Essay on the Architecture of the Hindus c4.55

c4.55

Various rules have been laid down for the purpose of rectifying the variation of the shadow owing to the irregularity of the sun's motion in the ecliptic, the simplest of which seems to be as follows: The place where the shadow of the gnomon projects, on two successive days at the same hour, being marked, the difference between those two days, is taken as the variation of the shadow for sixty *ghaticas* or twenty-four hours. The interval between the times at which the western and eastern points were marked on the preceding day is multiplied by the difference of the shadow measured for one day, and the product being divided by sixty *ghaticas*, the result will give the difference of the shadow for the given time; it will then be only necessary to remove the eastern or western point so far towards the south or north, according as the difference of the shadow on the second day may be in either of those directions, or as the sun is in the southern or northern solstice.