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Problem 32. There are many ſecret ways by which Aſtronomers may date their letters to each other, ſome of them as follow. ☉ ♍ 5° 51'—if you receive a letter from your friend in the country thus dated, you look in the Nautical Almanac, and correct the Sun's motion the day in which it is in that ſign and degree, and find it was on the 29th of August, at midnight, in which he wrote it.—Again, ♄ 13° 10' ♍—This answers to September 22, at ſix in the afternoon——Again, the Dragon's Head in ♓︎ 8° 8', this will direct you to the 7th November, at noon—or, ☽︎ ♋︎ 2° 17'—☿ 8s 2° 12' this can be no other time than Decem. 10th, at noon; and many other ways you may invent from theſe examples, according to your fancy.
Problem 33. To find the Jewiſh hours by the Planisphere, viz. they divide the day, and night, be it long or ſhort, into twelve equal parts, from Sun-riſing to Sun setting, for the day, and from Sun-ſetting to its riſing for the night; thus, in the Equinoctial, the Jewiſh hours, and the common hours are alike in length, viz. 60 minutes; but, it is evident, when the Sun is in Cancer, the twelfth part of the day will be more than 60 minutes, and the night hours leſs, and they continually vary between the Tropics: thus, ſuppose at London the longeſt day is 16 hours, 26 minutes—multiply this by 60, and divide the product 986m by 12, and the quotient is 82m2⁄12 for the length of a Jewiſh hour by day under Cancer, and this is the length of the night hours under Capricorn; by this rule, we find a night hour under Cancer is 37 minutes,
