Page:Description and Use of a New Celestial Planisphere.pdf/37

32 which is the length of a day hour under Capricorn; but, to find the length of thee hours at all times of the year by night and day, by the Planisphere, do thus: uppoe, for Example, on the first of August, at 10 hours, 12 minutes in the forenoon; I wish to know the exact time of day, according to the Jews?—Take the Semi-diurnal Arc, by Problem 8, which is 7 hours, 37 minutes, multiply this by 60, and divide the product, 457 minutes by 6, and the quotient is 76m$1/6$, for the length of a Jewih hour that day; then rectify the Planisphere to the hour and minute given, 10 hours, 12 minutes, A. M. and teady it there; then bring the director to the time of Sun-riing before found, 23 minutes pat 4, and carry it warily over 76 minutes, or 1 hour, 16 minutes, and it will then lay over 21 minutes before 6, and call this the first Jewih hour; then move it on 1 hour, 16 minutes more, to 5 minutes before 7, and call it the econd hour; then to 11 minutes after 8, and it ends the 3d hour; then proceed to 27 minutes pat 9, for the 4th hour; o now, as the director lays, you will plainly ee there is not another whole hour, before you come to our 12 minutes past 10; o count the odd minutes, till the director comes in a traight line with the 1t of Augut, the hour and minute given, and the Sun's place, and you find 45 minutes towards the 5th Jewih hour, with 31 minutes to come to finih that hour: by this rule, you will come at the true Chronological time motly made ue of in the Scriptures, and may reduce it, by this lat Problem, to our time of the day; o we find, at the Crucifixion of our Saviour, there was darknes