[Editor's note: The following information was extracted from the named books found on Google Books by using their 'clip'feature. It extracts the text using a pretty good OCR, but it doesn't get punctuation marks, new paragraphs, or special characters such as the degree symbol or small-type fractional numbers. I have tried to add the missing info to this text, but I may have missed some areas. You can find the books on Google Books and see the original if my transcriptions aren't clear enough.] ================================================================================================= The American practical navigator By Nathaniel Bowditch, George Wood Logan, United States. Navy Dept. Bureau of Equipment; 1906 THE NAVY SERVICE 7-1/2 INCH LIQUID COMPASS This consists of a skeleton card 7-1/2 inches in diameter made of tinned brass resting on a pivot in liquid with provisions for two pairs of magnets symmetrically placed. The magnet system of the card consists of four cylindrical bundles of steel wires these wires are laid side by side and magnetized as a bundle between the poles of a powerful electromagnet They are afterwards placed in a cylindrical case sealed and secured to the card Steel wires made up into a bundle were adopted because they are more homogeneous can be more perfectly tempered and for the ame weight give greater magnetic power than a solid steel bar Two of the magnets are placed parallel to the north and south diameter of the card and on the chords of 15 nearly of a circle passing through their extremities These magnets penetrate the air vessel to which they are soldered and are further secured to the bottom of the ring of the card The other two magnets of the system are placed parallel to the longer magnets on the chords of 45 nearly of a circle passing through their extremities and are secured to the bottom of the ring of the card. The card is of a curved annular type the outer ring being convex on the upper and inner side and is graduated to read to one fourth point, a card circle being adjusted to its outer edge and divided to half degrees with legible figures at each 3 for use in reading bearings by an azimuth circle or in laying the course to degrees. The card is provided with a concentric spheroidal air vessel to buoy its own weight and that of the magnets allowing a pressure of between 60 and 90 grains on the pivot at 60 F the weight of the card in air is 3,060 grains The air vessel has within it a hollow cone open at ite lower end and provided with the pivot l earing or cap containing a sapphire which rests upon the pivot and thus supports the card the cap is provided with adjusting screws for accurately centering the card The pivot is fastened to the center of the bottom of the bowl by a flanged plate and screws Through this plate and the bottom of the bowl are two small holes which communicate with the expansion chamber and admit of a circulation of the liquid between it and the bowl The pivot is of gun metal with an iridium cap. The card is mounted in a bowl of cast bronze the glass cover of which is closely packed with rubber preventing the evaporation or leakage of the liquid which entirely fills the bowl This liquid is composed of 45 per cent pure alcohol and 55 per cent distilled water and remains liquid below 10 F The lubber's line is a fine line drawn on an enameled plate on the inside of the bowl the inner surface of the latter being covered with an insoluble white paint. Beneath the bowl is a metallic self adjusting expansion chamber of elastic metal by means of which the bowl is kept constantly full without the snow of bubbles or the development of undue pressure caused by the change in volume of the liquid due to changes of temperature The rim of the compass bowl is made rigid and its outer edge turned strictly to gauge to receive the azimuth circle. THE DRY COMPASS The Lord Kelvin Compass which may be regarded as the standard for the nonliquid type consists of a strong paper card with the central parts cut away and its outer edge stiffened by a thin aluminum ring The pivot is fitted with an iridium point upon which rests a small light aluminum boss fitted with a sapphire bearing. Radiating from this boss are 32 silk threads whose outer ends are made fast to the inner edge of the compass card; these threads sustain the weight of the suspended card and as they possess some elasticity tend to decrease the shocks due to motion. Eight small steel w ire needles 3-1/4 to 2 inches long, are secured normally to two parallel silk threads, and are slung from the aluminum rim of the card bv other silk threads which pass through eyes in the ends of the outer pair of needles. The needles are below the radial threads, thus keeping the center of gravity low. ================================================================================================= Remarks on Engineers' Surveying Instruments By Heller & Brightly, Heller & Brightly SURVEYOR'S COMPASS In a good surveyor's compass the slits of the sights should be precisely in a line with the two zero lines of the ring, and these sights at right angles to the main plate. It should be as light as is consistent with strength and steadiness. The magnetic needle is, however, the main point and any one of the following defects will prevent its free working - bad steel, too great heat in forging, improper tempering or defective magnetism. We sometimes receive communications from parties wishing to make magnetic needles the following will give them the information sought for. The steel should be either of shear or the best cast steel converted from Swedish Danemora iron (shear steel being the best however). If the needle is forged into shape care should be taken not to overheat it during that process After filing and finishing into shape and length it is to be hardened and tempered and it is this operation that is most liable to be improperly performed the needle being so thin that it is apt to get too hot in places and burnt steel never magnetizes properly. Our own method is to heat a crucible of lead to a cherry red color and to heAt the needle therein and when it is to the proper heat plunge it into water, -- the beauty of this method being that even though the needle be allowed to remain a considerable time therein it can never attain a greater heat than the lead itself has. After hardening the needle should be tempered. A good iule for the degree of hardness to which the steel is to be reduced is this: when the length exceeds thirty times the thickness to temper to dark red, or red blue, when the length is under this to leave them untempered. In magnetizing two methods can be employed, first, by passing over each end the opposite pole of a fixed magnet; second, by a magnetic coil. If the first method be the one employed. a thin film of oil on the needle during magnetizing will greatly increase the power; but the method that is most certain of thoroughly magnetizing to "saturation" and with no possibility of "different polarities" being developed, is by passing the needle through a magnetic current. To any one who wishes to make a coil for this purpose the following hints may be useful. A cylindrical coil of copper wire as thick as it is long.-- this cylinder to have a bore equal to its thickness, (the copper wire to be rather thick. Our own coil is of 1/8 inch thick wire).-- The exciting power to he a voltaic apparatus on Groves principle (platina and zinc); and the needle to be magnetized passed up and down the interior of the copper cylinder. After being magnetized it is necessary to know if this has been done properly (i.e., if the latent magnetism of the needle has been fully developed and if this magnetism is permanent) to prove the first the needle should lift a certain amount of soft iron; (our own needles will lift ten times their weight). Second after noting the amount raised on first magnetizing it should be tried after say a week's time, and it should then have lost but little of its power. It must be recollected, that a soft untempered needle loses almost all its magnetism within a comparatively short time, though at first it will develop as much, if not more than a tempered one.* The pin and the cap on which the pin works require a peculiar shape; the centre of the cap to be at as obtuse an angle as possible, consistent with having a proper centre, and this centre perfectly smooth; the centre pin to have a hard round smooth point; and this point with not too obtuse an angle. Defects of these two last (cap and pin) are in eight cases out of ten the cause of the dull working of the needle. To preserve the fine point of the centre pin from unnecessary wear or from being accidentally broken off, never jolt nor carry the compass without being sure that the needle is screwed oft the pin. In using the needle, lower it carefully, so that it gently rests, and does not fall upon the centre pin. To prevent unnecessary wear of the centre pin, check the needle on fust letting it down at the mean of its swing (i.e., if the needle swings from say 0 to 30, check it by raising it off the pin by means of its screw at 15; gently let it down again and it will be within a few minutes of its proper settling place). Never allow the needle to be played with by a knife or a piece of iron 0r steel, for two reasons; first the instrument should never be made a plaything; second, every near passing of a piece of iron or steel removes a portion of the Magnetism of the needle almost the entire magnetism can be removed by a ne ries of such passings A needle should never excepting lor special purposes be more than six inches long it being very difficult to magnetize properly beyond this length without developing different polarities on the same side of the needle A live inch length is very good ?e sure that nothing to attract the needle is carried on the person in the hano of penknives watch chains buttons or iron rivets in the magnifier used to read the graduations Of late years new causes of error from this have arisen The new watches in which the movements are made of nickel are almost as powerful in attracting the needle as if these movements were made flí iron The felt hat makers modern fashion of stiffening the rims of their hats by inserting around the edge a small iron wire the extra broad brimmed tirmed the military or Burnside hat should especially be tabooed shouH make the Surveyor examine both his hat and watch There is one source of error which even the manufacturer must have a special apparatus to detect and this apparatus is as essential a part of his equipment a a lathe This is a sensitive mounted magnetic needle and every piece of brass even of the smallest size is tested by being brought near to this needle in ordei to see whether any magnetic attraction is concealed The brass founder is the one here in fault as impure copper or the smallest piece of iron such as ? tack core wire or stirring his melted crucible with an iron rod will engender tlm cause These impurities melting and diffusing throughout the brass although imperceptible to the eye nre brought to notice by the searching influence of the test needle All the surveyors Compasses made before the last 80 years are especially liable to error from this cause those made by Bittenhouse are however notably free from it and those who own any such should have them tried by some maker's test needle to prove their freedom from it It would be a matter of surprise to some to know how many needle instru meats are defective from this cause and we will give one instance thai occurred lately. An English Compass venerable with age and the associations connected with it had been constantly used by a Surveyor for over 50 years and by his father before him This Compass was held in such repute that all the farm lines in a radius of 100 miles had been established by it In fact the Surveyor and his Compass were held in such veneration as to be called in to settle every land dispute in the neighborhood and the judgment of the two was considered final At last the old Surveyor died and such was the desire of the surrounding land Surveyors to possess this Compass that at the auction sale of his effects it was sold for treble the price a new one could have been bought for. The fortunate possessor brought it to us for cleaning and adjusting and some vagaries that took place in the adjusting induced us to give the instrument a thorough examination and we found that this defect of impure metal was present in such a marked degree that in turning the instrument on its centre it was sufficient to draw the needle from its proper position from 10 minutes to 4 deg. (in some spots 5 deg.)**. We are not surprised to hear since the old Surveyor's death that several lawsuits are in progress in this locality from land disputes. One common error of Surveyors is to choose a heavy needle this is a mis take A heavy needle soon wears out the fine point of the centre pin The superficial surface and not the weight of the needle determines the amount of magnetism it is capable of receiving. One simple effect has sometimes bothered the young Surveyor His needle will sometimes not traverse but will persistently stick to the under side of the glass or one end at the lightest provocation would fly up to the glass and remain there This is caused by the glass becoming charged with electricity from rubbing against the clothing or being rubbed by a silk handkerchief Touching the upper part of the glass in several places with the moistened finger tip or breatb ing on the glass will remove the electricity. **This unequal attraction is one of the worst features in this imperfection if the iron were equally distributed throughout the metal the attraction bcing equal the needle would still point true. *If the reader wishes to investigate thoroughly the subject of magnetism and magnetic needles he will find ample material in the works of Seoresby Sabine Brewster or the Eaejo Writtanioa art Magnetism ================================================================================================== A manual for northern woodsmen By Austin Cary 2. ADJUSTMENTS OF THE COMPASS A compass in first class order will meet the following tests: a. The plate must be perpendicular to the axis of the socket. b. The plane of the level bubbles must be perpendicular to the same axis. c. The point of the pivot must be in the center of the graduated circle. d The needle must be straight. e The sights must be perpendicular to the plane of the bubbles. In these tests it is presupposed that the circle is accurately graduated and that the plane of the sights passes through the zero marks These are matters that belong to the maker of instruments and in all modern compasses accurate adjustment of them may be assumed. The general principle of almost all instrumental adjustments is the Principle of Reversion whereby the error is doubled and at the same time made more apparent Thorough mastery of this principle will generally enable one to think out the proper method of adjusting all parts of any surveying instrument In the case of the compass the above named tests may be applied and the instrument adjusted as follows The order of the adjustments is essential. THE SURVEYOR'S COMPASS a. The plate is exactly vertical to the spindle in a new compass but the soft metal of most instruments is liable in use to become bent. If that occurs to any considerable degree, it will be shown by the needle and the bubbles. The instrument should then be sent to the maker for repairs. b. To make the plane of the level bubbles perpendicular to the axis of the socket, level the instrument, turn it 180, and, if the bubbles are out, correct one half the movement of each by means of the adjusting screw at the end of the bubble case. Now level up again and revolve 180, when the bubbles should remain in the center. If they do not, adjust for half the movement again and so continue until the bubbles remain in the center of their tubes for all positions of the plate. c,d. When the pivot is in the center of the circle and the needle is straight, the two ends of the needle will cut the circle exactly 180 apart in whatever position the instrument may be set. If the needle does not so cut, one or both of these conditions is not fulfilled. If the difference between the two end readings is constant for all positions of the needle, then the pivot is in the center of the circle but the needle is bent. If the difference in readings is variable for different parts of the circle, then the pivot is off center and the needle may or may not be straight. To adjust the pivot, first find the position of the needle which gives the maximum difference of end readings; then using the small brass wrench commonly supplied with the compass, bend the pivot a little below the point at right angles to the direction of the needle until one half the difference in end readings is corrected. Repeat the test and adjust again if necessary. When the needle cuts opposite degrees, or when it fails to do that by a constant quantity in all parts of the circle, the pivot point is in the correct position. With the above adjustment attended to straighten the needle. To do this, set the north end of the needle on some graduation mark and bend the needle until the south end cuts the circle exactly 180 from it. e. To make the sights perpendicular to the plane of the bubbles level the instrument carefully, hang a plumb line some feet away, and then look through the sights upon it. If the plumb line appears to traverse the forward slit exactly. that sight is in adjustment. If not, file off the base of the sight until the adjustment does come. Then revolve the compass 180 and test the other sight in the same manner 3 KEEPING THE COMPASS IN ORDER Sharpening Pivot. The pivot or center pin of a compass much in use is liable to become dulled so that the needle does not swing freely. To obviate this the needle should always be raised off the pivot when the compass is being carried. A much blunted pivot should be handed over to a jeweller to be turned down in a lathe, but ordinary sharpening can readily be accomplished by the surveyor himself with the aid of a fine whetstone and the small wrench usually supplied with a compass, or a pair of pliers. The pivot should be removed from the compass box and fixed in the end of a small, split stick; the point may then be sharpened by twirling it gently on the stone at an angle of about 30 with its surface. When the point is made so fine and sharp as to be invisible to the eye, it should be smoothed by rubbing it on the surface of a soft clean piece of leather. Remagnetizing Needle. Dullness of the needle may be due to the fact that it has lost its magnetism and needs to be recharged. For this purpose a permanent magnet is required. The north end of the needle should be passed several times along that pole of the magnet which attracts, it and the south end passed similarly over the opposite pole. The passes should be made from center to end of the needle, and a circle described in bringing the two ends successively into contact. In order to prevent the loss of magnetism, the needle of a compass not in use for a considerable time should lie in the north and south direction. Balancing Needle. The needle is commonly balanced on the pivot by a fine brass wire wound around the south end. If change of latitude is made, the balance will be destroyed and the wire may be shifted to make adjustment. Replacing Glass. In case of emergency a piece of window dowglass may be cut down with a diamond and ground on a grindstone to fit its setting. It may then be set in place, with putty if possible, and the binding ring sprung into place over it. =================================================================================== Defects and disadvantages of the present form of tripods for field-instruments By Heller & Brightly, math. inst. makers, Philadelphia, Heller & Brightly A needle should never excepting for special purposes be more than six inches long, it being very difficult to magnetize properly beyond this length without developing different polarities on the same side of the needle. A five inch length is very good. One common error of Surveyors is to choose a heavy needle; this is a mistake. A heavy needle soon wears out the fine point of the centre pin. The superficial surface and not the weight of the needle determinee the amount of magnetism it is capable of receiving. ============================================================================== 14 December 1944 UNITED STATES COAST GUARD SPECIFICATION FOR COMPASSES: MAGNETIC, LIQUID FILLED, MARINERS, COMPENSATING, FOR LIFEBOATS (WITH MOUNTING) FOR MERCHANT VESSELS E-lc. Jewel and Pivot - The pivot and jewel chamber shall be fitted with a sapphire, synthetic sapphire, or hardened glass jewel. The hardness of the jewel shall be not less than 8 on the Moh's scale. The jewel shall have a high polish and shall contain a suitable central depression to receive the pivot point. A pivot of stellite, osmium, iridium, or platinum alloy shall be used. The chamber, pivot arrangement, and moving element shall be so designed as to maintain a static balance in a horizontal plane and to permit the card to incline not less than 10°. Pivoting shall center at the intersections of the coordinate diameters. E-ld. Magnets - All magnets shall be made of suitable magnet steel such as cobalt or alnico steel, and shall be suitably aged and suitably balanced to comply with paragraph E-21 and F-la(5). Magnets shall be magnetized to saturation and reduced 30 to 10% of the maximum theoretical magnetic moment, in such a manner as to insure permanence of magnetic properties. Magnets used on the same card shall be balanced within 2% of each other. E-if. Filling Liquid - The compass bowl shall be filled with either a compass fluid conforming to the requirements of paragraph F-10 of Federal Specification TT-R-58, or a Grain alcohol-distilled water combination which will meet satisfactorily the requirements of paragraph F-10 (with exception of paragraph F-10(2) of above specification). E-Ij. Instructions for Finding Compass Error - The following instructions shall be permanently engraved in plastic and mounted conspicuously on the binnacle: "To find compass error using the sun, moon, star or cloud while near the horizon. Suppose the sun is rising and the compass is mounted in place. Head boat west by compass and you decide the sun is bearing 70° by the compass. Head boat east by compass and suppose the sun bears 100°. These added together make 170° and when halved makes 85° which is the correct bearing of the sun at that moment. Now suppose you want to steer S.W. Head the boat 225° by compass and take another bearing of the sun. It now bears 65°; it should bear 85°. Therefore the compass card is turned 20° too far to the right giving a 20° error, thus you should steer 20° to the left to offset it or 205° by compass to make good 225°, the direction you want. If it is desired to remove this error, proceed as outlined in manufacturer's instructions." E-2. Performance Requirements E-2a. Pivot Friction - When the compass is deflected 5° in either direction at each cardinal point, the card shall in all cases return to its original position of rest within 1°, without tapping. E-2b. Accuracy - When tested in accordance with paragraph F-la(l), the combined calibration and centering error in any direction shall not exceed 2°. ============================================================================ The Plain Compass From A Manual of the Principal Instruments used in American Engineering and Surveying The 1878 catalogue of W. & L.E. Gurley, Troy, New York THE MAGNETIC NEEDLE.—The forms of the needle are almost infinitely varied, according to the taste or fancy of the maker or surveyor, but may be resolved into two general classes, one having the greatest breadth in a horizontal, the other in a vertical direction. We have usually made our needles about one-twentieth of an inch broad. and one-third as thick, parallel from end to end, the north and south poles being distinguished from each other, by a small scollop on the north end. Of course the form of the needle is always varied according to the choice of our customers, and without additional charge. The length of the needle varies in different instruments, from four to six or even seven inches, those of five and a half, or six inches long, being generally preferred by surveyors. The movement of the needle, with the least possible friction, is secured by suspending it, by a steel or jewel centre, upon a hardened steel pivot, the point of which is made perfectly sharp and smooth. The test of the delicacy of a magnetic needle is the number of horizontal vibrations, which it will make in a certain arc, before coming to rest —- besides this most surveyors prefer also to see a sort of quivering motion in a vertical direction. This quality, which is manifested more in a horizontal, than in a vertical needle, and depends upon the near coincidence of the point of suspension with the centre of gravity of the needle, serves to show merely that the cap below is unobstructed. ===========================================================================