that is on fire and then directing high-velocity fog into the overhead of the compartment. The superheated gases in the overhead will flash this water to steam and the steam will begin to fill the compartment. When sufficient steam has been generated in the compartment, close the door tightly and allow the steam to smother the fire. This method is useful for small compartments where the fire has progressed to the second or the third stage and the gases in the overhead have become superheated.
Direct Attack Using Proper Technique. Fire fighters enter the compartment and stay low to the deck. The 4-foot applicator is used for heat shielding and personnel cooling. As little water as possible is used from the attack nozzle so as not to stir up the thermal boundary in the overhead. The source of the fire is approached as closely as possible without using water. Solid stream is used directly on the seat of the class A fire.
Direct Attack Using Improper Technique. The result of this is that the water reaching the superheated gases in the overhead flashes to steam. The turbulence of the high velocity fog causes the thermal boundary to become disturbed. The superheated gases and steam are forced down to the deck from the overhead with the result that the fire fighter will be forced out of the compartment by overheating.


Once you arrive on scene to fight the fire you should cool down the door entrance to the compartment or zone on fire. Once the entrance is cool, a backup man can step forward and, while standing out­side the swing of the door, crack open the door and slip the 4-foot applicator into the opened door to continue cooling the back side of the door, It is im­portant to stand outside the swing of the door due to the possibility of the door being blown open when fresh air enters into the compartment through the crack in the door.
Open the door fully while using a vertical sweeping motion with the at­tack nozzle on high velocity fog. This water action will keep the smoke and fire gases inside the compartment.
At this point the emergency squad officer can make a determination as to what type of attack should be made. If the compartment is small then an indirect attack can be mounted from the compartment entrance. Types of indirect attack are as follows:
1. Point attack nozzle into overhead and alternate between solid stream and high velocity fog for about 30 seconds; then close the compartment door. The water flashes to steam and smothers the compartment.
2. If the seat of the fire can be seen from the door, the nozzle man can use solid stream to hit the fire from the door without ever entering the compartment. This has the advantage of keeping the fire fighters out of the hot gases and smoke in the compartment.
If the compartment is very large then a direct attack must be mounted; the procedure is for the hose men to enter the compartment while staying low to the deck. Do not spray water into the overhead or attempt to cool down bulkheads while making the approach to the seat of the fire. To do this will cause steam to be generated and cause the thermal boundary to be brought to the deck level, making it impossible for the fire fighters to stay in the compartment. It might be best to keep the attack noz­zle shut off during the approach if this is possible. Use only the backup nozzle and applicator for a heat shield and cooling. Once within range of the seat of the fire, apply water vigorously at the seat of the fire until the fire is extinguished. Use only the amount of water necessary to do the job. Remember, you are fighting a fire in a ship and any water you put into the ship must be taken out.
At this point the officer in charge should arrange for bilge suction to be started on the compartment. If this is not possible some form of portable bilge suction should be set up. Drainage from the compartment on fire should be established downward to the bilge or lowest point in the section of the ship being dealt with. Keep in mind that two 11/2-inch fire hoses under 100 psi will discharge one ton of water per minute into the ship. If this rate of flow is allowed to go on long enough without attention, the ship will either capsize or sink.


As crew members arrive at the Emergency Locker, they should start getting prepared with their assigned equipment. This should be automatic and the crew members should not have to be told to do so. The following should be done:
1. Breathing apparatus men don their protective clothing immediate­ly. The protective clothing provided in the locker is called a fireman's outfit. U.S. Coast Guard regulations do not specify exactly what a fireman's outfit is, but it is understood that it is the clothing that a fireman would wear to protect himself from the radiant heat of the fire and the hot gases of the fire. This clothing will include a foul weather gear top and bottom, rubber boots, and rubber gloves.
2. Breathing apparatus men now don their breathing apparatus and place it in the standby mode.
a. For the tank type breathing apparatus such as the Scott Air-Pak, this means the tank strapped on with tank valve open, the regulator set up, and the face mask hung off from the neck or tucked under one shoulder strap. The breathing hose is not yet plugged in.
3. Assigned equipment in the locker is picked up and checked out.
4. The fire fighters leave for the location of the fire.
Emergency Crew at the Scene
When the emergency crew arrives at the scene the officer in charge of the squad will take over from the witness as scene leader. The officer should obtain an update from the witness on the conditions at the scene. This in­formation should include:
1. Whether boundaries have been set and if so then where.
2. Whether boundaries are holding and if not then where the fire is spreading.
3. What closures have been made and ventilation secured.

The officer in charge is now in a position to make a decision on how to fight the fire. He should direct the emergency squad to set up at least two hoses and lead them to the entrance to the area or zone on fire. It is preferable that the setup and the fire station selected be on the weather deck. Usually the interior of the ship is smoked out or about to be smoked out and visibility and breathing conditions are deteriorating rapidly. Inte­rior fire stations should be used only as a last resort and then the farthest interior fire station from the fire should be selected.
It is preferable that the two fire hoses being run out should be led from separate fire stations but where this is not possible then they should be led from a single fire station using a Y-gate. Sufficient lengths of fire hose must be laid out to reach the farthest spot in the fire area to be entered. The number of lengths needed will have been previously determined during mock attack on the area in your weekly fire drills.
One fire hose should be fitted with an all-purpose nozzle and will be used as the attack nozzle. The other hose will be fitted with an all-purpose nozzle and 4-foot applicator and will be used as a backup hose during ap­proach. The fine fog mist from the applicator will provide a heat shield for the fire fighters and also act to cool them during approach.
Each hose must be manned by a nozzle man and backup man. Both men on each hose must be fully dressed out and must be wearing breathing ap­paratus. These men need not be wearing safety lines since their hoses will be used to find their way out if necessary or can be used for rescuers to find their way in to the fire fighters.


The crew member discovering the fire should take the following action:
1. Before leaving the scene, if you can close the door, cover, or damper through which the fire was discovered. If a vent switch is handy shut it off but do not waste time looking for it if you do not know where it is.
2. Notify the bridge of the fire. If there is a sound powered phone or dial phone handy, use it. Otherwise, run to the bridge or the engine room, whichever is closest, and notify them of the fire. Keep in mind that the engine room has a sound powered phone to the bridge as well as a general alarm actuator. Pass the following information:
a. Location of fire-by compartment number if possible or by verbal description or use of the compartment.
b. Type of fire-class of the fire if known.
3. Return to the scene of the fire after passing the word. Keep in mind that the witness knows more about the fire at that moment than any other crew member on the ship. The witness should take charge at the scene until an officer arrives to take over.
1. Keep the fire from spreading. In the case of a major fire it is impor­tant to keep the fire from spreading even if the fire cannot be fought directly. Later as more crew members arrive on the scene an attack can begin. Set boundaries around the fire area:
a. Break out the fire hoses around the area and begin cooling down the boundary bulkheads, the deck area that is the overhead for the compartment on fire, and the overhead of the compartment below, which is the deck of the compartment on fire. Even if the fire cannot be fought directly later on, the fire will not spread once boundaries have been set.
b. Clear flammables away from the boundary bulkheads. Remember that the steel bulkheads surrounding the compartment on fire will get red hot as the fire burns on and any nearby combustible may be in danger of igniting. The combustibles need only be moved away from the bulkheads. Later as more crew members show up these combustibles can be moved farther away.
c. Continue making closures and shutting off ventilation. Locate all vent switches and shut them down. Close covers to vent openings, close portholes, skylights, and any additional rear doors that may still be open.
On the Bridge
Once the word has been received on the bridge, take the following action:
1. Ring the general alarm bell with the signal for Fire and Emergency and at the same time give this signal on the ship's whistle. The sig­nal for Fire and Emergency is the continuous ringing of the ship's general alarm bell for at least 10 seconds supplemented by the same signal on the ship's whistle.
2. Shut down the ventilation for the area involved using the master shut-down switches on the bridge. have a master shut-off switch located on the bridge. This includes vent systems for the berthing spaces, engine room, and the cargo spaces.
3. Start taking notes on what is happening. Jot down the time, the name of the witness if known, the location of the fire, and the type of fire. On the navigation work sheet mark off the ship's position at the time of occurrence. Note this position in the notes. The master will want all of this information when he gets on the bridge.


Fires can be classified into four groups:

Class A-Fires in ordinary combustible materials such as mattresses, dunnage, wood, canvas, etc. These fires are best extinguished by the cooling effects of water or water fog.
Class B-Fires in such as gasoline, oil, lubricating oil, diesel oil, tar, greases, etc. The blanketing or smothering effect of the extin­guishing agent is important.
Class C-Fires in live electrical equipment, such as switchboard insula­tion, transformer terminals, etc. The extinguishing agents must be nonconducting so that electrical shock is not experienced by the firefighter.
Class D-Fires in combustible metals like magnesium, sodium, titanium, lithium, etc.
Except for a fire caused by a catastrophic event, a fire starts out small.
If it is discovered, it can probably be extinguished by one of the portable extinguishers.
Different types of fires require different types of extinguishers. Portable extinguishers are placed aboard ship according to the type of hazard that might be seen in the space where they are located. Por­table extinguishers are first aid measures only and are not intended as a substitute for hose lines when the fire is beyond the limitations of the ex­tinguisher in use. Here are the types of fires for which each por­table extinguisher can be used:

1. Water (stored pressure type). Use on class A fires. Do not use on electrical fires.

How to operate: Break the seal and pull the locking pin. Direct the nozzle at the base of the fire. Grip the lever and squeeze.
Maintenance: Inspect monthly for full pressure and physical condition. Discharge and refill with fresh water annually.
2. Foam (stored pressure type). Use on class Aand class B fires. Do not use on electrical fires.
How to operate: Break the seal and pull the locking pin. Direct the nozzle at the base of the fire. Grip the lever and squeeze.
Maintenance: Inspect monthly for full pressure and physical condition. An­nually discharge and refill with fresh foam solution or replace the foam hose cartridge (depending on design).
3. Carbon dioxide. Use on class B and class C fires. C02 extinguishers are not permitted in passenger and crew quarters.
How to operate: Break the seal and pull the locking pin. Hold the nozzle on the insulated handle, squeeze the lever, and direct the gas at the base ofthe fire.
Maintenance: Inspect monthly for condition of seal and bottle. Weigh the bottle annually. If the net weight without the hose and horn is down by 10 percent of the full charge then the bottle requires recharging. Re-hydro the bottle every 12 years if the bottle did not require recharging during that interval.
4. Halon 1211. Use on class B and class C fires. Some of the larger capacity Halon bottles may have an A rating. Check the face of the bottle for specifics.
How to operate: Break the seal and pull the locking pin. Direct the nozzle at the base of the fire. Grip the lever and squeeze.
Maintenance: Inspect monthly for full pressure gauge reading and physical condition. Check the pressure gauge and weigh the bottle annually. Re­hydro at intervals required by the D.O.T. Interval will depend on the stan­dards to which the bottle was built. Both Halon 1211 and 1301 may be used in portable extinguishers.
5. Dry chemical. The class of fire for which the extinguisher is effective will depend on the dry chemical in it. Check the face of the bottle for specifics.
Sodium bicarbonate and potassium bicarbonate: Use on class B and class C fires.
Mono-ammonium phosphate: Use on class A, class B, and class C fires. How to operate: Depends on the design of the extinguisher.
External cartridge dry chemical type: Pull the hose up sharply to break the seal. Press the activation plunger. Squeeze the lever on the discharge hose to confirm the powder flow before committing to the fire. Discharge the powder at the base of the fire.
Stored pressure type: Break the seal and pull the locking pin. Direct the hose at the base ofthe fire and squeeze the lever.
Maintenance: Inspect monthly for full pressure gauge on stored pressure extinguisher. Inspect all types for condition of hose and container.
6. Dry powder. The term dry powder has been reserved exclusively by the National Fire Protection Association (NFPA) to describe powdered agents which are intended for use on class D fires. The extin­guishing agent must be matched to the class D material of concern. There is no powder that is effective against all of the 26 class D metals. Fire extinguishers are now provided with symbols that are displayed on the bottle to show which type of fire the extinguisher is ef­fective against: A, B, C, or D.

1. Soda acid. Use on class A fires. Do not use on electrical fires.
How to operate: Turn upside down. Direct nozzle at base offire. Recharge. Maintenance: Inspect monthly for condition. Annually discharge and refill.

2. Foam. Use on class A and class B fires. Do not use on electrical fires.
How to operate: Turn upside down. Direct nozzle at base of fire. Recharge. Maintenance: Inspect monthly for condition. Discharge and refill annually.







Although slave ships generally had to be burned after a few voyages so that the odors emanating from below deck would not alert govern­ment agents the Spanish slaver Leon did not meet her end in this way. The Leon's is probably the strangest story in the history of the slave trade.

The Leon's last voyage in 1819 was among the cruelest of slave passages. On such ships only the smallest slaves could stand erect in the hold. Only once or twice were they hosed down with saltwater. Rations were very small to increase the slaver's prof­its. The Leon's crew was probably a happy one, an­ticipating the bonus promised them-until, in mid­passage, every person aboard the ship went blind.

The crew's blindness can be discounted, or at­tributed to diet deficiency or disease, but how can the whole story be explained? The Leon must have passed land time and again in her strange journey, her hardened crew praying for another ship to sight her. The slaver sailed mountainous seas; the pleas of a blind crew were one with those of blind slaves. Gulls cried out, and waves battered the ship. Fi­nally, a voice different than those on board was heard, and the Leon's crew listened intently.

Another slaver had sighted them. Their savior ship approached, and her helmsman hailed them. She was a French ship the Rodeur. The Rodeur got closer. Then she lurched away, her helmsman cursing. He veered the Rodeur toward land, suddenly realizing that the Leon's crew was blind. The men on the Leon soon heard nothing more, and perhaps this was best. For the Rodeur 's helmsman could not possibly have helped them. He had, in fact, been seeking their as­sistance. Except for himself every member of his crew was totally blind.

Every person aboard the Rodeur, including her slave cargo, had gone blind days before, but the helmsman got his ship to a West Indies port and lived to tell his story. Even with his account, how­ever, the Leon was never found.

The Leon's wooden bones have never floated to shore. Some believe that she remains a ghost ship creaking at the sides and forever bemoaning her hor­rible fate, that when the ocean ragt;s up asserting her power, even now pleading voices aboard the Leon can be heard, damned men crying out for salvation, the Leon sailing on, crew and slaves forever equal.




MIDDLE LATITUDE SAILING - Called mid-latitude sailing, combines plane sailing and parallel sailing. Plane sailing is used to find difference of latitude and departure when course and distance are known, or vice versa. Parallel sailing is used to interconvert departure and difference of longitude. The mean latitude (Lm) is used to determine the middle latitude, the latitude at which the arc length of the parallel separating the meridians passing through two specific points is exactly equal to the departure in proceeding from one point to the other. The formulas for these are:

DLo = p sec Lm

p = DLo cos Lm

The mean latitude (Lm) is half the arithmetical sum of the latitudes of two places on the same side of the equator. The mean latitude is labeled N or S to indicate whether it is north or south of the equator. If a course line crosses the equator, that part on each side (the north latitude and south latitude portions) should be solved separately. This sailing, like most elements of navigation, contains certain approxi­mations which produce answers somewhat less accurate than those by more rigorous solutions. For ordinary purposes, the results are more accurate than the navigation of the vessel using them. From time to time suggestions have been made that a correction be applied to eliminate the error introduced by assuming that the meridians of the point of departure and of the destination converge uniformly (as the two sides of a plane angle), rather than as the sine of the latitude (approximately). The proposed correction usually takes the form of some quantity to be added to or subtracted from the middle latitude to obtain a "corrected middle latitude" for use in the solution. Tables giving such a correction have been published for both spherical and spheroidal earths. The actual correction is not a simple function of the middle latitude and the difference of longitude, because the basic formulas of the sailing are themselves based upon a sphere, rather than a spheroid. The use of such a correction is misleading, and may introduce more error than it eliminates.

Example - A vessel steams 1,253.0 miles 0n course 070 from Lat. 15-17.0 N, Long. 151-37.0 E.

Required - (1) Latitude and (2) Longitude of the point of arrival.

Solution - By computation: (1) l = D cos C; p = D sin C (2) DLo = p sec Lm.

To see solution go to "CLICK HERE TO VIEW FORM" for MID - LATITUDE FORM

Thursday, November 29, 2007


The static stability of a ship is the measure of her tendency to return to the upright after being inclined by external forces such as wind or waves. A ship's stability is influenced by her underwater form, or shape, and by the amount and position of the weights or loading placed aboard the ship. Determining the dimensions, proportions, and shape of the hull for stability in a properly loaded ship is the business of the ship designer. It is the ship's Master and Chief Mate, who have control over her loading. You must understand the basic principles of stability to avoid loading conditions that will produce too little or too much of it. There are several programs out that help in working with stability, this is just some basic things that are good to know.
WEIGHT AND BUOYANCY - A ship when afloat is acted on by two princi­pal forces, its weight and its buoyancy, that are equal to each other but act in opposite directions. The weight acts downward through a point called the center of gravity. The buoyancy acts upward through the center of buoyancy.

To find the height of the center of gravity of a ship above the keel a very simple principle is used, but it can be complex and time consuming. The weight of each sizeable piece of hull or machinery is multiplied by its distance above the keel. This gives a number of things when added together equal the moment sum. The sum of the weights of all these parts is also made and is the total weight of the ship, This is called ships displacement. Height of the ship's center of gravity above the keel is the moment sum divided by the ship's displacement.

DISPLACEMENT - Should a graving dock be filled with water to the top of the gates and a launch lowered by crane into the water some water will then flow over the top of the gates. If this water is caught in tanks and weighed the weight will be found to be the same as the launch. And the volume is the same as the underwater part of the launch. In other words the vessel removes or displaces a weight of water equal to its own weight. I should mention a displacement ton is 2,240 pounds. The relation of the volume of the underwater part of the vessel to a rectangular block of the same length, beam, and depth is called the fineness coefficient. The displacement of a vessel is then the product of the length, beam, draft, and fineness coefficient all di­vided by thirty-five. In ship stability calculations the center of gravity of the volume of the underwater part of the ship is very important.

The posi­tion of this center of buoyancy fore and aft is called the longitudi­nal center of buoyancy. The position of the center of buoyancy measured in a vertical direction above the keel, or in some cases from the plane of water line is called the vertical center of buoyancy. The same is true of all the usual surface ships.
WORKING BUOYANCY - is the amount of buoyancy available for carrying of cargo, that is the difference in displacement in tons between the ship when light and when loaded down to the Plimsoll mark.

The center of buoyancy curve is a curve showing the height of the vertical center of buoyancy for various drafts of the ship. The freeboard of a ship is the distance from the top of the freeboard deck to the water line. The freeboard deck is the uppermost com­plete deck having permanent means of closing all openings in weather portions of the deck. Freeboard is measured at the center of the ship and if necessary the top of the freeboard deck plank is continued through the water way.

SPECIFIC GRAVITY - is the weight of a given number of cubic inches of a given material divided by the weight of the same number of cubic inches of water. Inertia is the tendency of a body in motion to continue in mo­tion, and if at rest to continue at rest. The moment of inertia of a plane about an axis is the sum of the products of each small part of the surface multiplied by the square of the distance of each part from the axis.
The polar moment of inertia which is used for period of roll is the sum of the weights of all parts of the ship multiplied by the squares of each individual distance from a horizontal line passing fore and aft and through the ship's center of gravity.
The longitudinal metacenter is similar to the transverse meta­center except in a fore-and-aft direction but is not of much im­portance because the period of pitching is so very small compared with the periods of the waves that there is no synchronism set up. The period of seconds of a complete roll of a ship, that is a roll from port to starboard and back to port again
SYNCHRONISM - Is the condition resulting from waves reaching the ship in such succession that each catches the ship at the same period of roll and results in a rapidly increasing amplitude. This can be­come so dangerous that to avoid it the ship's course must be changed.
METACENTRIC CURVES - Are curves showing the heights above the keel of metacenters and centers of buoyancy for varying dis­placements of the ship.
METACENTRIC HEIGHT - Transverse metacentric height is a meas­ure that determines a ship's initial stability. The larger it is in posi­tive value the "stiffer" the ship will be. Should it be too great the ship will be very uncomfortable and if it is too small the ship will be "tender" and her safety may not be what it should be.The distance between the two lines is called righting lever. Which is a kind of force tending to right the ship at any time, is the displacement of the ship multiplied by its righting lever.
WEDGE OF IMMERSION - is the wedge of the ship which will be immersed when the ship is inclined and the wedge of emersion is the corresponding wedge of the ship on the opposite side which will emerge from the water during the operation.
The distance between the center of buoyancy and the transverse metacenter equals the mo­ment of inertia of the water plane about its center line.
TONS PER INCH OF IMMERSION - is given in curves showing the dis­placement change for every inch of increased draft.
Stability studies relate to the tendency of a ship when inclined to resume its upright position. Statical stability is the product of the righting arm multiplied by the displacement.
INITIAL STABILITY - is the stability of a ship at small angles of in­clination as measured by metacentric height and displacement. The curve of stability is a curve giving the righting lever in feet for various large angles of inclination.
RANGE OF STABILITY - is the angle of ship's heel in degrees at which the righting arm disappears and a ship is just as likely to capsize as to right itself. This is only of meaning if all openings by which flooding can take place are closed, and is in general greatest in ships of large freeboard.
DYNAMICAL STABILITY - of a ship is the work done in inclining the ship to any angle and equals the displacement multiplied by the increased vertical separation of the centers of gravity and buoyancy of the ship from upright to an inclined position.
For every ship stability curves are worked out for various drafts and loadings.

The longitudinal metacentric height is computed similarly to the transverse metacentric height except that in computing the moment of inertia of the water plane is taken about an athwartshlp axis passing through or directly above the center of gravity. The longitudinal metacentric height is used in calculating changes of trim. A change of trim is the sum of the change of drafts forward and aft and changes of trim can be caused by a shift of weights on board in a fore-and-aft direction.



For over 300 years the story of the Flying Dutch­man trying to round the Cape of Good Hope against strong winds and never succeeding, then trying to make it past Cape Horn and failing there too, has been the most famous of maritime ghost stories. The cursed spectral ship sailing back and forth on its endless voyage, its ancient white-haired crew crying for help while hauling at her sails. One superstition has it that any mariner who sees the Flying Dutch­man will die, and many are said to have expired this way. Another old yarn has it that the ghost ship disappears into a storm as soon as another ship gets within hailing range. The ship, which supposedly sailed in about 1660, has been called a schooner, a sloop, and a merchant, and no descrip­tion of her is ever the same. Her wicked captain, whose story this really is, is said to have been named Vanderdecken, Fokke, or Van der Staaten, and there is no historical record of either him or his ship.

Once upon a time, a good many years ago, there was a ship's captain who feared neither God nor His saints. He is said to have been a Dutchman, but I do not know. He happened once to be making a voyage to the South. All went well until he came near land. It was his boast that no storm, however terrible, could make him turn back.
On one voyage to the South at the Cape of Good Hope, he ran into a head wind that might have blown the horns off an ox. Between the wind and the great waves the ship was in mortal danger. Everyone aboard argued with the captain to turn back.
"We are lost if you don't turn back, Captain!" they said. "If you keep trying to round the cape in this wind, we shall sink. We are all doomed, and there isn't even a priest on board to give us absolution before we die." The captain only laughed at the fears of his passengers and crew. Instead of heeding them, he broke into songs so vile and blasphemous that just by themselves they might have drawn the lightning to strike the masts of the ship. Then he called for his pipe and his tankard of beer, and he smoke and drank as unconcernedly as though he were safe and snug in a tavern back home.

The others renewed their pleas for him to turn back, but the more they begged him the more obstinate he became. The wind snapped the mast the sails were carried away, and he merely laughed and jeered at his terrified passengers.
Still more violently the storm raged, but the captain treated with equal contempt the storm violence and the fears of his crew and passenger; When his men tried to force him to turn and take shelter in a bay, he seized the ringleader in his arms and threw him overboard. As he did this the clouds opened and a Shape alighted on the quarter deck of the ship. This Shape may have been the Almighty Himself or was certainly sent by Him. The crew and passengers were struck dumb with terror. The captain, however, went on smoking his pipe and did not even touch his cap as the Shape spoke to him.
"Captain," the Shape said, "you are a very obstinate man. "
"And you," cried the captain, are a rascal who wants a smooth passage, Not I, I want nothing from you, so clear out and leave me unless you care to have your brains blown out. "
The Shape shrugged his shoulder without answering.
The captain snatched up a pistol, cocked it, and pulled the trigger. The bullet, however, instead I reaching its target turned and went through his hand. He leapt up to strike the Shape in the face. But even as he raised his arm, it dropped limply at his side, though paralyzed. In helpless anger then he cursed and blasphemed and called the heavenly Shape, kinds of evil names.
At this the Shape spoke to him.
"From this moment on, you are accursed. You are condemned to sail forever without rest, without anchorage, without making port of any kind. You shall never taste beer or tobacco again. Your drink will be gall, your meat will be red-hot iron. Only a cabin boy will remain of all your crew. Horns will grow from his forehead, and he will have a tiger's face and skin rougher than a dog fish's. "
At this the captain, sobered at last, groaned. The Shape continued.
"It will always be your watch, and you will never be able to sleep, no matter how you long for it. The moment you close your eyes a sword will pierce your body. And since you delight tormenting sailors, you shall torment them for ever more."
At that the captain smiled.
The Shape said to him, "You shall be the evil spirit of the sea. You will travel all oceans and all latitudes without stopping or resting, and your ship will bring misfortune to all who sight it. "
"Amen to that!" the captain cried and laughed. "And on Judgment Day, Satan will claim you for his own. "
"A fig for Satan!" the captain answered.
The Shape vanished, and the Dutchman found himself alone with his cabin boy, who had already changed to the evil appearance that had been fore­ told. The rest of the crew had vanished.
From that day to this the Flying Dutchman has sailed the seas, and he takes malicious pleasure in tricking unlucky mariners. He sets their ships on false courses, leads them onto uncharted shoals, and shipwrecks them. He turns their wine sour and changes all their food into beans. Sometimes he will pretend to have an ordinary ship and will send letters on board other ships he meets at sea. If the other captain is so unfortunate as to try to read them, he is lost.
At other times an empty boat will draw along­side the phantom ship and vanish, a sure omen of bad luck to come. The Flying Dutchman can change the appearance of his ship at will, so that he cannot be recognized, and through the years he has collected around him a new crew. Every one of them comes from the worst criminals, pirates, and bullies of the world's oceans, and every one of them is as cursed and doomed as he himself.

Wednesday, November 28, 2007



The magnetic compass is one of the oldest of the navigator's instruments. Initially, a compass was used only to indicate north, but soon the concept of marking other directions around the rim of the bowl was thought of. The directions were given the names of the various winds, now known as North, East, South, and West; these are the cardinal directions. Next are the intercardinal directions: NE, SE, SW, and NW. Still finer subdivisions are the combination directions: NNE, ENE, ESE, etc.; and the by-points: NxE, NNExN, NNExE, etc. This system results in a complete circle divided into 32 points and there are half-points and quarter points. The point system was widely used until relatively modern times, but is now obsolete except for some minor use on sailing craft.

Because of the difficulty at sea in using a needle floating freely in an open bowl of water, the next development was that of using a pivot at the center of a dry bowl. Not for some centuries was the liquid put back in, this time in an enclosed chamber, as now is the case in modern magnetic compasses.

The magnetic compass still retains its importance, despite the in­vention of the gyrocompass. While the gyro is an extremely accurate instrument, it is highly complex, dependent on an electrical power supply, and subject to mechanical damage. The magnetic compass, on the other hand, is entirely self-contained, simple, comparatively rugged, and not easily damaged.


1. A parallax correction is NOT applied to observations of the ? Stars.

2. What sextant correction corrects the apparent altitude to the equivalent reading at the center of the Earth ? Parallax.

3. Astronomical refraction causes a celestial bodv to appear ? Lower than its actual position.

4. The error in a sextant altitude caused by refraction is greatest when the celestial body is ? Rising.

5. The error in the measurement of the altitude of a celestial body, caused by refraction, increases as the ? Altitude of the body decreases.

6. The correction tables in the front of the Nautical Almanac for use with Sun sights do NOT include the effects of ? Mean refraction.

7. The correction tables in the Nautical Almanac for use with Moon sights do NOT include the effects of ? Augmentation

8. An amplitude of the Sun in high latitudes ? Is most accurate when the Sun's center is observed on the visible horizon.

9. When taking an amplitude, the Sun's center should be observed on the visible horizon when ? The Sun is near or at a solstice.

10.The center of a circle of equal altitude, plotted on the surface of the Earth, is the ? Geographical position of the body.


The draft of a vessel is the distance that it is immersed in the water or the depth from the bottom of the keel to the water line.
Draft marks are painted on both sides of the stern and rudder post in the following manner: The numerals are six inches high with six inches space between them and the bottom of each numeral rest on an even foot of draft. This method makes it possible to estimate by eye the inches of draft, if the water covered half a number the

draft would be equal to that number of feet plus 3 inches.

The freeboard of a vessel is the height above the water level to the top of the freeboard deck measured amidships.
A load line is a line that limits the maximum mean draft so that there will be sufficient freeboard and reserve buoyancy to insure the safety of the vessel. The position of the load line on American ships is determined by the American Bureau of Shipping and indi­cated on the sides of the hull by Plimsoll marks. Plimsoll marks consist of a disk with a horizontal line through its center, indicating the summer load line, and a series of other horizontal lines indicating the load lines for various waters and seasons. The abbreviations used to mark these lines are :










LENGTH OVERALL - is the extreme length measured from the foremost part to the aftermost part of the hull.

LENGTH BETWEEN PERPENDICULARS - is the length measured between the forward part of the stem to the after part of the rudder post. In the case of a raked stern or rudder post the measurement is taken from the intersection through the upper deck.

LENGTH REGISTERED - is the length measured between the forward part of the stem and the after part of the stern post.

BREADTH MOLDED - is the breadth of the hull at the widest part, measured between the outer surfaces of the frames.

BREADTH REGISTERED - or extreme breadth is the breadth of the hull at the widest part measured between the outer surfaces of the shell plating.

DEPTH MOLDED - is the depth measured between the top of the keel, or lower surface of the frame at the center line, and top of the upper deck beam at the gunwale, or to the top of the second deck beam in a shelter or awning deck vessel.

DEPTH REGISTERED - is the depth measured amidships between the top of the double bottoms or top of floors, and the top of the upper deck beams, or second deck beams in a shelter or awning deck vessel.


DISPLACEMENT TONNAGE - is the actual weightof the entire vessel and evey thing aboard her measured in long tons in long tons (2240 lbs.). The displacement tonnage is equal to the weight of the water displaced by the vessel and varies with the draft of the vessel. Displacement tonnage may be qualified as Light, indicating the weight of the vessel without cargo, fuel or stores; or Heavy indi­cating the weight of the vessel fully loaded with cargo, fuel and stores.

DEAD WEIGHT TONNAGE - is the actual carrying capacity of a vessel and is equal to the difference between the Light 'displacement ton­nage and the Heavy displacement tonnage.

Gross tonnage - is the internal capacity of a vessel measured in units of 100 cubic feet.

NET REGISTERED TONNAGE - is also the internal capacity of a vessel measured in units of 100 cubic feet but does not include the space occupied by boilers, engines, shaft alleys, chain lockers, officers


Ship construction as we find it today is the result of centuries of experience. The main structure of a ship is composed of a multitude of parts that are for strength, watertightness and safety. No space can be wasted and weight must be kept as low as pos­sible, the structural design and arrangement has developed in such way that most of the parts serve at least two purposes and some­times more.
A ship may be considered as a huge box girder, the sides of which are composed of the shell plating and the decks. These parts are in turn strengthened by such members as the keel, frames, beams, keelsons, stringers, girders, and pillars. To appreciate the ship as a whole, it is good to understand the func­tions of each of the parts.
The keel is the backbone about which the ship is built.
It is of a rigid fabrication of plates and structural shapes which run fore and aft along the centerline of the ship. At the for­ward end is connected the stem, and at the after end the stern frame which supports both the rudder and the propeller.

The frames are the ribs of the ship. Their lower ends are at­tached at intervals along the keel, and their upper ends are at­tached through brackets to the beams which support the deck. Internal bracing is provided by keelsons and stringers which run fore and aft. The frames must determine the form of the ship and support and stiffen the shell plating.

The shell plating, although necessary for watertight­ness, is one of the principal strength members of the ship. Running continuously from the stem to the stern frame and from the keel
to the weather deck, it forms three of the sides of the box girder. The plating, along with frames, must be able to withstand the pressure of the water outside and the stresses which arise due to the waves or rubbing against a dock.

The main deck of the ship forms the fourth side of the girder and the reason is that it must be of strong construction. The plating is connected to beams which extend from side to side across the ship. The deck is specially strengthened by doubling plates in the regions where it is weakened by openings such as hatchways, and compan­ionways, and also under all deck machinery, chocks, and bits. The deck is supported from below by girders and pillars.
The bottom, sides, and main deck of the ship, would not be strong enough to stand the stresses of an ocean voyage without some internal stiffening. This is provided by the lower decks and the main transverse bulkheads.
In addition to support for the shell and decks, the main transverse bulkheads are made watertight, and subdivide the vessel into watertight compartments, so that in the event of
damage, the water can be confined. All doors through these bulk­heads must be fitted with gaskets so that they can be made water­tight, and must be kept clear at all times so that they can be closed. The first bulkhead aft of the stem is known as the collision bulk- head as its purpose is to limit the flooding that might occur after a collision. No doors or other openings are permitted in this bulk head below the main deck.

Further protection against damage is provided by the double bottom tanks. These are formed by a second complete layer of watertight plating located a few feet above the outer bottom and extending from bilge to bilge. Any grounding or similar damage which merely pierces the bottom plating will flood one or more of these tanks instead of allowing water to enter one of the main holds. Under ordinary service conditions these tanks are used to carry fresh water, fuel oil or salt water ballast.
The engine and boiler rooms are usually located amidships. These necessary for the support of the engines and boilers. In order to provide sufficient headroom for the propelling machinery, it is usually necessary to omit one or more of the decks. To maintain the vessel's strength in the absence of these decks, several extra heavy web frames and transverse hold beams are fitted.
The propeller shaft extends through the after holds from the engine to the stern gland. As this must be accessible at all times for inspection and lubrication, it is enclosed in a narrow tunnel known as the shaft alley. The entrance to the shaft alley from the engine room is closed by a watertight door, and the sides are of watertight construction so that a fracture of the tail shaft or similar accident will cause only the tunnel to be flooded.

The necessity for good drainage requires special attention in the design and construction of a ship. Free water on the decks, in a hold, or in the bilges is detrimental to the stability of the vessel. The drainage system must be as efficient as possible.
The decks are cambered to permit drainage to the scuppers which lead the water either overboard or to the bilges. Sufficient scuppers and suction must be provided so that the drainage will be effective in any condition of list or trim of the ship. Solid bul­warks, where fitted around a deck, are pierced by large freeing ports to allow any water that is shipped to escape.


The combinations of flags and pennants are hoisted at shore stations to indicate the presence or future presence of unfavorable winds. The meaning of these are:

SMALL CRAFT WARNING: One red pennant ­displayed by day, and a red light over a white light at night to indicate that winds up to (33 knots) and sea conditions dangerous to small craft.

GALE WARNING: Two red pennants by day and a white light above a red light at night to indicate that winds ranging from (34 to 47 knots) are forecast for the area.

STORM WARNING: A single square red flag with a black center displayed during daytime and two red lights at night to indicate winds (48 knots and above) are forecast.

HURRICANE WARNING: Two square red flags with black centers displyed by during the day and a white light between two red lights at night,to indicate that winds 64 knots and above are forecast.


Fronts are weather systems that are sometimes called waves. Along the front, two air masses of widely different characteristics fight a battle for supremacy. Usually the colder of the two masses, being heavier, predominates, forcing the warm air upward. Cold air behind a cold front displaces the warm air ahead of it upward. The warm air behind a warm front moves upward over a retreating cold air mass. When a cold front moves faster than the warm front, it overtakes the warm front, forcing the warmest air masses upward. When these fronts converge, the remaining front on the surface is called an occluded front.
A cold front or a warm front may extend for hundreds of miles long, but the area in which frontal weather disturbances take place is usually a band 15 to 50 miles wide for a cold front and up to 300 miles for a warm front. The point where the cold and the warm fronts converge is frequently the center of a low-pressure area.

When a cold front is coming your Way, the first change you notice is darkening of the horizon to the west and to the north. Very soon the cloud ceiling lowers and rain begins. A fast-moving cold front (which can move 720 miles in a day), with typical cumulonimbus clouds preceding it, brings sudden violent showers or thunderstorms. If the cold front is not preceded by cumulonimbus clouds, the rainfall is steady. Passage of the cold front is usually marked by a wind shift, a drop in temperature, a rise in pressure, and a rapid clearing of the sky condition and visibility.

A warm front, headed by cirrus clouds, is followed (in order) by cirrostratus, altostratus, then nimbostratus and possibly stratus clouds. Visibility is poor in advance of a warm front; frequently fog forms and steady rain or drizzle prevails. Thunderstorms may develop ahead of this front. The frontal line is passing when a marked shift occurs in the wind direction, and the temperature of the atmosphere rises sharply. Gradual clearing takes place and remains steady or falls slowly.


The atmosphere always contains in greater or smaller amounts tiny particles, such as dust from roads, desert sand, plant pollen, salt particles from oceans, and factory smoke. These fragments are hygroscopic "particles that readily absorb moisture." A cloud is merely a mass of hygroscopic nuclei that have soaked up moisture from the air.
The heat generated by the Sun's energy causes earthbound moisture to evaporate (turn into water vapor). Water vapor is one of the gases that make up the atmosphere. Water vapor is lighter than air, and it rises. If the air it passes into is cold the vapor condenses, and turns back into moisture. The water droplets that come from this process cling to the hygroscopic nuclei. These water-soaked nuclei bunched together form a cloud. Fog is the same principle but it's a cloud on the ground.
Changes in atmospheric conditions account for the different shapes of clouds and for
their presence at various altitudes. Formations of the clouds give a clue on the forces at play in the atmosphere.

CIRRUS (CI) clouds are detached clouds of delicate and stringy appearance, white in color, without shading. They appear in varied forms, isolated tufts, lines drawn across the sky, branching featherlike plumes, and curved lines ending tufts.
Cirrus clouds are composed of ice crystals. Before sunrise and after sunset, cirrus clouds may still be colored bright yellow or red. Being high-altitude clouds, they light up before lower clouds and fade out much later. Cirrus clouds indicate the direction in which a storm may lie.

CIRROCUMULUS (CC) Cirrocumulus clouds are commonly called "mackerel sky" look like rippled sand,or like cirrus clouds containing globular masses of cotton. Cirrocumulus clouds are a indication that a storm is probably approaching.
CIRROSTRATUS (CS) Cirrostratus clouds are a thin whitish veil which does not blur the outlines the Sun or Moon, but gives rise to halos (colored or whitish rings and arcs around the Sun or Moon, the colored arcs apear reddish on the inside edges.) A milky veil of fog (thin stratus) lnd altostratus are distinguished from a veil or cirrostratus of similar appearance by the halo phenomenon, which the Sun or Moon nearly always produces in a layer of cirrostratus. The appearance of cirrostratus is a good indication of rain.
Altocumulus clouds are a layer (or patches) composed of flattened globular masses, the smallest elements of the regularly arranged layer being fairly small and thin, with or without shading. The balls or patches usually are arranged in groups, in lines, or in waves. Sometimes a corona (similar to a halo but with the reddish color on the outside edges) may be seen on the altocumulus. This cloud form differs from the cirrocumulus by generally having larger masses, by casting shadows, and by having no connection with the cirrus forms. When followed by cirrocumulus, a thunderstorm is nearing.
Looking like a thick cirrostratus, but without halo phenomena, the altostratus is a fibrous veil or sheet, gray or bluish in color. Sometimes the Sun or Moon is obscured completely. At other times they can be vaguely seen, as through ground glass. Light rain or heavy snow may fall from a cloud layer that is definitely altostratus.

Nimbostratus clouds are a dark gray colored amorphous (shapeless) and rainy layer of cloud. They usually are nearly uniform and feebly illuminated, seemingly from within.
When precipitation occurs, it is in the form of continuous rain or snow, but nimbostratus may occur without rain or snow. Often there is precipitation that does not reach the ground; in which cases, the base of the cloud usually looks wet because of the trailing precipitation.
In most instances the nimbostratus evolves from an altostratus, which grows thicker and whose base becomes lower until it becomes a layer of nimbostratus. When precipitation falls continually, the base of the cloud may extend into the low cloud family range.

Stratocumulus clouds are a layer (or patches) of clouds composed of globular masses or rolls. The smallest regularly arranged elements are fairly large. they are soft and gray, with dark spots.
Underneath stratocumulus waves or strong winds occur. Under the thick parts up-currents rise. Above the cloud layer the air is smooth, but it is turbulent below.

Stratus clouds are a low uniform layer of clouds, resembling fog, resting on the ground. A veil of stratus sky gives a hazy appearance. Usually, only drizzle is associated with stratus. When there no ­precipitation, the stratus cloud form drier than other similar forms, and it shows some contrasts and some lighter transparent ­parts. CUMULUS (CU)
Cumulus clouds are dense clouds with vertical development. Their upper ­surfaces are dome-shaped and exhibit rounded projections, and their bases are horizontal. Stratocumulus clouds resemble ragged cumulus clouds in which the parts show constant change. Strong updrafts exist under and within all cumulus formations.

Cumulonimbus clouds are heavy masses of cloud, with towering vertical devlopment, whose cumuliform summits resemble mountains or towers. Their upper parts
have a fibrous texture, and often they spread out in the shape of an anvil.
Cumulonimbus clouds are generally associated with showers of rain or snow, and sometimes produce hail. They often are associated with thunderstorms.
Most of the cloud types are shown at their average height. The bases of the cumulonimbus may be anywhere from 1600 feet to 6500 feet. Although you would never see all types at anyone time in nature, you may observe two or three layers of clouds of different types at one observation.


You may have thought of a cyclone as being always a violent windstorm. Meterologists use this term for any low-pressure area. The furious, destructive disturbance (called a typhoon in the Orient, and a hurricane in the West Indies) is referred to sometimes by weather experts as a tropical cyclone. Fully developed, the tropical cyclone consists of a well-defined area, more or less circular in shape, which the atmospheric pressure diminishes rapidly on all sides toward the center.
Within this area the winds blow with great force. Rainfall is very heavy, especially toward the center. The motion of the air suggests on a gigantic scale the path followed by air in a whirlwind or water in a waterspout. Winds circulate counterclockwise around the center in the northern hemisphere, clockwise in southern hemisphere. At the center itself (the eye of the storm) the dense canopy of clouds overhang the rest of the storm a and calm or light air is seen, but sea here is usually very heavy.
Tropical cyclones occur in the North Atlantic, the North and South Pacific, and the Indian Ocean. Due to the proximity of African and South American land masses the South Atlantic is free of these disturbances. The general track of a tropical cyclone in the northern hemisphere is a line running westward from the point of origin, then curving toward the north, and then recurving to the northeast. By this time it probably has reached middle latitude, and beyond this point it us loses its force and is spent.


In high-pressure area, the air at the center the air at the center flows outward. In a low, the air flows inward. This flow is not, strictly outward or inward. The Earth's rotation deflects the air, so that in reality it flows more or less tangent to the isobars. In the northern hemisphere this almost circular movement of the air is clockwise and away from the center of a high, but counterclockwise and toward the center of a low. In the southern hemisphere, the reverse movement occurs.
The little symbols that cross the isobars indicate wind direction and velocity. They're like arrows except that they have no head and only half a tail. The long arm of each symbol points, like an arrow, in the direction of the wind flow. Some of the symbols have one tail feather, some two, and some three. Each long feather represents 10 knots of wind; each short feather, 5 knots. A arrow with one long and one short feather indicates wind velocity of 15 knots; an arrow with four long feathers indicates 40 knots of wind.
The flow of air is influenced not only by the pressure and the Earth's rotation but also by friction against the Earth's surface. This friction, which slows down air motion, is greatest over land areas, especially where there is abrupt mountainous terrain. As the air within the low or the high rotates the whole circulation of air also moves. Consider the weather charts for several days in a row. On the first day a low may appear over the Pacific Coast region. The chart for the next day probably shows it somewhere in the Rocky Mountain region. A day or two later it may be over Arkansas. If it has not broken up by this time, it moves on eastward and northward, and eventually dissipates over the North Atlantic. All lows in the United States do not follow this same track.


A chart of the atmospheric pressure over a large area of the Earth's surface at any given time tells you which way different air masses (masses of air which have common temperature and humidity characteristics) are moving. Some air masses originate in the cold polar regions; some in the tropics. By the time they reach you, some air masses have moved from large bodies of water (called maritime air masses). Others (called continental air masses) have grown up over more or less dry land.
Air masses carry along with them the temperature and humidity characteristics of the areas they crossed. Where distinctly different air masses touch, the boundary between them is called a front and is marked by cloudiness and precipitation.

The atmosphere can produce weather in other ways, but frontal weather, can be violent, and can be predicted from a chart of the pressure systems. Atmospheric pressure is reported in inches of mercury or millibars. One atmosphere equals 14.696 psi, a bar equals slightly more than 0.98 atmosphere, and a millibar equals 1/1000 of a bar. On weather charts pressure usually is indicated in millibars. The atmosphere can produce weather in other ways, but frontal weather, which usually is violent can be predicted from a chart of the pressure systems. Atmospheric pressure is reported in inches of mercury or millibars. One atmosphere equals 14.696 psi, a bar equals slightly more than 0.98 atmosphere, and a millibar equals 1/1000 of a bar. On weather charts pressure usually is indicated in millibars. Isobars never join or cross. Some may off the chart, but others may close, forming irregular ovals that define the areas of highest and lowest pressure. Air flows from high-pressure areas to low pressure areas areas. The strength of the wind depends on two things, the amount of difference in pressure and the distance of the high-pressure area from the low-pressure area. All these factors combined are called pressure gradients. The greater the gradient, the stronger wind. Isobars can give a rough indication of the amount of wind. The closer an isobar is to another, the stronger the wind in that area.
Widely separated isobars indicate light winds,isobars closer together mean greater wind velocity. Isobars are always tied-out curves, usually making irregular ovals about the high- or low-pressure center. The greatest pressure is at the system center.


Consists of determining the direction from which the wind is blowing and the speed of the wind. Wind direction is measured by a wind vane, and wind speed by an anemometer.
A wind vane is a device pivoted on a vertical shaft with more surface area on one side of the pivot than on the other, so that the wind exerts more force on one side, causing the smaller end to point into the wind.
A anemometer consists of cups mounted on short horizontal arms attached to a longer vertical shaft which rotates as the wind blows against the cup.

You can use a Maneuvering Board to determine both your speed and direction of the true wind by means of the speed triangle.
Apparent wind is the force and the relative direction from which the wind blows, as measured aboard a moving vessel. It can also be expressed as a true direction.
In this triangle, the vector (er) represents the course and speed of the ship, the vector (ew) the direction and speed of the relative or apparent wind, and the vector (ew) is the direction and speed of the true wind. The vector (er) is plotted first, the vector (rw) is then plotted from (r) in the direction the apparent wind is blowing, the length of (rw) represent the speed of the apparent wind. The third vector (ew) represents the direction and speed of the true wind. True wind is the force and true direction from which the wind blows, as measured at a fixed point on the earth.
Here is a example, your ship is underway, on course 030°, speed 15 knots, and the true direction of the apparent wind is 062° at 20 knots.
Draw the speed triangle as using a scale of 2: l.
The vector (er) represents your course and speed. From (r) plot the rela­tive speed vector (rw) in the direction of 242° (the apparent wind direc­tion, 062° plus 180°), and to a length representing 20 knots, this is labeled (w) join (e) and (w) this vector, (ew) repre­sents the true wind direction, from 109.5°, and its speed, 10.8 knots.


Any inaccuracy of the instrument can be determined by comparison with a precision instrument, the National Weather Service provides a comparison service. The shipboard barometer should be corrected for height, before comparison If there is reason to believe that the barometer is in error, you should be compare it to a standard, and if an error is found, the barometer should be adjusted to the correct reading, or a correction applied to all your readings.
The atmospheric pressure reading at the height of the barometer is called the station pressure and is subject to a height correction in order to make it a sea level pressure reading. Isobars reflect wind conditions of pressure only when they are drawn for pressure at constant height or the varying height at which a constant pressure exists.

Mercurial barometers are calibrated for standard sea level gravity at latitude 45 °32' 40". If the gravity differs from this amount,their is a error. The correction to be applied to readings at various latitudes is in Bowditch table 12.
Barometers are calibrated at a standard temperature of 32 degrees. The liquid of a mercurial barometer expands as the temperature of the mercury rises and contracts as it decreases. The correction to adjust the reading can found in Bowditch table 13.

Tuesday, November 27, 2007


ATMOSPHERIC PRESSURE - The layer of atmosphere that surrounds you exerts a pressure of about 15 pounds per square inch at the Earth surface. The weight of the atmosphere varies with the presence of water vapor as with temperature and height above the earth's surface. Variations in atmosphic pressure are measured by an instrument called a barometer.
Consists of a glass tube a little more than 30 inches in length the tube is filled with mercury and inverted into a cup of mercury. The mercury in the tube falls until the column is supported by the pressure of the atmosphere on the open cup, leaving a vacuum at the upper end of the tube. The height of the column indicates atmospheric pressure.The mercurial barometer is subject to rapid variations in height, called pumping due to pitch and roll of the vessel and temporary changes in atmospheric pressure in the vicinity of the barometer. Most of these barometers have been replaced at sea by the aneroid barometer.

The aneroid barometer measures atmospheric pressure of the force exerted by the pressure on a partly evacuated, thin-metal element called a sylphon cell (aneroid capsule). A small spring is used either internally or externally to counteract the tendency of the atmospheric pressure to crush the cell. Atmospheric pressure is indicated directly by a scale and a pointer connected to the cell by a combination of levers.
An aneroid barometer should be mounted permanently. Before putting to use, you should set it to station pressure, a adjustment is provided for this purpose. The error in the reading of the instrument is determined by comparison with a mercurial barometer or a standard aneroid barometer. If you can't find a meteorologist available to make this adjustment, it is a good idea to remove only one-half the apparent error. The case should then be tapped lightly to assist the linkage to adjust itself. If the remaining error is not more than half a millibar (0.015 inch), no attempt should be made to remove it by further adjustment.

The barograph is a recording barometer. Basically it is the same as a nonrecording aneroid barometer except that the pointer carries a pen at its outer end, and the scale is replaced by a slowly rotating cylinder and a prepared chart is wrapped around this. A clock mechanism inside the cylinder rotates the cylinder so that a continuous line is traced on the chart to indicate the pressure at any time.

A marine microbarograph is a precision barograph with greater magnification of deformations due to pressure changes. Two sylphon cells are used, one being mounted over the other in tandem. Minor fluctuations due to shocks or vibrations are eliminated by damping. Since oil-filled dashpots are used for this purpose, the instrument should not be inverted.
The barograph is usually mounted on a shelf or desk in a room open to the atmosphere, and in a location which minimizes the effect of the ship's vibration. Shock absorbing material such as sponge rubber is placed under the instrument to minimize shocks.
The pen should be checked and the ink well filled each time the chart is changed. Every week in the case of the barograph, and each 4 days in the case of the microbarograph. The dashpots of the microbarograph should be kept filled with dashpot oil within three-eighths inch of the top.
Both instruments require checking from time to time to insure correct indication of pressure. The position of the pen is adjusted by a small knob provided for this.


PSYCHROMETER - A psychrometer is simply two ordinary thermometers mounted together on a single strip of material. The bulb thermometer is covered by a water-soaked wick from which the water evaporates rapidly slowly, depending on the amount of water in the surrounding atmosphere. Evaporation of water around the wet thermometer cools it. The amout of cooling depends on the rate of evaporation. The reading on the wet bulb is lower than the reading on the dry bulb except when the humidity is 100%, at which time both readings are the same. The difference between the wet-bulb and dry-bulb readings, when applied to tables developed for that purpose, results in relative humidity and dewpoint temperature. The dewpoint is the temperature to which air must be cooled at constant pressure and constant water vapor content to reach saturation (100% relative humidity). When air is cooled to dewpoint temperature, small water droplets condense on objects and dew forms.

SLING PSYCHROMETER - A sling psychrometer sometimes is used to speed up the process of getting accurate wet- and dry-bulb readings. The sling psychrometer can be whirled around to rapidly bring the wet bulb into contact with a great volume of air. This contact with air accelerates the evaporation rate. The person using the sling psychrometer should face the wind and should shield the instrument as much
possible from the direct rays of the sun. Whirling should not be too rapid because it force might displace the mercury columns in the thermometers. The whirling should be repeated until no further change can be detected in the wet-bulb reading.
The dewpoint is computed by using the psychrometer table. For example, a dry-bulb temperature of 60 F and a wet-bulb temperature of 50.5 F. The difference between the two readings is 9.5 F. This difference is called the depression of the wet bulb.
To compute the dewpoint, enter the table with the wet-bulb reading (50.5 F). Read across the top of the table to the proper depression column (9.5 F). Read the dewpoint temperature (42 F) directly from the intersection of the temperature row and the depression column.


The men who "go down to the sea in ships" fight a continuous close action with the elements that make up the weather. To seafarers the state of the weather is more important than it is to most people ashore. Accurate weather forecasting may not be as vital now as it was in the days of sailing but situations still arise in which the safety of a ship and the lives of her crew depend on the action you take to avoid the full fury of a storm. Even when actual safety is not considered, possible damage to the ship, her gear, and the like, should be minimized by security measures taken well in advance of a approaching storm.

The atmosphere (air) is a mixture of independent gases. Near the surface of the Earth the percentages by volume are approximately 78% nitrogen, 21 % oxygen, 1 % argon, with traces of other gases such as carbon dioxide, hydrogen, neon, and helium. Water vapor, which is found in relatively small but widely varying amounts; 1% of the total atmosphere may be taken as the average. The quantity of water vapor present is much greater in equatorial regions than in polar regions, and greater over the ocean than over land. The atmosphere has definite weight, called atmospheric pressure, and it is measured by an instrument called a barometer.
Large-scale changes in temperature, pressure, and water vapor content of the air cause the changes in weather. Warm air is lighter in weight and can hold more water vapor than cold air. Moist air with a temperature of 50°F is lighter than drier air of the same temperature because water vapor is lighter than air. Cold or heavy air has a tendency to flow toward and supplant warm or lighter air, and as the air begins to move, other forces come into play, making the movement of air masses and weather complex. Temperature, humidity, and atmospheric pressure are all factors in considering the weather. You probably don't need to be told that a thermometer is an instrument for measuring temperature. It is a glass tube of small bore in which either alcohol or mercury expands and contracts with the rise and fall of the temperature of the surrounding medium.
Most thermometers are mercury-filled and practically all of them use the Fahrenheit (F) scale, in which the freezing point of water is 32° and its boiling point is 212°. Temperature in meteorology, sometimes is expressed according to the Celsius (C) (formerly Centigrade) scale, in which the freezing point of water is 0° and its boiling point is 100°.
You might be to convert a Fahrenheit reading to Celsius, or vice versa. If 32 F is equivalent to 0 C, to change a Fahrenheit reading to Celsius you first subtract 32° and then multiply the remainder by 5/9. Say you want to change 41°F to Celsius Subtracting 32° from 41 ° gives 9°. Multiply by 5/9, and you get 45/9, or 5°C. To change from Celsius to Fahrenheit just reverse the procedure. First multiply Celsius temperature by 9/5, then add 32.
A thermometer must be read properly to obtain an accurate result. First, if you handle it, be sure that you do not touch the lower part of the glass containing the alcohol or mercury, because the heat from your body can affect the height of the mercury or column. Make sure that the top column is level with your eyes; otherwise you will be reading a higher or lower graduation than the one actual one.



0 - under 1 kt Calm Sea like a mirror.

Beaufort Scale - Wind Speed - Effects Observed At Sea

1 - 1-3 kts Light Air - Ripples with appearance of scales, no foam crests.

2 - 4-6 kts Light Breeze - Small wavelets, crests of glassy appearance, not breaking.

3 - 7-10 kts Gentle Breeze - Large wavelets, crests begin to break, scattered whitecaps.
4 - 11-16 kts Moderate Breeze - . 5 - 1.25 meters high, becoming longer, numerous whitecaps.

5 - 17-21 kts Fresh Breeze - Moderate waves of 1.25 - 2.5 meters taking longer form, many whitecaps, some spray.

6 - 22-27 kts Strong Breeze - Larger waves 2.5 - 4 meters, forming whitecaps everywhere, more spray.

7 - 28-33 kts Near Gale - Sea heaps up, waves 4-6 meters, white foam from breaking waves begins to be blown in streaks.

8 - 34-40 kts Gale -Moderately high (4-6 meter) waves of greater length, edges of crests begin to break into spindrift, foam is blown in well marked streaks.

9 - 41-47 kts Strong Gale -High waves (6 meters) sea begins to roll, dense streaks of foam, spray may reduce visibility.

10 - 48-55 kts Storm - Very high waves (6-9 meters) with overhanging crests, sea takes a white appearance as foam is blown in very dense streaks rolling is heavy and visibility is reduced.

11 - 56-63 kts Violent Storm - Exceptionally high (9-14 meters) waves, sea covered with white foam patches,visibility stilI more reduced.

12 - 64 and over - Hurricane Air filled with foam waves over 14 meters, sea completely white with driving spray, visibility greatly reduced.


ESTIMATING THE WIND AT SEA - The master and mates on board ships at sea can deter­mine the speed of the wind by estimating its Beaufort Force. Through experience ships officers have various methods of estimating this force. The effect of the wind on the observer himself, the ship's rigging, flags, etc, is used as a criterion. Estimates on these give the relative wind which must be corrected for the motion of the ship before an estimate of the true wind speed can be found.

The most common method is the appearance of the sea surface. The state of the sea disturbance, the height of the waves, noticeing of white caps, foam or spray, depends on three factors.

1. The wind speed - The higher the speed of the wind, the greater is the sea desturbance.

2. The duration of the wind - At any point on the sea, the disturbance will increase the longer the wind blows at a given speed, until a maximum state of disturbance is reached.

3. The Fetch - This is the length of the stretch of water over which the wind acts on the sea surface from the same direction. For a given wind speed and duration, the longer the fetch, the greater is the sea disturbance. If the fetch is short, say a few miles a disturbance will be small no matter how great the wind speed is or how long it has been blowing.
There are other factors which can modify the appearance of the sea surface caused by wind alone. These are strong currents, shallow water, swell, precipitation, ice, and wind shifts.
A wind of a given Beaufort Force will produce a appear­ance of the sea surface provided that it has been blowing for a length of time, and over a long fetch. The effects of currents, shallow water, swell, precipita­tion, etc., should also be absent. The use of the sea criterion has the advantage that the speed of the ship need not be considered. The mariner observes the sea surface, noting the size of the waves, the white caps, etc., and then finds the criterion which describes the sea surface as he saw it. This criterion is associated with a Beaufort number, for a mean wind speed and range in knots are given. There are other factors besides the duration of the blow and the fetch that affect the appearance of the sea surface and these should be considered if they are present.


Galaxies - Their are number of nebulae that have been identified as extra­ galactic,
it has been discovered that these small cloudy patches are groups of stars, in many ways resembling the group of stars of which the sun is a part. Each of these stars constitutes an island universe as separated from others as individual stars in one group,this group is called a galaxy. In a galaxy the stars tend to be in groups,these are called star clouds, arranged in long spiral arms. The spiral nature is due to the revolution of the stars about the center of the galaxy. This is due to the inner ones revolving more rapidly than the outer ones.
Galaxies which have been discovered seem to congregate in groups, similar to stars in a galaxy. The average estimate of the size of a galaxy is that it is about 100,000 light years in diameter, 15,000 light years thick at the center, and 5,000 light years thick near the outer edge, and that it contains 100,000,000,000 stars.


Stars are really just distant suns, even the nearest star is too far to be seen as more than a point of light in the biggest telescope. The distance of the stars is so great that none is known to have a heliocentric parallax (difference in apparent position as observed from the earth and the sun) of as much as 1".
Stars are different in size from giants having diameters greater than that of the orbit of the earth, to small ones which may be no larger than the major planets. The size and density cover wide ranges. The color of stars vary with the temperature, a hot star is bluish-white, and a colder star, is a faint red. ln Orion, blue Rigel and red Betelgeuse, are located on opposite sides of the belt, and look noticeable different.
Under ideal viewing conditions, the dimmest star that can be seen with the unaided eye is of the sixth magnitude. In the entire sky there are about 6,000 stars of this magnitude or brighter. Half of these are below the horizon at, about 2,500 stars are visible to the unaided eye at any time. When looking for stars for a sight I have about 15 of the brighter ones that I use and keep track of where they are in the sky.

Stars which have a change of magnitude are called variable stars. A star which suddenly becomes several magnitudes brighter and then gradually fades is called a nova. A real bright one is called a supernova.
Two stars that look close together are called a double star,if more than two stars are included in the group, it is called a multiple star, and if a large number appear in a spherical shape, it is called a globular cluster. The Pleiades and some stars of the Big Dipper are examples of open clusters. A group of stars which appear close together, are called a constellation, particularly if the group forms a striking configuration. The ancient Greeks recognized 48 constellations covering only certain groups of stars. Today astronomers recognize 88 constellations.
Stars rotate on their axes, and revolve around the center of their galaxy, Motion of a star through space like any celestial body is called space motion. Stars are great for viewing during the winter because their are so many neat ones showing, you just have to have a clear night to enjoy them.



BOLD RED = One of the original constellations of Ptolemy

Leo Minor




Pisces Austrinus



Tringulum Australe

Ursa Major
Ursa Minor




BOLD RED = One of the original constellations of Ptolemy

Canes Venatici
Canis Major
Canis Minor
Canis Minoris


Coma Berenices
Corona Australis
Corona Borealis