CHAPTER IX-CALCULATIONS RELATING TO SHADOW8 . 279 The rule for arriving at the measure of the shadow correspond. ing to a time (of day) given in ghattis. 18. The measure of the style is divided by twice the measure of the given) portion of the day ; (from the resulting quotient) he measure of the style is subtracted, and (to itb) the (equinoctial noon-shadow is added. This gives rise to the measure of the shadow at the required time of day. An example in it.stration thereof. 19. If, in the case of a style of 12 digulas, the (equinoctial) shudow is 2 digul8what is the measure of the shodow (of the style) at a time when i0 ghati8 bave elapsed or have to elapse, the duration of the day-time being 80 gifi8? IThe definition of the measure of a man's foot in relation to measurements carried out by means of the foot-measure a8 involved in the shadow. 20. One seventh of the height of a person happens to be the length of that person's foot. If this be Bo, that person shall be fortunate. (Thus) the measure of the shadow in terms of the foot measure is obvious. 'The rule for arriving at the numerical measure of the shadow which ha8 ascended up (a perpendicular wall) . 21. (The height of) the style is multiplied by the measure of the human shadow (in terms of the man's height). The resulting) 18. Algebraically a + e , where g in the measure of the time of 2 ५ the day in ghadia. This formula may be seen to follow from that given in the note to stanza 15 above. ¢ < b 2. Algebraically, h= where a in the altitudo of the shadow casting style, a the height of the shadow on the wall, b the measure of the human shadow in terms of the man's height, and ० the distanee be tween the pillar and the wall. The diagram here given eluci dates the rule. It has to be noted here that the distance
- between the pillar and the all
has to be measured along the ine of the shadow which is cant im unlight
