158 Journal of the Asiatic Society of Bengal. [N.S., XV, 
(d) In figure 4, OA =g represents a vertical gnomon 
(ganku), NOS and BOW are the north and south and east and 
west lines through the base of the gnomon. If OF =e is the 
equinoctial noon-day shadow (vishuvadbha) for northern lati- 
tude ¢, then FG, parallel to OW, is the locus of the equinoctial 
shadow, and the line BO =s8 represents = shadow at a time 
when the sun’s declination is south. Draw BH parallel to 
NS and denote BG by A; then BH = yf +e. The line 
BH = s. sin 6 is termed: the bhuja, BC = s. cos 6 the koti, 
and BG or A =s. sin 6 —e is termed the agra.* The angle 
FAO = 9, and BAO =z. 
Rules and problems. 
6. In this section we summarise the principal rules given 
in the siddhantas. 
A 
Fig. 4. 
&) The gnomon.—From figure 4 the following are ob- 
ined :-— 
= +(ssiné when B i th of H 
ee Soe 24%. WO). is north of ZW (the positive sign to be ~ 
