18 MR. JOHN GRAHAM ON CONSUMPTION 
consumed. I have no results to show what the effect 
might be if the supplementary heating apparatus had been 
applied to a boiler capable of yielding itself a larger result. 
IV. Series or EXPERIMENTS. 
The next set of experiments was made for the purpose of 
ascertaining the evaporative power of engine boilers of va- 
rious shapes and of large dimensions. 
In order to do this I found it necessary to contrive a 
simple water meter capable of registering the supply of 
water to the boiler with accuracy. This machine is exhi- 
bited in the accompanying figure. 
Fig. 6. Water Meter. 
This meter worked with perfect accuracy for several 
years, as was ascertained by occasionally checking its 
registered indications by means of a water cistern of 
known capacity attached. The registering apparatus was 
similar in construction to that used in gas meters, and was 
attached to one end of the axle. The interior part of this 
apparatus, which conveyed the water into the boiler, was 
not unlike a large “ greasing tap.” It was driven by a fast 
