$B 315 13S Isrsii^SSSeiSito: MALL BOAT NAVIGATION By F. W, STERIJNO loa #v .>^ ./.M:l ^M. . r I 9n ^1 P^;/^^ M ^ SMALL BOAT NAVIGATION SMALL BOAT NAVIGATION BY LIEUT. COM. F. W. STERONG U. S. NAVY (RETIRED) *♦»»••* » THE MACMILLAN COMPANY 1942 .'Si REPLACING COPTBIOHT, 1917, Bt the Macmillan company All rights reserved — no part of this book may be reproduced in any form without permission in writing from the publisher, except by a reviewer who wishes to quote brief passages in connection with a review written for inclusion in magazine or newspaper. ii*:r:--i*!:: : - TrifiUd in the United States of America by THK PEBBI8 PBINTmO COMPANY, NEW TOBK CONTENTS PART I NAVIGATION CHAPTER PAGE I Navigation ^ II Navigational Instruments, Books, Rec- ords, Etc 14 III The Vessel's Position 44 IV Dead Reckoning ....... 75 PART II SEAMANSHIP V Soundings, Tides, Etc 97 VI Light and Buoy System of the United States 110 VII Weather 118 VIII Rules op the Road 180 M168705 PART I NAVIGATION SMALL BOAT NAVIGATION CHAPTER I NAVIGATION NAVIGATION is that science which affords the knowledge necessary to conduct a ves- sel from one point to another on the earth and provides a means of determining the position of the vessel at any time. There are three gen- eral branches to this science, viz : (1) PHoting. (2) Dead Reckoning. (S) Nautical Astronomy, PUotmg is determining the position of a vessel by observations on known visible charted objects, or by soundings of the depth of the sea. Dead Reckoning, or the method of sailings, is a means of deducing a vessel's position from the direction and distance sailed from a previous known position. This method involves the rules of plane trigonometry. Nautical Astronomy treats of the determina- tion of a vessel's position by observation of celes- 9 Yd "SMALL BOAT NAVIGATION tial bodies — the sun, stars, moon, and planets. It is based on spherical trigonometry and its use is principally confined to deep sea navigation. On this account it is not dealt with in this work. UNITS DEFINED The Statute Mile, which is 5,280 feet, is em- ployed in land measurements. It is used to some extent in navigating river and lake vessels, espe- cially on the Great Lakes, but by far the more commonly used unit is The Geographical or Nautical Mile, This unit of linear measurement, used by navigators, is gen- erally termed the nautical or sea mile. It is ap- proximately 6,080 feet. It has various values as defined by the standards of different countries, but from the navigator's standpoint these various standards do not vary materially from the above value. Jt is equal to a minute of arc of the equa- tor, "^For purposes of navigation the nautical mile is assumed equal to a minute of latitude at all points of the earth. Hence, when a vessel changes her position to the north or south by one nautical mile, it is assumed that the latitude has changed 1'. Owing to the fact that the meridi- ans converge toward the poles, the difference in longitude due to a change of position of one mile to the east or west varies with the latitude. NAVIGATION ii Whereas a departure (change of position to east or west) of 1 mile at the equator equals 1' of arc, the same departure of 1 mile in a latitude of 60° amounts to 9f in longitude. The Knot is the measure of speed and equals one nautical mile per hour. The Axis of the Earth is a diameter passing through the poles of the .earth and about which the earth revolves. The Terrestrial Equator is a great circle of the earth passing through the middle point of this axis and perpendicular thereto. It divides the earth into the Northern and Southern hemi- spheres, and every point on this equator is equi- distant from the poles. Longitude is measured along the equator. Terrestrial Meridians are great circles of the earth passing through the poles. They are per- pendicular to the equator. Latitude is measured on the meridians, being 0° at the equator and 90° at the poles. The Meridian of a place is that meridian passing through the place. The Prime Meridian is that meridian from which longitude is measured. The meridian passing through Greenwich, England, is almost \^ universally accepted as the prime meridian for navigation. Longitude is measured from 0° at Greenwich, East and West to 180°. ^fj-t^'- 'V^' '', t> '^ ■:.fc o ^■< .^ 'J't 12 SMALL BOAT NAVIGATION Parallels af Latitude are small circles of the earth parallel to the equator. The Latitude of a place is the arc of the merid- ian intercepted between the equator and that place. It is reckoned north and south from the equator as an origin, up to 90° at the poles. The Longitude of a place is the arc of the equa- tor intercepted between the meridian of the place and the prime meridian. Longitude is measured East and West through 180° from the meridian of Greenwich. The Difference of Latitude of two places is the portion of a meridian included between the two parallels of latitude passing through the two places. When two places are on the same side of the equator the difference of latitude is the nu- merical difference between the latitudes of the places ; when on opposite sides of the equator the difference of latitude is the numerical sum of the two places. The difference of latitude is called North or South to indicate in which direction a vessel would sail to make the change. The Difference of Longitude of two places is the arc on the equator intercepted between the meridi- ans passing through the two places. When the places are in the same longitude (viz: East or West), the difference of longitude is the numer- ical difference between the longitudes of the two NAVIGATION 13 places ; when in different longitudes, the difference in longitude is the numerical sum of the two longi- tudes, or 360° minus this sum. The difference of longitude is marked East or West to denote in which direction a vessel would sail to make the change. CHAPTER II NAVIGATIONAL INSTRUMENTS, BOOKS, RECORDS, ETC. 1. NAVIGATIONAL INSTRUMENTS THE following instruments are indispensa- ble to the navigator when piloting: (a) di- viders or compasses, (b) parallel rulers, (c) log, chip or patent, (d) lead and line, (e) compass, liquid, dry, or gyroscopic, (f) azimuth circle, (g) barometer, mercurial or aneroid, (h) thermometer. A sextant and protractor may also be included in the outfit, although the former is entirely unnecessary, (a) Dividers (or Compasses) consist of two pointed legs movable about a joint so that the points at the extremities of the legs may be set at any desired distance apart. Dividers is an in- strument used for measuring distances on a chart. One of the pointed extremities can be replaced by a pencil or pen for describing arcs or circles and in this case the instrument is called a compass, (b) Parallel Rulers consist of two wooden straight edges, joined by two metal links, so con- 14 INSTRUMENTS, BOOKS, ETC. 15 structed that in all positions of the links the straight edges are always parallel to each other. It is used to draw lines parallel to each other, and especially in chart work for transferring lines on the chart to the compass rose, ,for laying off courses by transferring them from the compass rose, and for plotting bearings of objects. (c) The Log is an instrument for measuring or estimating the speed of the vessel and the dis- tance run for any given period. It takes a va- riety of forms that may be classified under two heads, the chip log (which measures the speed of the vessel at any instant) and the patent log (which is cumulative and measures the distance run for any interval). The Chip Log, which is quite inexpensive and can be made by the navigator, consists of three parts, the log-chip, the log-lme, and the log-glass. Its principle is that, if a light object is thrown from the ship, it ceases to partake of the motion of the ship as soon as it strikes the water. If after any known interval of time its distance from the ship is known (this being equivalent to the distance the ship has travelled in the known in- terval of time) the approximate speed of the ship can be computed. The log-chip is a thin wooden quadrant of about 5'' radius, the circular edge being weighted i6 SMALL BOAT NAVIGATION with lead so that the chip will float upright, apex up. The log-line is knotted into a hole at the apex. The ends of a bight of line are knotted into the other two corners of the chip. Into this bight is seized a wooden peg which fits into a Fig. 1.— Chip Log. «ocket seized on the log-line. When the peg is in the socket, all three lines to the corners of the chip are of equal length. This contrivance facilitates hauling in the chip after the speed is obtained. The log-line^ which is made of halyard stuff, is about 150 fathoms long. One end is secured to the chip and the other to a reel on which the line is wound. The line is marked at about 15 fath- oms from the chip end by a piece of bunting. This part of the line is called stray line. From this piece of bunting the line is marked at every 47 feet 3 inches by a piece of fish line held between the strands of the log-line, the line being marked by a knot in the fish line for every division (47 feet 3 inches) from the bunting. Thus at 94 feet INSTRUMENTS, BOOKS, ETC. 17 6 inches from the bunting the piece of fish line has two knots in it, etc. These main divisions, called knots, are further subdivided into five equal parts by pieces of white bunting , between the strands to indicate two-tenths of a knot. The log-glass is a sand glass similar to an hour glass constructed to run for 28. seconds. A 14j- second glass is also used. Three men are needed to " heave the log." One heaves the chip-log and tends the log-line, one holds the reel, and one tends the log-glass. To find the speed by the chip-log, hold the reel by its handles and unwind some of the stray line. Insert the toggle in its socket and heave the chip overboard, allowing the line to run out freely. As the first piece of bunting, which marks the end of the stray line, passes over the rail invert the log-glass. Just as the last particle of sand passes from the top to the bottom of the glass seize the log-line, which has been running out freely. The subdivisional mark which is now at the rail indi- cates the speed of the vessel in knots and tenths. For instance, if the cord having three knots is at the rail, the vessel is making three knots per hour. This can be demonstrated as follows : Principle of Construction, When the chip hits the water it ceases to partake of the motion of the ship and becomes stationary in the water. 1 8 SMALL BOAT NAVIGATION Between the first mark and the third the interval of time is 28 seconds (the time it takes the sand to run from the top to the bottom of the glass). In this interval of time the vessel moves 3 times 4*7 feet 3 inches (as shown by the log-line). Now in feet is the distance that the vessel would move in one hour at the same rate. ^ 3X47.25X60X60 ^^ Or = 3 knots per hour. 28 X 6080 The 28-second glass is used for low speeds. For speeds over 5 knots a 14-second glass is used and the reading of the log-line is doubled. To haul in the line after a reading is obtained, give the line a sharp tug. This will release the toggle and the chip will lay flat on the surface and can be hauled in hand over hand and reeled up. The whole apparatus should be overhauled fre- quently to check the log-line markings and the log- glass. The line must be frequently checked and remarked as it stretches or shrinks, and should be marked when wet. The glass is checked by comparing it with a watch, and the sand is dried if it becomes damp as indicated by requiring more than 28 seconds to pass from the top to the bot- tom of the glass. Figure 1 shows the parts of the chip-log and INSTRUMENTS, BOOKS, ETC. 19 the necessary dimensions for making one of these instruments. In lieu of the log glass furnished with commer- cial outfits time may be kept with the watch and for convenience a 30-second interval may be sub- stituted for the 28-second interval indicated by the log glass. In this case the knot marks on the log line are placed 50 feet 8 inches apart. The principle of marking the log line can be checked easily. Suppose the vessel is moving at the rate of one knot (6080 feet per hour). Then in 30 seconds it would move 50 feet 8 inches. This is the length between markings. If the line is accurately marked and the log properly con- structed the speed indicated by the chip log will be one knot. The Patent Log is a mechanical contrivance for measuring the actual distance that a vessel travels through the water. It is sometimes called a taff- rail log because it is usually installed on the taff- rail. It takes a variety of forms, but all are more or less subject to inaccuracies and all em- body the same principles. The patent log consists of three parts, (1) the rotator, a conical shaped piece of brass fitted with vanes which is towed astern and caused to rotate as it passes through the water at a speed propor- tionate to the speed of the vessel; (2) a register , 20 SMALL BOAT NAVIGATION located on the vessel's rail. This register is con- nected to the rotator by a line which communi- FiG. 2.— NegTis Taffrail Log. cates the revolutions of the rotator to cyclometer gear in the register. The whole is so calibrated INSTRUMENTS, BOOKS, ETC. 21 that the miles and tenths run by the vessel are reg- istered bj appropriate dials on the register; (3) the line, which is specially made. Usually about 400 feet of line is used to connect* the rotator and the register. A high speed requires a longer line than a low speed. The parts of the Negus Taffrail Log are shown in Figure 2. Patent logs are not exact instruments and many inaccuracies enter even when in good work- ing order. They must be carefully watched. If correct at one speed they may be inaccurate at a faster or slower speed; they register differently in a head and a following sea, and in smooth and rough weather. The error of the patent log should be determined for varying conditions of sea and at different speeds for every run between two ports, if the speed is not affected by tide, and a record of errors under these varying conditions should be kept to correct future readings. The revolutions of the screw propeller afford the most accurate measure of the speed of a vessel and the distance steamed. The revolutions of the propeller (engine speed) can be obtained by a small instrument called a tachometer. By run- ning over a measured mile (or other known dis- tance) at various engine speeds, the revolutions corresponding to various speeds can be obtained and tabulated thus : 22 SMALL BOAT NAVIGATION Revolutions Speed in Knots 85 7 97 8 110 9 125 10 142 11 160 12 etc. Entering this table with the average revolutions for any interval of time, the corresponding speed can be obtained. While this is the most accurate method of getting the speed, it must be borne in mind that by whatever of the above methods the speed is obtained, it is the speed through the water and that to obtain the speed made good over the ground allowances must be made for the local current. (d) The Lead and Line is a device for ascer- taining the depth of water. It consists of a suit- ably marked line, having a long hexagonal or oc- tagonal lead at its end. Two sizes of leads are used, one weighing from 7 to 14 pounds, called the hand lead, and used for depths up to 25 fathoms, and the other weighing from 30 to 100 pounds, called the deep sea lead, and used for depths over 25 fathoms. Lead lines are marked, measuring from the bot- tom of the lead secured to the line, as follows : INSTRUMENTS, BOOKS, ETC. 23 At 2 fathoms with two leather strips, 3 fathoms with three leather stripg, 5 fathoms with a white rag, 7 fathoms with a red rag, 10 fathoms with a leather having a hole in it, 13 fathoms the same as 3, 15 fathoms the same as 5, 17 fathoms the same as 7, 90 fathoms with two knots, 95 fathoms with one knot, 30 fathoms with three knots, 35 fathoms with one knot, etc. Sometimes the lead is marked in feet around the depth corresponding to the vessel's draft. Soundings that correspond to depths marked on the lead line are called " marks "; intermediate soundings are called " deeps,** Lead lines should be marked when wet, and should frequently be verified and remarked when necessary. The bot- tom of the deep sea lead is hollow. When taking a sounding this cavity is filled with tallow (called " arming the lead " ) which picks up a sample of the bottom. This allows a comparison with the character of the bottom as indicated on the chart. The Sounding Machine is an instrument for obtaining rapid soundings at great depth. It is employed on all large ships and is described at length in Chapter 6. (e) The Compass may take one of three forms, liquid, dry, or gyroscopic. The liquid compass is the one most commonly used in this 24 SMALL BOAT NAVIGATION country and will be described later. The dry com- pass is used extensively in England. The gyro- scopic compass is used in the U. S. Navy ; its high cost precludes its use in any but the largest ships. The Wet Compass consists of a skeleton card 7%" or less in diameter, made of tinned brass, rest- ing on a pivot in liquid, with provision for two pairs of magnets symmetrically placed. The mag- nets consist of four cylindrical bundles of steel wire that are magnetized as bundles between the poles of an electromagnet. They are cased in cylinders and secured to the underside of the com- pass card in a direction parallel to the North and South markings of the card. The card is curved, annular shape or flat, gradu- ated by quarter points, and a card circle is ad- justed to its outer edge graduated to half degrees, with readings at every point and every five de- grees, as seen in Figure 3. The card is secured on a concentric spheroidal air vessel which rests on liquid in the compass bowl. The air vessel is fitted with an agate bear- ing which rests on a pivot in the compass bowl, most of the weight of the card being supported by the liquid and only a slight pressure being on the pivot. The compass bowl of cast bronze has a glass cover so that the card can be seen. The cover is INSTRUMENTS, BOOKS, ETC. 25 made tight by a rubber gasket. The liquid in the bowl is 45% pure alcohol and 55% distilled water. The inside of the bowl is painted white and a lubber's point is drawn in the bowl in the Pio. 3. — Compass Points. fore and aft line of the ship. This is the refer- ence point when reading the compass. The under side of the bowl constitutes an ex- pansion chamber which allows for expansion with a change of temperature of the liquid in the bowl. 26 SMALL BOAT NAVIGATION The bowl is mounted by double gymbals on a com- position stand. This stand contains magnets to compensate the compass. The bowl can be cov- ered by a spun brass hood which fits on the stand and can be revolved for taking bearings. Boxing the Compass is the process of naming the points in their order. The four points, Fig. 4. — Azimuth Circle. North, East, South, and West, are called cardmal points. Midway between the cardinal points are the intercardinal points, N.E., S.E., S.W., N.W. The names of all points are shown in Figure 3. (f) The Azimuth Circle consists of a com- position ring which fits over the edge of the com- pass bowl, Figure 4*. At one extremity of a diam- eter is a curved mirror hinged to move about a horiiontal axis, and facing this, at the other ex- INSTRUMENTS, BOOKS, ETC. 27 tremity of the diameter, is a cased prism which has a narrow slit in the case facing the mirror. This part of the instrument is used to take azimuths of the sun for compass work. At the extremities of another diameter (at right angles to the first) is a hinged vertical wire, and a hinged plate having a vertical slit. This is used for taking direct bearings of an object. Hinged on the same pivot as the vertical wire is a smoked glass reflector for azimuth work with the sun or stars. A level on the azimuth rim shows when the circle is horizontal. All observations must be taken with a horizontal azimuth circle. (g) The Barometee is an instrument for measuring the atmospheric pressure. Barometric observations are necessary for weather predic- tions. Some form of barometer is necessary on all vessels. There are two forms, the Mercurial Ba- rometer, and the Aneroid Barometer. The mer- curial barometer is carried on large yachts. Smaller boats should be equipped with the aneroid. The Mercurial Barometer indicates atmospheric pressure by the height of a column of mercury. If a glass tube, closed at one end, is entirely filled with mercury and then placed open end down over a cup of mercury (no mercury being allowed to es- cape from the tube during the operation) the mer- 28 SMALL BOAT NAVIGATION cury in the tube will fall until its level is about 30 inches above the level of the mercury in the cup. This column of mercury, in the tube, is sustained by the pressure of air on the mercury in the cup, and will rise or fall with this pressure (which is atmospheric pressure). This is in effect a barometer. In practice the cup and tube are encased in a brass case, cut away near the level of mercury in the tube ; along this opening is a scale for reading the height of mercury in inches, a twrnier being fitted for ac- curate readings. The Vernier is an attachment used on many in- struments, such as barometers, sextants, protrac- tors, etc., to facilitate exact readings. It consists of a metal scale, similar in construction to that of the scale to which it is fitted and arranged to move along the main scale by a rack and pinion. The vernier scale has a total length equal to one of the whole divisions of the main scale, but this length is divided into one more or one less part than the number of subdivisions into which the whole division of the main scale is divided. Suppose that a barometer scale is divided into tenths of an inch and that a length of nine such divisions be divided into ten parts for a vernier, Figure 5. Number the vernier divisions from at the bottom to 10 at the top. If the bottom divi- INSTRUMENTS, BOOKS, ETC. 29 OP- ^7. ^-5a sion of the vernier is brought level with the top of the mercurial column the scale is read as follows: In Figure 5 the mercury stands above the mark 29.6 on the main scale. Find the division of the ver- nier that coincides with a division of the main scale. In the figure this division is " 1." Therefore .01 must be added and the exact read- ing is 29.61. The Aneroid Barometer is an in- strument by which the atmospheric pressure is measured bj the elastic- ity of a metal plate. It consists of a cylindrical brass box, the metal being very thin. This box is in a state of partial vacuum. As the atmospheric pressure increases the enclosed air is compressed and the ends of the box approach each other. Suitable levers communicate this motion of the box ends to a pointer that moves over a suitable scale. These levers magnify the motion of the box ends and the scale is cali- brated to indicate the air pressure. Barometer Comparisons. What- ever the form of barometer used, it * scale. -J19.S ^za 30 SMALL BOAT NAVIGATION will be subject to errors due to derangements or to inaccurate construction. Because of this it is necessary to compare the barometer frequently with a standard of known error. At all principal ports a standard mercurial barometer is available for comparison. From this comparison the ba- rometer error can be computed and applied to fu- ture readings. At the principal ports the reading of a standard barometer at specified times is pub- lished in the daily papers. By observing the ba- rometer on board at the same time the error of the vessel's instrument is obtained. (h) The Thermometer is an instrument for measuring temperatures. Its principle is too well known to require discussion. It is an aid to the mariner in predicting weather, judging the humid- ity of the atmosphere, and, through the tempera- ture of the sea water, finding proximity of cur- rents such as the Gulf Stream. Sea water used for observations should be drawn from at least three feet below the surface. The Psychrometer consists of two thermome- ters called the wet and dry hulhs. The dry-bulb thermometer gives the temperature of the air. The wet-bulb thermometer is exactly like the dry- bulb except that its mercurial bulb is surrounded with cloth which is kept moist. It indicates the temperature of evaporation. By reading both INSTRUMENTS, BOOKS, ETC, 31 bulbs the humidity of the air is obtained and prob- ability of rain can be foretold. The Sextant ^ is one of the most valuable of deep sea navigational instruments, but is of little Fio. 6.— Sextant use when coasting. It is used to obtain the angle between two objects, terrestrial or celestial, by bringing into coincidence at the observer's eye the rays of light from the two objects, one ray direct 1 Although the sextant is of little use for motor boats its description and method of adjustment is given here for general information. 32 SMALL BOAT NAVIGATION and the other ray by double reflection. Its gen- eral form is shown in Figure 6. The frame is of brass or other composition. The graduated arc (cc) is generally of silver, the graduations being by degrees and minutes, the smallest subdivision representing generally 10'. By means of the ver- nier (d) the instrument can be read to smaller divisions, usually 10'', 15", or 20". The magni- fying glass (g) facilitates reading the vernier. A wooden handle is fitted for holding the instru- ment. A brass index arm (o) carrying the ver- nier (d) is pivoted at the center of the arc (cc). It carries the index glass (a) which moves with the pivot of the index arm (o) as an axis. A second glass (b), called the horizon glass, is fixed to the frame. It is half mirror and half trans- parent, the line of demarcation being parallel to the plane of the instrument. Both glasses are perpendicular to the plane of the instrument and are provided with adjusting screws to permit of adjustment. The index arm can be clamped in position on the arc (cc) by the clamp (e) and the tangent screw (f) can give the arm small movements after it is clamped. A telescope (i), supported in an ad- justable ring on the frame, is used to give greater distinction to the images. In lieu of this tele- scope the star telescope (k) or plain sighting tube INSTRUMENTS, BOOKS, ETC, 33 (1) may be used. Colored shades (hh) are fitted before the index and horizon glasses to protect the eje from sun glare. The same result obtains by using the colored cap (n) on the telestope. The vernier (d) is constructed on the same prin- ciple as that explained under the barometer. To Use the Sextant for measuring angles pro-* ceed as follows : Point the telescope at the lower object, if one is above the other, or at the left hand object, if both are in nearly the same hori- zontal plane. Keep this object in direct view through the transparent part of the horizon glass, and move the index arm until the reflection of the second object is seen in the silvered part of the horizon glass. When the objects are nearly in coincidence, clamp the index arm and by the tan- gent screw bring the objects in exact coincidence at the line of demarcation on the horizon glass. The angle between the objects is now shown on the arc. When measuring the height of an object above the horizon the nearest point of the horizon, directly below the object must be employed. To find this point swing the instrument about the line of sight as a center, keeping the image of the ob- ject in the middle of the field. The object will appear to describe the arc of a circle, the lowest point of which marks the vertical. When bring- ing a celestial object doi^ to the horizon it is 34 SMALL BOAT NAVIGATION usual to set the instrument to zero and point it at the object. Then keeping the object in the field move the index arm until the horizon appears in the field. Adjustments of Sextant, The adjustments ordinarily made by the navigator are to keep the horizon and index glasses perpendicular to the plane of the instrument, and the line of sight par- allel to the plane of the instrument. Adjustment of the Index Mirror. Clamp the arm near the middle of the arc. Place the eye near the index mirror and sight along the plane of the instrument. If the direct and reflected im- ages of the arc appear in one plane the index mir- ror is in adjustment, perpendicular to the plane of the instrument. If the reflected image of the arc appears to droop from the direct image the glass leans backward; if it seems to rise the glass leans forward. Adjust by screws back of the mirror. Adjustment of the Horizon Mirror, Having adjusted the index mirror, select a celestial ob- ject, preferably a star, to adjust the horizon mir- ror. Put in the telescope and direct it toward a star. Move the index arm until the reflected im- age passes the direct image. If one passes di- rectly over the other the mirror is in adjustment. If one passes to one side of the other, adjust the INSTRUMENTS, BOOKS, ETC. 35 horizon mirror by its attached screws until the images pass one over the other. Adjustment of the Line of Sight is more diffi- cult. Screw the star telescope, which has two parallel wires in its eye piece, into the ring; turn the eye piece until the wires are parallel to the plane of the instrument. Select two well defined objects whose angle is greater than 90° (stars preferred). Bring these objects into coincidence at one wire of the eye piece. Now move the in- strument until they are seen at the other wire. If still in coincidence the line of sight is in adjust- ment. If not, correct by the adjusting screws of the ring. The Index Error of a sextant is an error in its reading due to the fact that when both mirrors are parallel the zero of the vernier does not co- incide with the zero of the arc. This error does not necessarily remain constant and it is good practice to determine it each time the instrument is used. The Index Correction, which is the index error with its algebraic sign reversed, is the correction that must be applied to an observed angle to get the true angle. It may be found by observation on (a) a star, (b) the sea horizon, (c) the sun. (a) Bring the direct and reflected images of the star into coincidence and read the sextant. 36 SMALL BOAT NAVIGATION This reading is the index correction, and is + ^^ — according as the vernier zero is to the right or left of the zero on the arc. (b) Proceed in a similar manner, substituting the sea horizon for the star. (c) Bring the upper limb of the direct image of the sun tangent to the reflected lower limb. Read the instrument and mark the reading + or — as in (a). Now bring the lower limb of the direct image tangent to the reflected upper limb. Read the instrument and give the proper alge- braic sign according to the above rule. One half the algebraic sum of the two readmgs is the index correction. Of these three methods the first is preferable as it is the most accurate. Always make contact by moving the tangent screw in the same direction. The Koch Protractor is one of the most use- ful instruments known to piloting. It combines all the facilities of a portable compass rose, the parallel rulers, the protractor, and the plotter. It is described at length in the next chapter. g. BOOKS AND ACCESSORIES (a) Charts. A full set of coast and harbop charts should be on hand for all waters that it is intended to visit, or that any emergency might cause the owner to visit. Before sailing care must INSTRUMENTS, BOOKS, ETC. 37 be taken to see that these charts are corrected to date. A weekly bulletin issued by the U. S. Hy- drographic Office, Washington, D. C, supplies all corrections and can be had on request. An un- corrected chart is not infrequently the cause of grounding. Large scale harbor charts should be obtained for all harbors and inland waters that may be visited. The following various publications, issued by the Hydrographic Office, dealing with special fea- tures of navigation, should be regularly consulted. They can be found at any branch Hydrographic Office in the large sea ports. Pilot Charts of the various oceans, which fur- nish information about drifting derelicts, ice and floating obstructions, storm tracks, average wind and weather, ocean currents, etc. Hydrographic Btdletin, weekly, which gives weekly changes of the above. DaUy Memorandum, which gives daily informa- tion of interest to mariners. Notices to Mariners, which are weekly bulletins of changes in aids to navigation (lights, buoys, etc), dangers to navigation (rocks, shoals, bars, etc.), and in general all facts that affect charts, sailing directions, etc. All charts and sailing di- rections should be kept corrected to date from these notices. 38 SMALL BOAT NAVIGATION (b) A Light and Buoy List of latest date must be carried. It consists of a list of lights and buoys with their location (Latitude and Longi- tude), their descriptions and characteristics, and other information such as fog signal stations and submarine signal stations. It can be obtained from the Hydrographic Office and must be kept corrected to date in a similar manner to, and from the same source as, the charts. (c) Sailing Dikections of that part of the world to be navigated should be carried. They come in bound volumes, each volume covering a large tract of pilot waters. They give detailed information of harbors, coasts, currents, courses for entering harbors, cable, provision and coaling facilities, in fact are indispensable fonts of navi- gational data. They are obtained from the same source as the charts and are corrected from the same publications. For American waters use U. S. Coast Pilots. (d) Bowditch's Useful Tables (latest date) should be used. This book contains 48 dif- ferent tables, and these comprise all the tables needed for any coasting or piloting problem that may arise. (e) Tide Tables and the Nautical Ephemeris of the current year may be carried but are not necessary while on pilot waters. The Nautical INSTRUMENTS, BOOKS, ETC. 39 Ephemeris will be needed if any celestial observa- tions are made, and in this case a well rated chro- nometer will also be necessary. The time of high and low water for any port may be obtained from the local paper. ~ 3. RECORDS THAT SHOULD BE KEPT (a) The Log Book is a record of the vessel's cruise, and is a most necessary accessory. It should contain aU the data of the navigation by dead reckoning, and should afford a complete me- teorological record. In addition all occurrences of note should be recorded. It is the only available legal record in case of crime or accident on board. Hourly data. The following hourly data should be entered in the log at the end of each hour. 1. Knots, to nearest tenths, made good during the hour. 2. Patent log reading, if one is carried. 3. The average engine revolutions for the hour. 4. Courses steered during the hour. (The exact time of changing course, with the patent log reading at that time should be recorded. This data is used to work up the dead reckoning, which is discussed later.) 6. The wind, its force and direction. 6. The barometer, and its attached thermometer. 7. The thermometer, both wet and dry bulb. 8. The temperature of the sea water. 9. State of weather. 10. Clouds, form, quantity, and direction from which moving. 11. State of sea. 40 SMALL BOAT NAVIGATION The information in 1, 2, 3, and 4 is used for navigation. The information in 5, 6, 7, 9, 10, and 11 is used to foretell the weather. (8) The temperature of the sea water will help detect the proximity of ice, or the presence of a cold or hot current, such as the Gulf Stream. The Force of the Wmd (5) is recorded numer- ically from (a calm) to 12 (a hurricane). Ad- miral Beaufort devised a convenient scale which is given in part below: Force of Wind. Velocity in Statute Miles 'per Hour. — Calm 0-3 1 — Light air 8 2 — Light breeze 13 3 — Gentle breeze 18 4 — Moderate breeze 23 5 — Fresh breeze 28 6 — Strong breeze 34 7 — Moderate gale 40 8 — Fresh gale 48 9 — Strong gale 56 10 — Whole gale 65 11 — Storm 75 12 — Hurricane 90 and over. The State of the Weather (9) is entered in the log by symbols as follows : INSTRUMENTS, BOOKS, ETC. 41 b — Clear blue sky. p — Passing rain showers, c — Clouds present in sky. q — Squally weather. d — Drizzling. r — Continuous rain, f — Foggy. s — Snow falling. g — Gloomy, stormy look- t — Thunder.. ing. u — Ugly or threatening fa — Hail. , weather. 1 — Lightning. v — Variable weather, m — Misty. w — Heavy dew. o — Overcast sky. z — Hazy weather. Clouds. In the scale for the amount of clouds, represents a clear cloudless sky and 10 a sky entirely overcast. The amount of clouds is re- corded in tenths of the sky covered by them. The following are the principal forms of clouds, given in order of their altitude above the earth, begin- ning with the most elevated. 1. Cirrus (Ci.) — Detached delicate, fibrous looking clouds, in the form of feathers, generally white, sometimes arranged in belts converging toward one or two points of the horizon. 2. Cirro-stratus (Ci.-S.) — A thin whitish sheet or a tangled web formation. The sheet formation sometimes causes halos around the sun or moon. 3. Cirro-Cumulus (Ci.-Cu.) — Small globular masses or white flakes, having no shadows, or very light ones, arranged in groups or lines. 4. Alto-Cumulus (A.-Cu.) — Large globular whitish or grayish masses, partially shaded, arranged in groups or belts. 6. Alto-Stratus (A.-S.) — A thick sheet of grayish or bluish color, showing a brilliant patch in the neighborhood of the sun or moon, but does not produce halos. This form of cloud is similar to the Cirro-Stratus but is only about half as high. 42 SMALL BOAT NAVIGATION 6. Strato-Ctimulus (S.-Cu.) — Large globular masses or rolls of dark cloud, frequently covering the whole sky, especially in winter. It differs in appearance from the nim- bus in this globular or rolled appearance, and does not bring rain. 7. Nimhvs (N.) — Rain clouds; a thick layer of dark clouds without shape and having ragged edges. Through the opening in these clouds an upper layer of Cirro-Stratus or Alto-Stratus may almost invariably be seen. Loose clouds visible floating at a low level under a Nimbus sheet are Fracto-Nimbus (Fr.-N.), called by sailors "scud" 8. Cumulus (Cu.) — Wool-pack clouds; thick clouds of which the upper surface is dome-shaped and exhibits pro- tuberances, while the base is horizontal. The true Cumu- lus has clear superior and inferior limits. It is often broken up by strong winds, and the detached portion is called Fracto-Cumulus (Fr.-Cu). 9. Cumulo-Nimbus (Cu.-N.) — The thunder-cloud or shower-cloud; heavy masses of clouds in the form of tur- rets, mountains, or anvils, generally having a fibrous sheet above, and Nimbus beneath. From the base are generally seen showers descending. 10. Stratus (S.) — A horizontal sheet of lifted fog; when broken up by wind it is called Fracto-Stratu* (Fr.-S.). The State of the Sea is recorded by the follow- ing symbols: B — Broken or irregular sea. M — Moderate sea or swell. C — Chopping, short or cross R — Rough sea, G — Ground swell. S — Smooth sea. H — Heavy sea. T — Tide rips. L — Long rolling sea. (b) The Navigator's Note Book. The navigator should keep a note book in which to enter all the bearings and observations taken, and INSTRUMENTS, BOOKS, ETC. 43 all work and calculations connected therewith. It should form a complete history of all navigation performed, 4. REPORTS MADE Anything of an unusual nature should be re- ported to the Hydrographic Office at Washing- ton; derelicts sighted, icebergs, any buoy or marker that is suspected to be out of position, any light that is out or that is not showing in accord- ance with its latest description in the Light List, any unusual meteorological phenomenon, in fact anything that will promote safe navigation, should be reported. Every mariner should have the best interests of the brotherhood at heart. All navigational information in this country emanates from the Hydrographic Office and it is entitled to the aid of every person who performs navigation. CHAPTER ni THE vessel's position THE bearing of an object from a ves- sel is the direction in which the object is seen from the vessel. It is the angle be- tween the meridian passing through the observer and the object. It is called true, magnetic, or compass, depending upon the meridian of refer- ence chosen. This is explained later. A Line of Position is any line on which the vessel's position is known to be, that can be plotted on a chart. A Line of Bearing is any line of position ob- tained from a bearing. A Position Point is any point on either a line of position or a line of bearing at which the ves- sel's position is known to be. A position point, generally called a " ^," can be obtained by the intersection of two lines of position, two lines of bearings, or one of each. COMPASS ERROR Variation of the Compass. Since the earth's magnetic pole in each hemisphere differs in geo- THE VESSEL'S POSITION 45 graphical position from the geographical pK)le, the earth's magnetism will cause the compass nee- dle to point to a spot (the magnetic pole) that is different from the geographical pole' (called the true pole). Hence the compass needle will point at an angle to the true meridian. The geograph- ical pole lies true North of all points in the North- ern hemisphere. The angle that the great circle through the observer's position and the magnetic pole makes with the true meridian (viz: the great circle through the geographical pole) is called the variation. This variation differs for different points on the earth. The variation for any given locality is shown on the charts. A nautical chart always contains the data from which the navigator can find the variation for any locality for any year. Deviation of the Compass. In addition to the variation, the compass ordinarily has a still further error in its reading. This arises from the effect produced on it by masses of magnetic metal in the vessel itself. Deviation, which is produced by attraction of the compass needle by magnetic iron within the vessel itself, varies for different vessels, different headings of the same vessel, and undergoes change as a vessel proceeds from one geographical locality to anothen A 46 SMALL BOAT NAVIGATION table compiled to show the deviation on all head- ings is called a deviation table. The Compass Error is the algebraic sum of the variation and deviation. As stated before the variation can be obtained from a chart. The de- viation is obtained from a deviation table which is constructed by " swinging ship." This and the operation of " compensating the compass " are beyond the scope of the average amateur, but in all ports are mariners who make a specialty of this work. The simplest method of " swinging ship " for deviation, that by ranges, is described on page 49. From what has gone before it is seen that there are three methods by which bearings and courses may be expressed: (1) true, when referred to the geographical, or true, meridian; (2) magnetic, when referred to the magnetic meridian; and (3), compass, when referred to the meridian in which the compass needle lies. To convert compass bearings or courses to mag- netic bearings or courses it is necessary to apply the deviation, corresponding to the vessel's head- ing, to the compass bearings or courses. Likewise to convert magnetic hearings to true hearings the variation for the locality must be applied to the magnetic bearings. The process of applying variation, deviation, THE VESSEL'S POSITION 47 and compass error under all circumstances is one with which the navigator must become thoroughly familiar; these various problems are constantly arising; no bearing can be plotted, orr course ac- curately set, without involving this problem, and careful study of this subject is recommended. When the effect of a compass error, whether arising from variation or deviation, is to draw the North end of the compass needle to the right the Fio. 7. — Compass Error. Fio. 8. error is named East or is marked + ? when its ef- fect is to draw the North end of the needle to the left it is named West, or marked — . Figures 7 and 8 represent, respectively, exam- ples of Easterly and Westerly errors. In both figures consider that the circles represent the ob- server's horizon, N. and S. being the true North and South points in each case. If N.' and S.' rep- resent the corresponding points indicated by a 48 SMALL BOAT NAVIGATION compass whose needle is deflected by a compass error, then in Fig. 7, the North end of the nee- dle being drawn to the right the error is Easterly or plus, and in Fig. 8, the North end of the needle being drawn to the left the error is Westerly or minus. Considering Fig. 7, if we assume the Easterly error to be one point, it is apparent that, if a di- rection N. by W. is indicated by the compass, the true direction is N., or one point to the right. Similarly, if the compass direction is N. by E., the true direction is N.N.E., or still one point to the right. If we follow around the whole compass card, the same relation will still hold in every case, the true direction being always one point to the right of the compass direction. Thus, if the com- pass direction is South, the true direction is S. by W. To understand this consider that you stand in the center of the compass card facing in the direction of the compass reading. In Fig. 8, assuming the compass error to be one point Westerly, the converse of the above holds true. All true directions are one point to the left of the corresponding compass directions. Thus, if the compass direction is N. by E., the true di- rection will be North. A few simple rules should be remembered when working compass problems: THE VESSEL'S POSITION 49 1. When the true bearing is to the right of the compass bearing the error is East, 2. When the true bearing is to the left the error is West, 8. When applying the compass error imagine yourself standing in the center of the compass card, facing the direction involved in the problem. 4. Deviation plus variation equals compass error. This means the algebraic sum: thus, if variation is 5° E. ( + ), and deviation is 3° W. ( — ), compass error is 2° E. ( + ). 5. To convert from compass to magnetic direc- tion, if the magnetic direction is to the right, the deviation is Easterly. Conversely, to convert a compass direction to a magnetic direction, if the deviation is Easterly, apply it to the right of the compass bearing, if Westerly to the left. 6. To convert from magnetic to true directions, apply the variation to the right of the magnetic direction if the variation is Easterly, and to the left if Westerly. Swinging Ship foe Deviation. Variation for any locality can be obtained from the chart of that locality. To find the compass error on any ves- sel heading it is necessary to know the deviation on that heading. The simplest way of determining the deviation on the various compass headings of a Tessel is to swing ship by the method of ranges. 50 SMALL BOAT NAVIGATION A Range consists of two well defined and charted objects in line with each other. The di- rection of the line through these two objects can be ascertained from the chart. Ranges whose magnetic bearings are known have been formed naturally or have been laid out for the aid of navi- gation in nearly all localities. To obtain the deviation on various compass headings of a vessel (a deviation table) proceed as follows: Having located a magnetic range, steam across this range on various compass head- ings (every compass point if time and circum- stances permit). Steady on the course for three minutes before crossing the range. Observe the compass bearings (on each heading) of the range when the two objects are in line as observed from the vessel. The deviation for each heading is the difference between the compass bearing of the range on that heading and the known magnetic bearing of the range. Rule. — The deviation is Easterly when the magnetic hearing is to the right of the compass bearing, and Westerly when the magnetic bearing is to the left of the compass hearing. An example will serve to clear up the above: Suppose the magnetic bearing of the range is N.E. (N.45°E.). Steaming across the range the compass bearing on each point of compass THE VESSEL'S POSITION 51 heading ^ is taken as follows (columns 1 and 8): Column 1 Compass Heading Column 2 Compass Bearing of Range Bearing of Range Column 3 Magnetic Column 4 Deviation N N \r E N 45° E 2 W N by E N 48** E >» 3 W NNE N 49° E » 4 W NE by N N ^r E >» 9 W NE N 45'' E >j NE by E N 43° E >» 2 E EXE N 42° E » 3 E E by N N 41° E n 4 E Record in column 3 the magnetic bearing of the range. To obtain column 4« take the numerical differences between columns 2 and 3 and mark the results East or West according to the rule given above. Before Stomgmg Ship see that all portable metal objects, especially those near the compass, are secured in the positions habitually occupied by them at sea. A change in the position of metal objects near the compass will affect its deviation. See that the vessel is on an even keel. This rule also applies when taking bearings. Steam across the course slowly, having enough headway to keep a steady course. » Only eight compass points arc taken for demonstration. 52 SMALL BOAT NAVIGATION The navigator should swing ship when practical before any long trip, or after laying in port any very long interval. It is not necessary to obtain the deviation on every compass point. If a table of deviations on every other point is constructed the deviation on intermediate points can be inter- polated. THE VESSEL'S POSITION Finding the Vessel's Position, when piloting, resolves itself into four general cases: 1. To get the vessel's position when one object of known position is in sight. % To get the vessel's position when two objects of known position are in sight. 3. To get the vessel's position when more than two objects of known position are in sight. 4. To get the vessel's position when no objects of known position are in sight. Case 4 is a method of soundings and as such is discussed in Chapter 5 under that heading. (1) To Get the Vessel's Position When One Object of Known Position Is in Sight. (a) By hearing and distance. Take a com- pass bearing of the object. Convert this bearing to magnetic or true bearing by applying deviation or compass error. Plot this line of bearing on the chart by means of parallel rulers, using the mag- THE VESSEL'S POSITION 53 netic or true compass rose, depending upon whether the bearing has been converted to a mag- netic or true bearing. The vessel lies somewhere on this line. If the distance from the object can be obtained, an arc of this length with the object as a center will intersect the line of bearing at the vessel's position. The distance may be estimated, but this is of doubtful value. An estimated distance may be verified by a sounding, if the bottom is very irregu- lar so that a characteristic sounding may be ob- tained. The distance from an object may be found by the vertical angle method if the height of the ob- ject is known, and the angle the object subtelids at the observer can be measured. The heights of all lighthouses are given in the Light List. Meas- ure the angle subtended by the lighthouse by means of a sextant. Now h d=:.567 — O where 4 = » 15 + 1% n 40 + 3% yy 48.5 + 8% » 5 Lat 10 P.M. ..Sa**— 10.2'N Long 10 p.m. .75**— 33.2'W Day's Run. It is customary to calculate the total run for the preceding 24 hours every day 92 SMALL BOAT NAVIGATION as V N E W (Bearing of Lightship) 82° 8 1.1 7.9 110° —5° —6° —11° 99° 6 0.9 5.9 84° —5° —4° — 9° 75° 8 2.1 7.7 79° —5° —4° — 9° 70° 10 3.4 9.4 67.° —5° —3° — 8° 59° 15 7.7 12.9 20° —6° +1° — 5° 15° 40 38.6 10.4 ^6° — 6° + 3° — 3° 283° 48.5 10.9 47.2 240° — 7° +8° -f- 1** 241° 5 2.4 4.4 (Current) 48° 7 4.7 5.2 68.5 3.3 65.2N 3.3 59.4 51.6 = DL 7.8E 51.6 = Dep at noon. Having the vessel's positions at two succeeding noons the problem resolves itself into finding the course and distance made good be- tween the two positions. Example. The position of a vessel at noon of July 12, 1914, is Lat 35°— lO'N, Long 134°— Ol'W, on July 13, 1914, the vessel's position is Lat 36°— 03'N, Long 131°— 14' W. Find the course and distance made good. Pos. July 13....36°— 03'N 131°— U'W Pos. July 12....35°— lO'N 134°— Ol'W Run 53'N ..D Lo 2°— 47'E = 167'E Middle Lat = 36° approximately, D Lo = 167'. From Table 2, Dep = 135.1. Entering Table 2 with Lat 53 (which is D L above), and Dep = 135.1, we obtain Course OSVi* Distance 146 miles, made good. DEAD RECKONING 93 Graphic Soltttion op Dead Reckoning. A much quicker solution of a vessel's run by dead reckoning can be made graphically on the chart. From the point of departure draw the true course on the chart. Measure from the point of de- parture the distance run on this course. From this second point draw the second course on the chart and lay oflP from this second point the dis- tance run on the second course. By continuing this process the vessel's position by dead reckon- ing at any instant can be obtained. This affords an excellent check to the computations. PART II SEAMANSHIP CHAPTER V SOUNDINGS, TIDES, ETC. APPROACHING LAND SOUNDINGS are taken for two general pur- poses : first, when in shallow water, to ascer- tain that there is sufficient depth of water for the immediate movement of the ship, and to check the depths as given on the chart ; second, to verify dead reckoning positions when on soundings in a fog or when land is not in sight. The best aids to navigation, when running in a fog, are the sounding machine and the hand lead, and the navigator should make every possible use of them. Even in clear weather the sounding ma- chine, or deep sea lead in lieu thereof, may be of great aid to the navigator in verifying h» posi- tion. This is especially true when making a land- fall. The lead and line, and the deep sea lead and line are described in Chapter 2. The Sounding Machine.^ This machine pos- 1 Whereas, a Sounding Machine will only be found on a large yacht navigated by a licensed Master, it is still con- sidered of sufficient importance to merit a short description. 97 98 SMALL BOAT NAVIGATION sesses advantages over the deep sea lead, for which it is a substitute, in that soundings can be obtained at great depths and with accuracy and rapidity without stopping the ship. It consists of a stand on which is mounted a reel which holds the sounding wire. Crank handles are fitted to the reel for reeling in the wire after a sounding has been taken, and a suitable brake controls the reel when the wire is running out to take a sound- ing. The lead is secured to the outer end of the wire. Its base is hollow to receive tallow for arm- ing. Attached to the sounding wire, just above the lead, is the depth registering instrument en- closed in a hollow cylindrical case. Various reg- istering devices are in use, but all depend upon the increasing pressure of water at increasing depth. The Lord Kelvin Machine employs, for its reg- istering device, a slender glass tube, sealed at one end and open at the other. This is coated inside with a chemical preparation which changes color on contact with sea water. This tube is placed, closed end up, in the metal container. When tak- ing a sounding, as the lead sinks, taking the regis- tering device with it, the air contained in the glass tube is compressed with a force dependent upon the depth. Salt water enters the open end as the air is compressed, and this makes a clearly de- SOUNDINGS, TIDES, ETC, 99 fined line of discoloration a distance from the open end dependent on the depth. A scale is provided upon which the depth can be measured by this mark of discoloration. Ground glass tubes may be substituted for the chemically prepared ones. When a ground glass tube is wet, it shows clear over the wetted surface. Such tubes can be used an indefinite number of times, if thoroughly dried each time. Mechanical depth recorders can be substituted for the glass tubes. In such a device water pres- sure acts upon a piston against the pressure of a graduated spring, and the depth is recorded on a scale by an index pointer that is moved by the piston. When Making Land in a Fog the sounding ma- chine, or deep sea lead, must be kept going at half hour intervals for some hours before it is expected that soundings can be obtained. Several sound- ings at irregular intervals are worse than useless as they give no definite information and may lead to disaster. In using the sounding machine, be careful not to invert the tube when withdrawing it from the tube case, as that would cause water to run toward the closed end of the tube, causing a discoloration and hence a false reading. The lead must be freshly armed at each cast. Having picked up the bottom, the navigator can proceed 100 SMALL BOAT NAVIGATION as described under ** Piloting by Soundings in a Fog," Keep a sharp lookout for any landmarks that may appear during a momentary lifting of the fog, and listen carefully for signals. If a fag signal is heard, the landmark where it is situated can be determined by reference to the Light List, which gives the characteristics of all fog signals (viz: the number and duration of the blasts). If approaching land and the soundings indicate a dangerous proximity to land, if no signals have been heard that will further aid navigation, the only safe course is to anchor or stand off shore. When running slowly in a fog (as the law re- quires) it must be borne in mind that the relative effect of current is increased. Sometimes, when approaching a bold bluff shore, a vessel may be warned of its proximity by having its own fog sigj nals echoed back from the cliff. In some inland waters where cliffs are frequent, navigators de- pend upon this to a great extent. Piloting by Soundings in a Fog. Soundings taken in a fog serve a much more important func- tion than merely to give the depth of water at any one position. The vessel's position can often be found by a series of soundings. In thick weather, when approaching or running close to land, or in inland waters, soundings should be taken contimi- so UNDINGS, TIDES, EtO: ibi ously and at regular intervals, and the character of bottom should be noted. By laying off the soundings on tracing paper along a line that rep- resents the track of the ship and to d scale (dis- tances between soundings) corresponding to the scale of the chart and then moving the tracing paper on the chart so that the courses plotted are parallel to corresponding directions on the chart until the observed soundings agree with the chart soundings, the vessel's position can generally be well determined. While some waters by the quick changes in soundings along the bottom adapt themselves more readily than others to this method, there are few places where the navigator cannot at least keep out of danger by these indi- cations. When the navigator can no longer de- termine with some degree of accuracy that his course leads clear of danger, it is time to anchor until more favorable conditions present themselves. To illustrate the above by a simple example: Suppose the vessel is making 12 knots over the ground, and that she has steered East for 30 min- utes and then NE for 30 minutes. Suppose that soundings have been taken at five minute intervals as follows: 6, 7, 8, 7, 12, 8, 10 (when course was changed), 9, 7, 6, 8, 6, 10, fathoms. On tracing paper lay off, as in Figure 21, to the scale of the chart, AB = 6 miles, BC = 6 miles (30 minute I02 SMALL BOAT NAVIGATION runs at 12 knots), and ABC = 135° (angle be- tween courses). This represents the track of the vessel. Now divide AB and BC each into 6 equal parts. These are one mile intervals and the divi- sion points represent the positions at which the soundings were taken. Mark the soundings at the proper division points, and move the tracing pa- -^A./-l Fig. 91. — Piloting by Soundings. per over the chart, always keeping the line AB in the East and West line of the chart. At some portion of the chart it will be found that the depths on the tracing paper correspond to depths on the chart (if the soundings have been carefully taken) and the vessel's position is at the point of the last sounding. Orienting the tracing paper is facilitated by drawing a few meridians, K, L, M, N, thereon. If SOUNDINGS, TIDES, ETC. 103 there is much range to the tide the stage of the tide must be noted when soundings are taken and allowance must be made for the height of tide. The soundings on the chart are for mean low water. Effect of Wind and Barometee on Sound- ings. When navigating waters where the depth exceeds the vessel's draft by only a small amount, it must be borne in mind that a strong wind or unusually high barometer may cause the water at low tide to fall below the depth indicated on the chart. Piloting Among Coral Reefs. When pilot- ing among coral reefs or banks, a time should be chosen when the sun is astern. Conning should be done from an elevated position forward. When the observer is high up, the line of demarcation be- tween a reef or shoal and deep water is very clearly seen. When passing between shoals or dangers where there are no well charted navigational marks a mid-channel course should be steered. Too much emphasis cannot be laid upon this point. Do not save seconds by passing close to a danger when a safe course offers. Steering a mid-channel course by eye is a simple matter, as the eye can make a close estimate in a case of this kind. 104 SMALL BOAT NAVIGATION TIDES To an observer tides present themselves in two different manners, by alternate elevation and de- pression of the water level, and by alternate in- flows and outflows of streams. Properly speaking tides should refer to the vertical motion and tidal currents to the horizontal flows. However, popu- lar usage ascribes both these meanings to tides. When the water has reached a maximum level it is called high tide, or high water. When it has reached a minimum level it is called low tide, or low water. The interval at high and low water, when there is no perceptible movement, is called the stand. Between low and high water, when the tide is setting from the sea toward the land, the horizon- tal movement is called flood tide. When the hori- zontal movement sets from the land toward the sea, between high and low water, it is called ehh tide. The interval of change between flood and ebb, when there is no perceptible horizontal move- ment, is called the slack. The Cause of the Tides is the difl^erence in the attraction of the moon (and to a less degree of the sun) upon the various unit masses of water and the attraction of the moon on the earth itself. This diff^erence of attraction combined with the SOUNDINGS, TIDES, ETC. 105 relative periodic movements of the moon and earth produce the periodic ocean disturbances known as tidal phenomena. Establishment, The moon being the dominant factor in tide production, it is apparent that the phenomena should bear some relation to the lunar month (28 days). High and low water occur, on the average of these 28 days, at about the same intervals after the transit of the moon over the meridian. These nearly constant intervals, ex- pressed in hours and minutes, are known re- spectively as the high water lunitidal interval and the low water lunitidal interval. The in- terval between the moon's meridian passage at any place and the time of the next succeeding high water, as observed on the days when the moon is at full and change (new), is called the establish' ment; it is also spoken of as the time of high water on full and change days (abbreviated " H. W. F. & C"), for since the moon's meridian passage on these days occurs at midnight and noon (of the lunar day), the establishment is approximately the time of high water. If to the time of high water we add or subtract 6 hours 31 minutes (1/4 of a lunar day) the result will be the time of low water. Range, Spring and Neap Tides, The range of a tide is the difference in height between high and io6 SMALL BOAT NAVIGATION low water. At new and full moon the sun and moon produce high tides at the same times. The effect of the sun augments that of the moon and the resultant high tides are higher than the aver- age. Similarly the low tides are lower than the average, and the range of tides is greater. Tides at this season are called spring tides. At the time of first and third quarters of the moon the high tides due to the moon occur simultaneously with the low tides due to the sun. The resultant high and low tides are less than the average and the range is at its minimum. Tides occurring at this season are called neap tides. Tidal currents (flood and ehh) are strongest at spring tides and weakest at neap tides. Tidal Currents. It must be remembered that the periods of -flood and ehh in any locality are not necessarily coincident with the periods of rise and fall of the tide. The inward set of the sur- face current does not always cease when the water has attained its maximum height. Local condi- tions may be such that flood may continue after high water has been reached, or vice versa. This may be more apparent by comparing two tidal basins, one having a large open entrance and the other having a narrow restricted opening. In the first case the process of filling and emptying the basin keeps pace with the outside sea level and SOUNDINGS, TIDES, ETC. 107 ebb and fall, flood and rise, occur at practically the same time. In the second case the restricted entrance retards filling the basin so that the height of water without may reach a maximum long be- fore the basin fills. In this case flood contmues, possibly hours, after high water occurs, and in a like manner the restriction will cause ebb to con- tinue long after low water has occurred outside. Times of High and Low Water, The simplest and quickest method of obtaining the times of high and low water and other tidal data is by use of a Tide Table. One is published by the U. S. Coast and Geodetic Survey annually, and gives the times of high and low water at many seaports. From these others may be deduced. Much other tidal data is given in this publication. The daily pa- pers of many marine ports give the times of the tides for several days ahead of the date of issue. When no tidal table or data is obtainable the time of high water can be computed by use of the Nautical Almanac as follows : To the time of the moon's meridian passage add the lunitidal interval (H. W. F. & C), obtained from the chart or from Bowditch's Useful Tables. The time of the moon's meridian passage is ob- tained as follows: From the Nautical Almanac pick out the Greenwich Mean Time of the Upper Transit of the Moon at Greenwich for the local io8 SMALL BOAT NAVIGATION date (Page IV). Also pick out the daily varia- tion on the same line. With this 'variation and with the Longitude as arguments enter table 11, Bowditch, and obtain the correction to be applied to the G. M. T. of Greenwich Transit. The result is the Local Mean Time of the moon's meridian passage. Now add to this the time of H. W. F. k C. and the result is the Local Mean Time of high water. This can be converted to Standard time by applying the difference in time between the lon- gitude of the place and the Standard Meridian. Appendix IV, Bowditch, contains the mean luni- tidal interval of high and low water for many places. The charts give the establishments of many ports with sufficient accuracy for this work. General, To sum up, when approaching land or harbor, the navigator must know the draft of the vessel. He must make himself familiar with every detail of the charts he will use, and must form a mental picture of the land and aids to navi- gation that he will sight. Allowance must be made for the effect of the position of the sun or moon on the appearance of objects sighted. He must be familiar with the characteristics of all lights, buoys, fog signals, and other aids to navi- gation that he will use, and with the state of the tide and currents in channels he will navigate. He should select beforehand the objects that he will SOUNDINGS, TIDES, ETC. 109 use for bearings. He should carefully check all buoys to prevent confusion. Ranges should be selected and lines drawn to indicate safe courses and danger bearings where possible. The track of a vessel entering port should be laid down on a chart before entering, and this should be carefully inspected to see that it leads clear of all possible danger. The vessel's position must be frequently plotted on the chart and should never be in doubt for an instant. Soundings should always be taken when on soundings, whether the weather be clear or cloudy. The navigator should familiarize himself with the Inland Rules of the Road given in Chap- ter 8 before entering pilot waters. CHAPTER VI MGHT AND BUOY SYSTEM OF THE UNITED STATES LIGHTS LIGHTS are distributed along the coast, at harbor entrances, in harbors, and at other points to aid navigation. They may be placed in lighthouses, on lightships, or on buoys. When in lighthouses, there is generally one light to a house; when on lightships there is generally more than one. Lights are classified as fixed, flashing, intermit- tent, revolving, and fixed and flashing. This is necessary so that when a light is sighted it can be identified. It is obvious that if all lights were the same, the navigator might become confused when approaching land if his position were at all un- certain. A Fixed Light is one that shows uninterrupt- edly at all times. A Flashing Light is one that shows a short flash and is then occulted for a long interval. An Intermittent Light is one that shows a long flash and is occulted for a period shorter than the flash. 110 LIGHT AND BUOY SYSTEM iii A Revolving Light is one that gradually in- creases in intensity, then gradually decreases in intensity until it is occulted, and then gradually increases again. A Fixed and Flashing Light is a combination of the first two. Lights may be red or white in color. As stated before, the lights are given different characteris- tics so that they may be readily distinguishable. Flashing lights sometimes flash a number for this purpose. Generally speaking, main coast lights are white, although there are exceptions to this rule. Harbor lights may be white or red. Red lights are used to mark dangers, such as ends of breakwaters, etc. Red Sectors, Many white lights have red sec- tors, that is, the light shows white over part of the horizon, and red over other parts. Red sectors are used to mark dangers. In this case the light shows white as long as the observer is in safe navi- gable waters, but when in the same sector as a shoal or other danger the light shows red. In this case the vessel is safe as long as it is in the white sector. Light Lists, The United States is divided into a number of lighthouse districts. A list of lights is published by the Hydrographic Office for each district, and is sent on request to any ship cap* 112 SMALL BOAT NAVIGATION tain. These lists include all authorized lights, with their description, etc. Lights in lighthouses are described in the light lists as follows: (An example is taken from a list.) " Lighthouse color, white ; foundation brown ; lantern yellow. (This is to identify it by day.) " Hexagonal screw-pile structure ; light 44 feet above high water. " Bearings. (Here its bearings from other well charted objects are given.) " Character, 3000 candlepower, red, visible 8^ miles (for a height of eye of 15 feet above the sea level). " Fog Signal. (Here a description of the fog signal installed at the light is given.)" Light Vessels are moored at sea outside of im- portant harbors, and on the edge of important shoals on the coast where it is impracticable to plant lighthouses. They are described in the same light list. The names of the light vessels are painted on their sides. These names are taken from the shoal that the light guards, or from other sources. Numbers are often used in lieu of names. The description of a light vessel from the light list is given as follows : " Description, white ; masts yellow ; topmast and day marks black. LIGHT AND BUOY SYSTEM 113 **Rig. 2 masts, schooner rigged, oval day marks at each mast head. " Bearings. (Here follow the bearings of the light from well charted objects.) " Fog Signal, on whistle, blast of 3 seconds, si- lent 60 seconds, blast of S seconds, silent 60 sec- onds, etc. "If the whistle is out of order the signal is made on the bell as follows: 3 strokes, silent 60 seconds, 3 strokes, silent 60 seconds, etc." Light Buoys are used to mark the entrance to harbors, to guard shoals, and to mark the main channel of large harbors. They may be fixed or flashing, and red or white; all light buoys are de- scribed in the light lists. BUOYS All buoys, together with their location, are de- scribed in the light and buoy list of each district. Certain rules govern buoys which, if remembered, make navigation by buoys a simple matter. The particular feature about a buoy is its color. All buoys of each marked channel are numbered from seaward. Red buoys have even numbers and must be left on the starboard hand when entering harbor. Black buoys have odd numbers and must be left on the port hand when entering harbor. 114 SMALL BOAT NAVIGATION When a channel has two entrances from seaward local rules must govern. Thus on the Maine coast where chan- nels have two sea entrances buoys in thoroughfares and passages are numbered and colored for entering from East- ward. Buoys painted with red and black horizontal stripes mark shoals or other dangers, and should be given a wide berth. Channel buoys are fre- quently anchored abreast of these to mark the channel. Buoys painted with white and black vertical stripes are midchannel buoys and should be passed close to. Yellow buoys mark quarantine anchorages. White buoys mark anchorages. Shapes of Btwys. Buoys are shaped as fol- lows : Can, cylindrical. Nun, a truncated cone, or Spar. With the exception of spar buoys, all buoys are made of sheet iron, with water tight compart- ments to prevent sinking in case of damage. Where there is more than one channel in a har- bor the different buoys are used to mark different channels; nun buoys mark the main channel, can buoys, the secondary channels, and spar buoys, minor channels. When there is but one channel, nun buoys are placed on the starboard side and LIGHT AND BUOY SYSTEM 115 can buoys on the port (when entering from sea- ward). Buoys that mark important shoals on the coast are marked with letters or numbers ; {hus the buoy that marks the Frying Pan Shoal has F,P. painted on it. Bell buoys, whistling buoys, and buoys with balls, baskets, and other shapes mounted on a perch, mark turning points in the channel. The color and number of the buoy indicates on which side to pass. Where there is much ice, bell and gas buoys are frequently removed in winter, leav- ing only the spar buoy marking the position. FOG SIGNALS Fog Signals are established at all important lighthouses and light vessels to aid navigation in a fog. Each lighthouse and light vessel has a distinguishing signal so that it can be identified, and full descriptions of these are given in the light lists. The signal may be given on the whistle or beU. CHART NOMENCLATURE Lights are indicated on some charts by a yellow spot surrounding a black dot in the case of a white light, and a red dot in the case of a red light. Its characteristics, color, and range of visibility are marked on the chart abreast of it. ii6 SMALL BOAT NAVIGATION Buoys are marked on the chart with their num- bers and the following abbreviations to indicate their characteristics: B — black. R — red. H.S. — black and red, horizontal stripeB. V.S. — black and white, vertical stripes. C — can. N — nun. S — spar. The Character of the Sea Bottom is indicated as follows : one letter abbreviations are used to in- dicate kind of bottom, two letters to indicate color of bottom, and three letters for other qualifica- tions, as follows: M — mud. Yl — yellow. Brk — broken. G — gravel. Gy — gray. Sml — small. Soundings are indicated in fathoms unless oth- erwise noted. On harbor charts (^io>ooo scale) sounding will probably soon be changed to feet. Thus, 50 on the chart means 50 fathoms at mean low water, — means, *'no bottom at 50 fath- oms." 50 MiscelUmeous Maries, Other common indica- tions on a chart are: LIGHT AND BUOY SYSTEM 117 Rock awash at low water Rock, sunken Danger of doubtful existence (marked abreast) E.D. Danger of doubtful position (marked abreast) P.D. Anchorage, large vessels ^tJ Anchorage, small vessels "T* Wreck Xf ^ or -ffl- Lightship ibI ■■■» Currents are marked by an arrow, with two barbs for flood, and one barb for ebb ; the number on the arrow indicates the strength in knots. If the current is tidal, one, two, or three cross bars indicate the 1st, 2d, or 3d quarter of the flow. Thus si^^\ m indicates flood current in the 1st quarter, strength 3 knots per hour. Likewise 5»iL(^ indicates ebb current in the 3d quarter, strength 5 knots. CHAPTER VII WEATHER WINDS CAUSES of Winds. Wind is air In hori- zontal motion. It is defined by its direc- tion and force. The direction of the wind is the point of the compass from which it proceeds. Its force is generally measured by the Beaufort Scale described in Chapter II and de- pends upon its velocity. If air is warmer in one place than in an adjacent place, the warm air will rise and will be replaced by air flowing in from the second place. This creates a wind from the sec- ond to the first place. To take another view of the matter, in the warmer place the barometric pressure is lower than in the second (cooler) local- ity where the air is descending. The direction of winds is always from a place of high barometer to one of lower pressure. The Weather Bureau supplies data from which daily weather charts are plotted, showing the distribu- tion of barometric pressures over the United States and its adjacent waters. These charts 2i8 WEATHER 119 can be consulted in any large seaport. Weather predictions made from these charts are invaluable to the mariner. The greater the barometric range' between two adjacent places, the more violent the disturbance accompanying the transfer of air from the region of high barometer (called a "high") to the re- gion of lower pressure (called a "low"). When suflSciently violent we have a gale or storm. Ascending currents of warm air carry moisture that has evaporated from the sea. As the air as- cends it encounters lower temperatures which con- dense the moisture. If this moist air ascends to a sufficient height, or having ascended moves to a colder region, the moisture in the air is suffi- ciently cooled to be precipitated and we have the phenomenon of rain. Land and Sea Breezes. Generally speaking, the land is warmer than the adjacent sea by day, and cooler at night. This is due to the fact that the land as a whole absorbs and radiates heat more rapidly than will a large body of water; this is especially the case in summer. As a consequence of the above, a variation of pressure between the land and sea is established, which, though small, nevertheless is sufficient to affect the local winds. Under normal conditions, the wind blows from the sea toward the land dur- 120 SMALL BOAT NAVIGATION ing the day, and from the land toward the sea at night. Trade Winds. In the general terrestrial dis- tribution of the atmosphere the equator is belted by a region of low pressures. To the North and South of this belt are other belts of high pressure along the latitudes of approximately 30° North and South. Consequently, winds blow rather con- stantly toward the equator over a considerable area. Due to the effect of the earth's rotation these winds are from the Northeast in the North- em hemisphere and from the Southeast in the Southern hemisphere. These prevailing winds in the low latitudes are called the trades. The Doldrums. In the equatorial belt of low pressures there is little horizontal motion to the atmosphere. The atmosphere is slowly rising and the winds are stagnant, blowing fitfully in light airs from first one and then another point of the compass. Due to the constant evaporation and ascending air currents the weather is generally cloudy, with frequent thunder storms. This re- gion is called the Doldrums, The Horse Latitudes. The belt of high ba- rometric pressures that lies along latitudes in the Thirties, North and South, is another region of comparative calms. Here the breezes are also light, but the weather is clear in contrast with that WEATHER 121 of the doldrums. The reason lies in the fact that over this region a downward current of air pre- vails. This region is called the Horse Latitudes: BAD WEATHER Bad Weathee is a comparative term. A heavy squall that would be considered bad for a very small boat would not inconvenience a large vessel. For this reason an attempt has been made to classify bad weather in an unscientific manner that will be intelligible to the lay mind. No amount of rain or snow would endanger the safety of even a small boat. The factor in weather that must be considered is Wind, Al- though inconvenient and uncomfortable, rain will not affect the placidity of the sea; the condition of the sea depends upon the strength of the wind, and the safety of a vessel depends upon the strength and direction of the wind and the state of the sea. For the benefit of navigators of boats and small Tessels, bad weather might be classified as follows : (1) squalls; (2) gales; and (3) storms. This classification depends upon the strength and dura- tion of the bad weather. Squalls are of short duration, the wind is variable and a good sailor is safe in almost any small boat. Gales are of longer duration, the wind is stronger and steadier. 122 SMALL BOAT NAVIGATION and the seas are higher. Storms are often of sev- eral days' duration, the wind follows certain laws, being of cyclonic origin, and the seas become so high as to be dangerous to any but good sized ves- sels. Squalls may be encountered in almost any lo- cality. At some seasons they are of daily occur- rence in the tropics. There is little previous warning before a squall breaks, although a long period of squally weather will generally be pre- ceded by a falling barometer. A squall may or may not be accompanied by rain. When accom- panied by rain the warning comes as a grayish vertical curtain (the rain) obscuring part of the horizon. When this curtain is to windward the squall will probably strike the observer. When to leeward it may or may not be encountered. Often squalls work to windward. If a squall does not contain rain, the first indication is local agitation of the surface of the water. Wind on the water can be seen for a considerable distance. Squalls are accompanied by capricious shifts of wind of a puffy nature. The wind speed will rarely ex- ceed 35 miles an hour. Handling the Boat, Very small boats under sail should get the sail off before the squall strikes, as the uncertainty of the wind shifts might embar- rass. Any well handled boat is safe in a squall. WEATHER 123 If the sea becomes so high as to be uncomfortable on the course steered, run with the sea astern. If there is danger of the sea breaking over the stem, round to and lay head to the sea. The head may be kept up to the sea by putting a drag over the bow. A drag may be made by lashing to- gether a few oars, a spar and sail, or anything that will lie on or near the surface. Gales may be encountered in almost every local- ity. In our own waters they may be found in the Gulf of Mexico, along the entire Atlantic and Pa- cific sea coasts, and in the Atlantic along paths North of 30° Lat. and South of 25° Lat. The ba- rometer gives early indications of a gale. A stead- ily falling barometer, accompanied by a steadily increasing wind indicates the approach of a gale. A dull lowering sky. Nimbus clouds or " scud," with Alto-stratus or Cirro-stratus above, and a rising sea, all precede a gale. A red sky in the morning and halos around the moon or sun may be early indications. Gales are generally accompanied by rain, hail, sleet, or snow. The wind varies from 40 to 60 miles per hour. As the wind increases in intensity the barometer falls rapidly. These two conditions taken together are almost certain signs of a gale. Handling the Boat. Small boats should seek ihelter. Sail should be doused on sailing craft. 124 SMALL BOAT NAVIGATION Small craft will do well to run with the sea aft, with just enough speed on to keep the sea from breaking over the stem. If for any reason it is impossible to run this way and it becomes neces- sary to lay to, do so with the sea ahead, with a good drag over the bow. If necessary to lie hove to in fair sized craft it may be found that the ves- sel is more comfortable if hove to stern to the sea without a drag. Large vessels can generally pur- sue their course through a gale, but the speed should be reduced as the gale strengthens. Storms are invariably of cyclonic origin and follow well established rules in their movements and wind shifts. It is beyond the scope of this work to discuss the whole subject, but a few indi- cations of their approach and rules for handling vessels in a storm will be given. The duration of a storm may be several days, and during this en- tire period the wind blows at 75 miles per hour or more. It gradually shifts in direction according to well established rules given hereafter. Indica- tions of its approach are available for at least 24 hours before the storm breaks in all its fury. Early Indications. A storm is preceded by an abnormal rise of the barometer, with cool, dry, fresh winds and a cessation or reversal of the ordi- nary land and sea breezes. The atmosphere be- comes very transparent. A long low swell is pres- WEATHER 125 ent at a great distance from the storm center, sometimes several hundred miles, and this is occasionally accompanied by hurricane rollers. When there is no intervening island or land to di- vert them, the direction of the rollers indicates the direction of the storm center. Feathery Cir- rus clouds form on the horizon and radiate from a point on the horizon, which point also indicates the direction of the storm center. Unmistakable Signs, As the storm develops and comes nearer the sky becomes hazy and is cov- ered by a veil of Cirrus clouds which form halos by day and night. The barometer falls very rap- idly and becomes unsteady. The air is heavy, hot, and moist and the sky assumes red and violet tints at dawn and sunset. A low solid hurricane cloud bank forms on the horizon having the appearance of land. Squalls break off and diverge from this cloud bank and later these squalls pass the line of center of the bank. Fine misty rain forms with a heavy cross sea. As the storm develops the wind rises and the barometer falls more rapidly and becomes more unsteady. The wind blows at more than 90 miles per hour. Location of Storm Center, During the early observations the location of the storm center can be found by the directions of the rollers or of the storm bank as given above. As the storm devel- 126 SMALL BOAT NAVIGATION Ops and these can no longer be observed, the direc- tion of the center can be taken as 10 to 12 compass points from the direction of the wind, to the right m the Northern hemisphere and to the left in the Southern hemisphere. As the storm increases in intensity and the center approaches, after the barometer has fallen as much as one-half inch, the direction of the center may be taken at 8 points from the direction of the wind. Wind Shifts, In the Northern hemisphere the wind rotates around the storm center in an anti- clockwise direction. To an observer on a vessel if the wind appears to shift to the right, the ves- sel is in the dangerous zone of the storm; if the wind appears to shift to the left the vessel is in the navigable zone ; if the wind blows steadily from one direction as it increases in intensity, the vessel is in the path of the storm center. Handling the Boat, Small craft must seek shelter on the approach of a storm. Only large vessels are safe in them. There is apparently no limit to the degree of intensity of the wind, and the seas become very high and irregular. If forced to lie to this may be done with a drag, but a safer way is to run before the storm at just sufficient speed to keep the seas from breaking over the quarter. The following table shows the maneu- vers for sailing vessels caught in a storm: WEATHER 127 IN THE NORTHERN HEMISPHERE Heavb to oh the Starboabd Tack to Observe the Wiotj Wind Zone If the wind hauls The vessel is in Rim close hauled to the right the right or dan- on the starboard geroiis zone tack If obliged to lie to do so on the starboard tack. If the wind hauls The vessel is in Run with the wind to the left the left or nav- on the star- igable zone board quarter If obliged to lie to do so on the port tack If the wind re- The vessel is in Get the wind on mains steadj the path of the the starboard storm center quarter and keep that compass course If obliged to lie to do so on tack that the wind and sea will draw aft Large, full powered vessels will do well in the dangerous zone to run with the wind ahead or on the starboard bow as long as possible. This will work the vessel away from the storm center. The speed must be reduced, in fact just make steerage way. When it is no longer practicable to run into the seas lie to or run with the wind on the 128 SMALL BOAT NAVIGATION starboard quarter with just sufficient speed to keep the seas from breaking aboard. When in the left or navigable zone, run with the wind on the starboard quarter at a reduced speed. Lie to when necessary. If the vessel is in the track of the storm center get the wind on the star- board quarter, note the compass course, and keep this course until the vessel has worked its way out of the storm. Tornadoes and Water Spouts. A tornado might be likened to a concentrated storm, al- though this would not be technically correct. It depends upon an unstable and very humid state of the atmosphere, and is cyclonic in nature. A tor- nado may only be a few hundred yards in diame- ter. During an unstable and very humid state of the atmosphere, a warm, moist air current, stronger than usual forces its way up, and once started, increases in violence. The upward velocity and velocity of gyration are extremely high, the former reaching as much as 150 miles per hour, and the latter as much as SOO miles per hour. As the diameter is very small the vortex is very steep, and the barometer may fall from the normal to nearly zero, a state of per- fect vacuum. This accounts for the great dam- age done by this class of storm, the inside pressure of a building being normal and the outside pres- WEATHER 129 sure being nearly zero, the tendency is for the building to burst. This class of storm, due to its causes of formation, is always accompanied by rain around its outside. There is no rain in its center, the upward tendency of the atmosphere preventing the moisture from descending. A Water Spout is simply a tornado formed at sea in atmosphere laden with moisture where the dew point stratum is comparatively near the earth's surface. It is an erroneous belief that the water column is formed by water sucked up from the sea. This is not a fact. The water column is due to moisture drawn down from the heavy mois- ture-laden atmosphere. It is doubtful whether water is drawn up from the sea to any great ex- tent, and it is certain that the sea surface is not drawn up more than 30 feet, the height of the water barometer. CHAPTER Vni RULES OF THE KOAD SHIPPING, both on the high seas and in pilot waters, is bound by certain rules as to the lights to be carried, navigational signals to be made, and the manner in which to maneuver to avoid collision. International Rules of the Road govern these matters on the high seas and they are enforced by Maritime Law. They are agreed to by the prin- cipal nations and are promulgated by the legisla- tive bodies thereof. These rules always apply when on the high seas or in waters not under the territorial jurisdiction of any particular nation. Inland Rules of the Road. Rules for the con- duct of vessels in the territorial waters of differ- ent countries are promulgated by the legislative bodies thereof. Those promulgated by the U. S. Congress are similar in many respects to the Inter- national Rules. Important differences therein are pointed out in this chapter. These rules are not applicable to vessels on the Great Lakes, where a special set of rules govern. I3D X3X 132 SMALL BOAT NAVIGATION These rules apply to all vessels plying the in- land waters of the United States ; the limits of these waters are shown in Figure 22. All waters inside the dotted lines shown in this Figure are considered U. S. Inland waters for navigation. The rules are too voluminous to quote vn toto so a summary of the important ones follows: INLAND RULES OF THE ROAD Classification of Vessel. Any vessel pro- pelled fez/ machinery is classed as a steamer. Steamers when under sail and not under steam are classed as sailing vessels. In this case they must carry, by day, a black ball or shape forward to distinguish them from steamers under way. A vessel is considered underway when she is not at anchor, or made fast to the shore or aground. Lights of Vessels. All lights that are re- quired by the rules of the road must he shown from sumset to su/nrise, in all weathers, and during such time no other lights that may be mistaken for the prescribed lights shall be exhibited. 1. Steamier Lights When Underway, (a) Forward, a white light, visible at least 5 miles over an arc of 20 points of the horizon, from ahead to 2 points abaft both beams. This is known as the masthead light, (b) On the starboard side, a green light, visi- RULES OF THE ROAD 133 ble at least 2 miles over an arc of 10 points, from ahead to 2 points abaft the starboard beam. This is known as the starboard side light, (c) On the port side, a red light, visible at least 2 miles over an arc of 10 points, from ahead to 2 points abaft the port beam. This is known as the port side light, (d) An additional light similar to that de- scribed in (a) shall be carried aft and higher than (a). This additional light forms, with the mast- head light, range lights. (e) The green and red lights must have in- board screens so placed as to prevent them show- ing across the bow. These lights are carried lower than the masthead light. The additional light described in (d), which with the masthead light forms a range, is compul- sory in Inland Waters, except in the case of sea- going vessels and ferry boats. The International Rules make this light optional outside Inland Wa- ters. It is apparent that when a vessel on an even keel, carrying range lights, is seen head on, the lights are seen one above the other; if the vessel changes course the lights will open out, the lower one away from the upper one in the direction to which the vessel's head is changing. Such change gives instant notice of change of course and is 134 SMALL BOAT NAVIGATION more reliable than side lights because the distance at which the range lights can be seen is so much greater. Care should be exercised not to confuse range lights with towing lights, given under 2 (a). 2. Special Steajmee Lights, (a) When tow- ing, a steamer carries its regular lights and an additional light similar to the masthead light in a vertical line therewith, and, if towing more than one vessel and the tow exceeds 600 feet, it carries two such additional lights. These lights must be carried at least 3 feet apart. International Rules require that outside of in- land waters towing lights must be at least 6 feet apart. Care must be taken not to confuse towing lights with range lights. When range lights and towing lights are both carried, four lights in a vertical line may be seen. At distances beyond four miles 2 lights 6 feet apart blend into one. (b) Pilot Vessels when on their station shall carry forward a white light visible all round the horizon and shall exhibit a flare-up light at short intervals not to exceed 15 minutes. On the near approach to or of other vessels they shall flash their side lights at short intervals to indicate their heading. In addition to the above special lights required by the Inland Rules, the International Rules require the follow- ing lights, outside inland waters: RULES OF THE ROAD 135 (c) A Vessel Not Under Command carries for- ward two red lights in a vertical line one over the other, visible all round the horizon at least 2 miles. In the daytime it carries two black balls or shapes. (d) A Vessel Engaged in Laying or Picking Up a Cable carries forward three lights in a vertical line. The highest and lowest lights are red and the middle light is white. All are visible all round the horizon at least 2 miles. (e) When making way through the water Towing Steamers, Cable Vessels, and Vessels Not Under Command must carry side lights as pre- scribed for steamers. 3. Sailing Vessel Lights. A sailing vessel or a vessel being towed must carry the side lights pre- scribed for steamers but must not carry a mast- head light. 4. Small Steamers, Sail Vessels, and Row Boats, (a) Steam vessels of less than J^O tons carry a masthead light visible 2 miles and side lights visible 1 mile, but in lieu of side lights m>ay carry a combined lantern showing a green and red light from right ahead to 9. points abaft the beam on their respective sides. This lantern is carried at least 3 feet below the masthead light. (b) Rowing Boats, whether under oars or sail, shall have ready at hand a white lantern which 136 SMALL BOAT NAVIGATION shall be temporarily exhibited in time to prevent collision. 5. Lights for an Overtaken Vessel. A ves- sel which is being overtaken shall show from her stern a white light or flare up light to the over- taking vessel. 6. Anchor Lights.^ (a) A vessel under 150 feet in length shall carry forward at a height not over 20 feet a white light visible all round the hori- zon at least 1 mile. (b) A vessel of 150 feet or over shall carry forward at a height between 20 and 40 feet a white light visible all round at least 1 mile. At the stem she shall carry a similar light at least 15 feet lower than the forward light. In addition to the above the International rules prescribe : (c) A Vessel Agrownd in or near a fairway shall carry anchor lights as above and in addition the two red lights prescribed in 2 (c). No pro- vision is made for vessels aground in the Inland Rules and they carry the regular anchor lights. 7. Lights for Ferry Boats are prescribed by special rules established by the Supervising In- spector General of Steam Vessels and approved by the Secretary of Commerce. iNo distinction is made between steamers and sailing vessels in anchor lights. RULES OF THE ROAD 137 8. Rafts and Other Watee Ceaft not specif- ically provided for, navigating by hand power, horse power, or by the current of £^ river shall carry one or more good white lights in such man- ner as is provided by the Board of Supervising Inspectors of Steam Vessels. SOUND SIGNALS Sound Signals foe Passing Steamees. A Short Blast is one of about one second duration. When steamers are in sight of one another change of course is indicated by the following sig- nals: (a) One short blast means "I am directing my course to starboard." (b) Two short blasts means " I am directing my course to port." (c) Three short blasts means " My engines are going full speed astern." Sound Signals foe Fog. Fog signals ar« given by steamers on the whistle or siren. Fog signals are given by sailing vessels and ves-» sels being towed on the fog horn. A Prolonged Blast means one of 4 to 6 minutes' duration. 1. Fog signals must always be made by all vesi sels in fog, mist, falling snow, or heavy rain storm, whether by day or night. 138 SMALL BOAT NAVIGATION 2. Steam Vessels Underway, A steam vessel underway shall sound at intervals of not more than one minute, a prolonged blast. The International Rules differ materially from the above and are quoted here for use on the high seas: (a) A steam vessel having way upon her shall sound, at intervals of not more than 2 minutes, a prolonged blast. (b) A steam vessel underway, hut stopped^ and having no way upon her, shall sound at in- tervals of not more than 2 minutes, two prolonged blasts, with an interval of about one second be- tween. The navigator must hold clearly in his mind the fact that the " sound signals in a fog " must be used at all times in inclement weather, up to the moment of sighting another vessel. When two vessels come in sight of each other then " sound signals for passing vessels " should be used. It is a common error among seamen to use passing sig- nals when two vessels are within sound hut not sight of each other. This practice cannot be too severely condemned. 3. Sailing Vessels Underway shall sound at in- tervals of not more than 1 minute, when on the starboard tack, one blast ; when on the port tack, RULES OF THE ROAD 139 two blasts; when with the wind abaft the beam, three blasts in succession. 4. Vessels at Anchor shall, at intervals of not more than one minute, ring the bell rapidly for about 6 seconds. 6. A Vessel When Towing or being towed shall sound at intervals of not more than 2 minutes, three blasts in succession, namely: One pro- longed blast followed by two short ones. The International Rules prescribe this same signal for vessels employed in laying or picking up a cable and for vessels underway but not under command. 6. Rafts and other small craft not specifically provided for navigating by hand power, horse power, or by the current of a river, shall sound a blast of the fog horn or equivalent signal, at in- tervals of not more than one minute. SPEED IN A FOG Every vessel shall, in a fog, mist, falling snow, or heavy rain storms, go at a moderate speed, hav- ing careful regard to the existing circumstances and conditions. A steam vessel hearing, apparently forward of her beam, the fog signal of a vessel the position of which is not ascertained shall, so far as the cir- I40 SMALL BOAT NAVIGATION cumstances of the case admit, stop her engines, and then navigate with caution until danger of collision is over. What constitutes moderate speed in a fog is a much mooted question. However, it can be de- fined as such speed as will with certainty prevent collision. Clearly speed that might be permissi- ble on the high seas would be too high for crowded inland waters. It might even be necessary to stop and anchor in some cases. STEERING AND SAILING RULES 1. Preliminary. Risk of collision can, when circumstances permit, be ascertained by carefully watching the compass bearing of an approaching vessel. // the hearing does not appreciably change^ such risk should be deemed to exist. % Sailing Vessels. When two sailing vessels are approaching each other, so as to involve risk of collision, one of them will keep out of the way of the other, as follows : (a) A vessel which is running free shall keep out of the way of a vessel which is closehauled. (b) A vessel which is closehauled on the port tack shall keep out of the way of a vessel which is closehauled on the starboard tack. (c) When both are running free, with the wind on different sides, the vessel which has the RULES OF THE ROAD 141 wind on the port side shall keep out of the way of the other. (d) When both are running free, with the wind on the same side, the vessel which is to wind- ward shall keep out of the way of the vessel which is to leeward. (e) A vessel which has the wind aft shall keep out of the way of the other vessel. 3. Steam Vessels. When steam vessels are approaching each other head and head, that is end on, or nearly so, it shall be the duty of each to pass on the port side of the other ; and either ves- sel shall give, as a signal of her intention, one short and distinct blast of her whistle, which the other vessel shall answer promptly by a similar blast of her whistle, and thereupon such vessels pass upon the port side of each other. But if the courses of such vessels are so far on the star- board of each other as not to be considered as meeting head and head, either vessel shall imme- diately give two short and distinct blasts of her whistle, which the other vessel shall answer promptly by two similar blasts of her whistle, and they shall pass on the starboard side of each other. The foregoing only applies to cases where ves- sels are meeting end on, or nearly end on, in such a manner as to involve risk of collision; in other 142 SMALL BOAT NAVIGATION words, to cases in which, by day, each vessel sees the masts of the other in line, or nearly in line, with her own, and by night to cases in which each vessel is in such a position as to see both the side lights of the other. It does not apply by day to cases in which a ves- sel sees another ahead crossing her own course, or by night to cases where the red light of one vessel is opposed to the red light of the other, or where the green light of one vessel is opposed to the green light of the other, or where a red light without a green light or a green light without a red light is seen ahead, or where both green and red lights are seen anywhere but ahead. (b) If, when steam vessels are approaching each other, either vessel fails to understand the course or intention of the other, from any cause, the vessel so in doubt shall immediately signify the same by giving several short and rapid blasts, not less than four, of the steam whistle. This is com- monly known as the danger signal. (c) Whenever a steam vessel is nearing a short bend or curve in the channel, where, from the height of the bank or other cause, a steam vessel approaching from the opposite direction can not be seen for a distance of half a mile, such steam vessel, when she shall have arrived within half a mile of such curve or bend, shall give a signal by RULES OF THE ROAD 143 one long blast of the steam whistle, which signal shall be answered bj a similar blast given bj any approaching steam vessel that may be within hear- ing. Should such signal be so answered by a steam vessel upon the farther side of such bend, then the usual signals for meeting and passing shall immediately be given and answered; but if the first alarm signal of such vessel be not an- swered, she is to consider the channel clear, and govern herself accordingly. When steam vessels are moved from their docks or berths, and other boats are liable to pass from any direction toward them, they shall give the same signal as in the case of vessels meeting at a bend, but immediately after clearing the berths so as to be fully in sight, they shall be governed by the steering and sailing rules. (d) When steam vessels are running in the same direction, and the vessel which is astern shall desire to pass on the right or starboard hand of the vessel ahead, she shall give one short blast on the steam whistle as a signal of such desire; and if the vessel ahead answers with one blast, she shall put her helm to port ; or if she shall desire to pass on the left or port side of the vessel ahead, she shall give two short blasts of the steam whistle as a signal of such desire; and if the vessel ahead answers with two blasts, shall put her helm to star- 144 SMALL BOAT NAVIGATION board; or if the vessel ahead does not think it safe for the vessel astern to attempt to pass at that point, she shall immediately signify the same by giving several short and rapid blasts of the steam whistle, not less than four, and under no circumstances shall the vessel astern attempt to pass the vessel ahead until such time as they have reached a point where it can be safely done, when said vessel ahead shall signify her willingness by blowing the proper signals. The vessel ahead shall in no case attempt to cross the bow or crowd upon the course of the passing vessel. (e) The whistle signals provided in the rules under this article for steam vessels meeting, pass- ing, or overtaking are never to be used except when steamers are in sight of each other and the course and position of each can be determined in the daytime by a sight of the vessel itself or by night by seeing its signal lights. In fog, mist, falling snow, or heavy rain storms, when vessels cannot see each other, fog signals only must be given. (f) When two steam vessels are crossing, so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way of the other. (g) When a steam vessel and a sailing vessel are proceeding in such directions as to involve risk RULES OF THE ROAD 145 of collision, the steam vessel shall keep out of the way of the sailing vessel. (h) Where by any of these rules, one of the two vessels is to keep out of the way, the other shall keep her course and speed. (i) Every vessel which is directed to keep out of the way of another vessel shall, if the circum- stances of the case permit, avoid crossing ahead of the other. (j) Every steam vessel which is directed by these rules to keep out of the way of another ves- sel shall, on approaching her, if necessary, slacken her speed or stop or reverse. Emphasis should be laid upon paragraphs (h) and (i). The law prescribes that when one of two vessels must keep out of the way the other must keep her course and speed. The vessel that must keep out of the way shall, if the circum- stances permit, avoid crossing ahead of the other. The following rules are quoted from the Inter- national Rules. They apply in Inland Waters : 1. Notwithstanding anything in the rules every vessel, overtaking any other, shall keep out of the way of the overtaken vessel. Every vessel com- ing up with another vessel from any direction more than two points abaft her beam shall be deemed an overtaking vessel. In case of doubt, the vessel is to assume herself an overtaking vesseL 146 SMALL BOAT NAVIGATION 2. In narrow channels every steamer shall, when it is safe and practicable, keep to the side of the fairway or mid-channel which lies on the starboard side of such vessel. Sailing vessels underway shall keep out of the way of sailing vessels or boats fishing with lines, nets, or trawls. DISTRESS SIGNALS When a vessel is in distress and requires assist- ance from other vessels or from shore the following shall be the signals to be used or displayed by her, either together or separately: 1. In the Daytime a continuous sounding with any fog signal apparatus, or firing a gun. ^. At Night (a) Flames on the vessel as from a burning tar barrel, oil barrel, and so forth. (b) A continuous sounding with any fog sig- nal apparatus, or firing a gun. PRUDENCE AND PRECAUTION 1. In obeying and construing these rules due re- gard shall be had to all dangers of navigation and collision, and to any special circumstances which may render a departure from these rules necessary to avoid immediate danger. 2. Nothing in the rules shall exonerate any ves- RULES OF THE ROAD 147 sel, or the owner or master or crew thereof, from the consequences of any neglect to carry lights or signals, or of any neglect to keep a proper look- out, or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case. PENALTIES "Penalties are prescribed for the infringement of these rules by all nations that have adopted them as laws, and these penalties do not depend upon the question whether damage has or has not resulted from the infringement. " Where damage is done, and can be shown to be the result of neglect or violation of the rules, it is held, in the absence of proof to the contrary, to be the fault of the person having charge of the deck of the vessel offending, who will be considered guilty of a misdemeanor and punishable therefor. If death ensues, he will be subject to a charge of manslaughter. ** In every case of collision, it is the duty of the person in charge of each vessel to stay by the other and render such assistance as may be prac- ticable, provided he can do so without damage to his own ship, passengers, or crew. ** He is also required to give to the master of the 148 SMALL BOAT NAVIGATION other ship the name of his own ship and of the port to which she belongs, and the ports to and from which she is bound. " As soon as possible after the collision, he must cause an entry to be made in the log book, of the collision and of all facts connected with it." THI END 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. 12>teC)3fg ^CT 121966 3a RE' WED r-rO i-D NOVr-66-^Af; o A -5 P^ LOAN DEPT. 2W > ?er,55 W RECD LD MAR 1 9 ^65 -5 Plfl # MOV 4 19tib8 7 ^ REC'U DEC U '65 -3 PM LOAN DEPT. m- -frt^ tM-P- LD 21A-40m-4,'63 (D6471sl0)476B General Library University of California Berkeley i \ M168705 THE UNIVERSITY OF CALIFORNIA LIBRARY