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THE MARINE RECORD. ee L METHOD FOR INDING, COMPASS ERRORS. §. // } ARRANGED FOR MASTERS AND PILOTS ON THE GREAT LAKES BY JOHN ROSS LATE MASTER LIGHT-HOUSE TENDER 9TH. DISTRICT. (Copyrighted 1897, all rights reserved.) CHAPTER I. PREFACE. The vagaries of the compass needle, especially on iron and steel ships, are a source of anxiety to all mariners; the loss of many lives and much valuable property 1s di- rectly traceable to ignorance of the derangement of the compass. Progressive masters and pilots on the Great Lakes have long felt the necessity of a practical knowl- edge of the compass and a method to find its error under the conditions which obtain on the Lakes. : The object of these notes is to make known a plain and simple method for finding the compass error, and, what is of more importance, one that is especially adapted for use on the Great Lakes. It is also intended to show that a practical knowledge of the compass can be easily ac- quired by any master or pilot, and that the finding of the compass error, and applying the error when found, is much more simple than many have been led to believe. In the writing and arrangement every consideration has been given to the peculiar conditions under which the Lake navigator labors; and for this reason nothing has been stated that is not applicable to Lake navigation. Technical terms have been used only where absolutely nec- essary to prevent confusion or misunderstanding. No attempt is made to explain the theory of the com- pass error. The practical hints on compasses and notes on magnetism, variation, and deviation, contain informa- tion with which every master and pilot should be familiar; they will assist a learner to find the compass error and may stimulate him to further enquiry. Those desiring to make a closer study of these subjects should consult the Reports of the Liverpool Compass Committee. Evan's Elementary Manual for the Deviations of the Compass in Iron Ships, Naval Professional Papers No. 13, and Lecky’s Wrinkles in Practical. Navigation, all of which have, in some way, contributed to these notes. Repetitions occur wherever it was thought they would serve to make the subject more easily understood. Lieutenant Glennie Tarbox, U. S. Navy, to whom the MS. was referred for criticism, has materially assisted in _ its preparation. JOHN ROSS. Washington, D. C., March 15, 1897. DEFINITIONS. The following terms are defined to prevent confusion: A “true bearing,’ or “true course,” is a bearing or course laid down on a chart without regard to’ variation or deviation. The compass roses on the charts of the _ Lake Survey.are for true bearings and: courses. -If a true bearing or course be taken from the chart, and the variation at the place where the bearing or course is laid down be applied, the resulting bearing or course will be-a magnetic bearing or magnetic course. Or, a magnetic bearing or magnetic course is a true bearing or course to which has been applied the variation. _A “compass bearing” or “compass course” is a bearing or course.shown by the compass whether the compass is, or is not, compensated. The-difference between a magnejic bearing and a com- pass bearing, or between a magnetic course and a compass course, is the deviation or compass error. Whenever the words compass error are tised ther apply to the deviation alone and not to the combined ‘ariation and deviation. - The words compass error and deviation are used indiffer- ently to express the same thing. The words vessel and ship are used indifferently to express the same thing. COMPASSES, THE STANDARD COMPASS. Every iron or steel vessel should have at least two compasses, the standard and the steering. The standard compass should in every case be the navigating compass. It should be a liquid compass with card 7% inches* in diameter, well balanced, sensitive in smooth and steady in heavy weather; or a dry compass with card 10 inches in di- ameter and possessing the same qualities. Either liquid or dry compass should be from some reliable maker; it pays to get the best. The compass card should read to degrees in addition to the points, and the degree marks should be clearly defined, not blurred. A simple test for a com- pass is to place it in position, and with a jackknife or piece of iron deflect the needle; remove the knife or iron quick- ly and note the time it takes the card to come to rest at the exact degree it started from. If the card is very slow in coming to rest or does not return to the exact. degree it started from, something is wrong with. the compass. The standard compass should be fitted with an azimuth circle, i. e., a circle for taking direct bearings of any object. : HE STANDARD COMPASS BINNACLE. The best binnacle is one that will admit of compensating for the deviations by placing the magnets inside the bin- nacle instead of placing them about the deck. In these binnacles the deviations can be compensated by practical methods which are explained by the instructions furnished with the binnacle by the manufacturer or his agent. The ordinary standard binnacle should be of bronze or brass, high enough for the compass to be higher than the rail, and with a stand heavy enough to prevent vibration. The hood (top) of the binnacle should fit so as to be easily removed, and so as to leave the top of the compass, when level, well above the binnacle. The hood should also be fitted so that.an alidade can be shipped on its top, care be- ing taken to have the lubber’s mark on the hood to co- incide with the lubber’s mark on the standard compass. MOUNTING THE STANDARD COMPASS. In lake navigation, where courses are changed much more frequently than on ocean routes, it is advisable to mount the standard compass on the top of the pilot house. where it is accessible at all.times to the officer on watch, and is least obstructed for an all-around view. It is very desirable (as will be seen farther on) that a’ directly ahead bearing be obtained; but the compass should in all cases be placed on the midship line. [he binnacle should be placed far enough from the edge of the pilot house to permit taking bearings in every direction; it should also be so far from the steering com- pass that the magnets used for compensating the standard compass will not influence the steering compass. It may here be remarked that the. position of deck beams should not .enter into consideration when a posi- tion for the binnacle is selected; the deck under the bin- nacle can be easily strengthened to give a firm hold to the bolts securing it. Every sailor knows that as little iron as possible should be used in the construction and fittings of a pilot house, and that the hand rail around it should be either of brass or wood; but a hint to designers and superintendents of construction may not be out of place. Iron that is subject to temporary removal or change of old position should be at least 15 feet from the compass. No iron smoke pipes, ventilators, stands for engine-room indicators, bells, or whistles should be near the position selected for the standard compass. If necessary to have them they should be of bronze or brass. Inside the pilot house no lockers should be built near the place selected for the steering compass or any stow holes left to drop things into. The stand, wheel, spindle, and shafting of the steam steering gear should be of brass for a distance of 8 feet from the compass. The system ef double wires should be employed in all electric installations on board ship and no single electric wires should lead anywhere near the standard or other compass. Even in well placed standard compasses on iron and steel ships the deviation is often from 3 to 4 points before compensa- tion. Before securing the binnacle to the deck for a full due, it might be well to get the opinion of an expert as to the best position for it, without losing sight of its con- venience for use by the officer on duty. — - THE STEERING COMPASS. The steering compass should be a liquid compass of reliable make, with a card 7% inches in diameter marked for degrees, and possessing the same qualities in smooth and rough weather as the standard compass. In long steamers (which do not yaw badly in a heavy sea) courses should be steered to degrees; practically, greater. accu- racy is obtained by steering to degrees and, where pos- sible, courses to degrees should be taken from the charts. Where the compass rose on the chart is not marked to degrees the navigator can use the isinglass compass (in common use under several names) to take off the course. MOUNTING THE STEERING COMPASS. As much consideration as possible should be’ given to lessen the iron near the compass. If there is a steam coil in the pilot house the tubing should be of brass or copper; stands for engine-room indicators and bell or. whistle pulls should not be of iron; it is important that sash weights for windows should not be of iron. The steering compass in iron or steel vessels should if possible be amidships and its lubber’s mark in the fore and aft line. The compass needle should be at least 3% feet from iron deck beams and as far as possible from vertical iron. Whether there is only one steering compass, or two, it is of the besos» importance that it be placed so that the lubber’s mark and the point directly opposite are in a fore and aft dine. The binnacles for sfeering compasses should be provided with good lights. (To be Continued.) a NOTES. Efforts are being made to have the authorities at Wash- ington take possession of old Fort Mackinac, and make it a regularly garrisoned army post. Many people thought that it already was one, but it was abandoned two years ago. The overflowed regions of the Mississippi are again as- suming their wonted activity. The levees are being re- paired as the water recedes, and the people who have been camping on the higher ground will return to their homes in what may be considered the lowlands, or lard lower than the bed of the river. The Hydrographic Office, Navy Department, has just issued the N. Pacific pilot chart for June, and if such a thing is possible, it seems to contain more special informa- tion than some previous issues. The location of the dere- lict schooner General Siglin, is given on May 5, off Queen Charlotte Islands, in latitude 53 degrees north, longitude 153 degrees 30 minutes west-. Commander Craig, U. S. N., Hydrographer, is to be complimented on the com- pilation of the valuable data contained in the June chart. The word “ton,” as applied to the measurement of vessels, has a certain definite meaning, well settled by cus- tom, as also, the United States Circuit Court of Appeals holds (the Thomas Melville), by the navigation laws of the United States, and it means 100 cubic feet of interior space. The entire cubic contents of the interior space, numbered in tons, is called the “gross tonnage.” When from the entire cubic contents of the interior of a vessel, there are deducted the spaces occupied by the crew and propelling machinery, the remainder, numbered in tons, is called the “net tonnage.”—Business Law Weekly. The American Protective Tariff League has just issued, in document form, the speech of Senator Elkins, of West. Virginia, on the subject of the American Merchant Marine and Discriminating Duties. This is a complete presenta- tion of the benefits of discriminating duties as pledged by the Republican platform. Any of our readers can ob- tain a. copy for 2 cents. Ask for Document No. 44 and address W. F. Wakeman, General Secretary, 135 West 23d street, New York. ; _ According to some authorities Stephen Crane depicted the feeling of a soldier in battle better from his imagina- tion alone, than others had done it from actual experience. Those who read “The Open Boat,” in the June number of Scribner’s Magazine, will agree that he has pictured the sensations of the shipwrecked better from his own experi- ence of it, than others have achieved it by force of imagi- nation. It is a remarkable tribute to his cleverness that he should have succeeded equally in pure imagination and in a transcript of reality. This is the first elaborate ac- count of his terrible experience, after the wreck of the steamer “Commodore” when on its way to Cuba, It has taken a clever Frenchman to discover a kind of barometer which may be safely called unique, Harper’s Round Table says. An English journal says that it is noth- ing more nor less than the figure of a general made of gingerbread. He buys one every year, and takes it home and hangs it by a string on a nail. Gingerbread, as every one knows, is easily affected By changes in the atmos- phere. The slightest moisture renders it soft, while in dry weather it grows hard and tough. Every morning, on going out, the Frenchman asks his servant, “What does the general’say?” and the man applies his thumb to the gingerbread figure. Perhaps he may reply, “The general feels soft. He would advise you taking an umbrella.” On the other hand, if the gingerbread is hard and unyielding to the touch, it is safe to go forth in one’s best attire, um- brellaless and confident. The Frenchman declares that the general has never yet proved unworthy of the confidence placed in him, and would advise all whose purse will not allow them to purchase a barometer or aneroid, to see what -the local baker can do for them in the gingerbread line.