Page:Description and Use of a New Celestial Planisphere.pdf/38

33 from the 6th hour until the 9th hour; now, by this Problem, we learn, that the 6th hour ended at the Semi-diurnal Arc, or when the Sun was on the Meridian at noon; and the 9th hour was a few minutes after 3, by an equal Hour Clock; inamuch as it was near the Vernal Equinox. But, the Arithmetical way to find the Jewih hour and minute, is thus—find how many of our hours and minutes the day conits of; then ay, as thee hours and minutes are to 12 hours, o is the hours and minutes ince Sun-riing, to a fourth proportional, the Judaical hour required; but oberve, the time gained as above, is only that hewed by a clock or watch that goes equal hours at the place where the occurrence happened; but to find the real time of day at another place, (uppose London), we must find the difference of Longitude of the two places, and turn it into time, at the rate of 15° per hour; o, Jerualem, being 35° 20' Eat of London, or 2h 21m 20s in time earlier, this mut be ubtracted from the time given by their equal hour clock, and the remainder will be the time at London, as though their ninth hour, at that time of the year, ended at 8m after 3 in the afternoon, subtract 2h 21m 20s from 3h 8m, and the remainder is 46m 40s after 12 at noon at London.

Problem 34. To find the Horary Angle, or the apparent time from noon by a ingle Altitude of the Sun; for which purpose, Mr. 's Patent Quadrant is the best intrument by land, as well as by ea, it having an artificial Horizon, which the common Hadley’s Quadrants have not; but if one should have a Collins's or