vs. 12-15 ] the Sun's altitude should be obtained contrarily (i.e., by revers ing the laws of addition and subtraction). The first part of the rule relates to the case when the Sun is in the nor thern hemisphere and lies between the local and equatorial horizons, i.e., shortly after sumrise or before sunset. 49 The second part of the rule indicates the method to be used for finding the Sun's altitude in the night. The details of the method are given by the
- (When the Sun is) in the northern hemisphere, having calculated the
Rsine of the given mocturnal aऽus (i.e., those clapsed since sunset in the first half of the might or those to clapse before sumrise in the second half of the might) as increased by the (Sun's) ascensional difference, (thern) multiplying (that) by the day-radius and dividing by the radius, then from the (resulting) guotient subtracting the earthsine, and (finally) multiplying the remainder by the Rsine of the colatitude and dividing by the radius is obtained the Rsine of the Sun's altitude. (When the Sun is) in the southern hemisphere, the (Sun's) ascensional difference and the earthsine are (respectively) subtractive
The Rsine of the Sun's altitude in the might is required (i) in the calcu lation of the elevation of the lunar horms, and (2) in the calculation of the solar eclipse. A rule for calculating the time elapsed since sumrise in the fore moon or to clapse before sunset in the aftermoon with the help of the shadow of the gnommon : 12-15. By the divisor, which is the suare root of the sum of the sपuares of the grnommon and its shadow, should be divided the radius multiplied by the gnormon: (the result is) the Rsine of the Sun's altitude. From that are obtained the ghas (of the time elapsed since sunrise in the foremoon or to clapse before sunset in the aftermoon) (by proceeding) conversely (to Rule 7-10) (in the following manner): C. MBh, i. 26. The Rsine of the Sun's altitude should be multiplied by the radius and divided by the Rsine of the colatitude. In the
