778 
Ancient Observatory at Delhi. 
[December, 
their inner surface, so that, while the exterior plan of each 
tower would be represented by a circle, a cogged wheel 
would show the shape of the floor inside. 
From a certain spot on the flight of steps running up the 
gnomon, the central pillar of each tower can be observed as 
being truly level with its surrounding wall. From this spot 
another peculiarity can be seen : — The projecting teeth of 
Fig. i. — Ground Plan of Towers. Scale (Natural). 
Shaded portions brickwork ; dotted parts rank grass and filth. 
A. Centre of pillar. a b. Radius of pillar, 32^5 inches. A c. Radius of 
interior of tower, 325 inches. a d. Radius of cogs, 350 inches. 
A e. Radius of exterior of tower, about 360 inches. af. Unoccu- 
pied interval, about 130 inches, x x , &c. Raised sectors with “ ivory ” 
cement covering. 
the imagined cog-wheel are apparently the same as the 
intervals between them. Both the towers seem in every 
respeCt alike, except that the nearest of the two towers has 
its northern cog in a line with us and its central pillar, 
while the furthest tower has one of the intervals between 
