. Mathematics, compiled from the best authors and intended to be the text-book of the course of private lectures on these sciences in the University at Cambridge [microform]. From half the sum of these six logarithms subtract thesine of half the difference of the true zenith distances, andthe remainder is the tangent of an arc. 6. Subtract the sine of this arc from the said half sum^and the remainder is half the true distance. 2. To find the time at a known meridian corresponding to thesame distance, and the difference oj longitude. In the Nautical Almanac the true distance of the moonfrom the
. Mathematics, compiled from the best authors and intended to be the text-book of the course of private lectures on these sciences in the University at Cambridge [microform]. From half the sum of these six logarithms subtract thesine of half the difference of the true zenith distances, andthe remainder is the tangent of an arc. 6. Subtract the sine of this arc from the said half sum^and the remainder is half the true distance. 2. To find the time at a known meridian corresponding to thesame distance, and the difference oj longitude. In the Nautical Almanac the true distance of the moonfrom the sun and certain fixed stars is calculated for evejsy SPHERIC ASTRONOMY. SOS three hours at ihe meridian of Greenwich ; and for anydistance intermediate to two of those, the correspondingtime is foun i by taking the proportional part of three hours,and adding it to the time oi the next preceding distance. Example. On the Tth of June, 1 795, at 18h. 20 10,the apparent altitude ol the moon was 22° 15, that of thesun 21° 35, their apparent distance 1 i9° 20 34, and themoons horizontal parallax 58; rehired the true uistance,and the longitude of the place. Describe the primitiveHZON, and draw thevertical ZN, and thehorizon HO. Set theDs altitude from O toM, and M is the ap-parent place of themoon. Draw the di-ameter M \, and BCperpendicular to it. De-scribe above HO theparallel circle ho, at theheight Hh — the sun- apparent altitude. Describe aUo theparallel circle be, at a distance from A equal to the supple-ment of the apparent distance of the moon from the , the intersection of be and ho, is the apparent place of thesun. Through the three points N, S, Z, draw the circleNSZ ; and through M, S, A, draw the circle MSA. ThenZSA1 is the first triangle. Set the correction of the moons altitude from M to m,and m is the 3 \s true place. Set tie correction of the sunsaltitude from S to s, and s is the suns true place. Throughthe points m and s draw the arc of a grea
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