. A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects. t; the log wasthrown only to help make up that judgment, for the rate at the timethe log was thrown may have been considerably more or less thanthe average motion during the hour. The course of a ship is marked by the mariners compass. The mariners compass differs from the surveyors compass onlyby its construction, that is, the magnetic needle is the motive powerin both. In consequence of the motion of a ship at sea, the mari-ners compass is suspended in a double bo
. A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects. t; the log wasthrown only to help make up that judgment, for the rate at the timethe log was thrown may have been considerably more or less thanthe average motion during the hour. The course of a ship is marked by the mariners compass. The mariners compass differs from the surveyors compass onlyby its construction, that is, the magnetic needle is the motive powerin both. In consequence of the motion of a ship at sea, the mari-ners compass is suspended in a double box, moving on a doubleaxis, one at right angles with the other, the whole balanced by acentral weight which keeps the compass card nearly steady and hori-zontal, whatever be the motion of the vessel. The card is attached to the needle, and is moved by the card is divided into 32 equal parts, called points, and to readover these points in order, is called by seamen, boxing the compass,and to know the north star and box the compass is too often theamount of the common sailors knowledge of navigation. 178 The figurebefore us re-presents thecard of them a riner*scompass. Thefour quadrantpoints aremarked by asingle letter asJV. for north,E. for midwaypoints betweenthese by twoletters, as for north-east, JV. W. for north-west, &c. One point either way from any oneof these eight points is marked by the word by. Thus, JV. by E. isone point from the north toward the east, and it is read north byeast; S. E. by S. indicates one point from the south-east more tothe south, and it is read south-east by south ; W. by JV. means westone point toward the north. To box the compass we begin at any point, as north, and mentionevery point in order all the way round, thus : North; north by east; north north-east; north-east by north; north-east ; north-east by east; east north-east; east by north ; east, &c. A point of the compass is 11° 15, which is subdivided
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Keywords: ., boo, bookcentury1800, booksubjectnavigation, booksubjectsurveying
