274 6EOORAPHY AND ASTRONOMY. zenith. Then bring down the 'edge of the quadrant of altitude to the other place, and the endof the quadrant shall out the ho- rizon in the true point of thecompass, and shew how the one bears to the other. So if you rectify the globe for the latitude and zenith of Barbadoes, you will find that Cape Finisterre in Spain, and Azoff in Muscovy, both lie in a direct line north-east from Barbadoes, according to this practice. But here let it.be noted, that though according to this sort of measuring, they both lie north -east from Barbadoes, yet they do net lie north-east of one another ; forif you rectify the globe for the latitude and zenith of Cape Finisterre, you will find Azoff lies near east- north-east fromCape Finisterre, or more than two points of the compass, (i. e. more than 221 degrees dif- ferent from the north-east.) And if a sailor or traveller who is at Barbadoes, should every league or mile of his way, by observing the compass, still make toward the north-east, he would come sooner to the He- brides or Western Scots Islands than to Azoff, or even to Cape Finisterre. But the course that he must really steer to come to Cape Finisterre is near north -east and by east : And if he could sail all the way clear to Azoff from Barbadoes, he must steer still much more to the eastward : All which things shew the mistake of solving this problem in this manner. Perhaps this may be made yet plainer to a learner, if we name two places which lie under the same parallel of latitude, viz. Madrid in Spain, and Pekin in China, latitude 40. Now these must always bear directly east and west from each other. But if you bring Madrid to the zenith, and having fixed there your quadrant of altitude, you bend it down to the horizon, it will not follow the course of the 40th parallel of latitude, and lead your eye to Pekin, but to much more southern places very far distant from Pekin, and which have a very different bearing, viz. to the Isle of Ceylon, &c. Upon this account, the best writers call that the angle of position between two places, which is found by the quadrant of altitude thus fixed at the zenith of any place; and drawn down to the horizon : But they describe the rhumb or course of bearing from one place to the other in a dif èrent manner, viz. It is that point of the compass, toward which any person must constantly bail or travel, in order to arrive at the distant place given. And without all doubt, this is the most just and exact account ofthings. Now in order to find this, it is sufficient for a learner to know, that if any one of the lines drawn from the points of the mariner's compass marked on the globe, (which are called rhumb lines) passes through both places, that line shews the course or bearing from one to the other, as the course from Cape St. Vint-
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