994 Journal of the Asiatic Soc. of Bengal. [N.S., XVIII, 1922.} 
The following points are worthy of notice :— 
1. Since the heating circuit of the Coolidge is in connec- 
tion with the secondary circuit of the coil, the cells, ammeter and 
resistances used in the heating circuit are necessarily insulated 
from the earth. 
Consequently the heating circuit mercury cups D must be 
insulated from the clock itself and must in addition, be 
- separated from the nearest conductor on the clock by an insu- 
lator of length not less than the maximum alternative spark 
gap used with the coil. To this end, the arm which carries D 
is made of ebonite and is aboat 8” long. See Fig. 4 

_ 2. The wheel B revolves once in 15 seconds. Its energy 
is small and it is inadequate of itself to stop the motion of the 
axis 00’ by engaging direct with the wheel 8. Hence the 
necessity for making the catch N, actuated by B engage first 
with a wheel C which in turn engages with S, thus increasing | 
the mechanical advantage of B. ‘ 
_3. The periods to be adopted for the 2 stationary states. 
which periods depend on the conditions under which the 
Coolidge is required to work, can be altered by altering the 
arrangement of the teeth on the wheels A and B. Wheels of 
various type can be prepared and put on as required. 
eS Ne 

