30 
Mr. Graham first referred to the results which he had ob- 
tained by evaporation from a series of small vessels of equal 
size, the fire being under the first and the flame bed alone 
passing under the others ; the evaporative power of the first 
w'as found to be equal to 100, the second to 27, the third to 
13, and the fourth to 8. A second set of experiments with 
larger vessels in the shape of boilers, corroborate these 
results. The third set of experiments w^ere with a view to 
exhibit the value of a supplementary boiler, as heating 
surface, placed under the most favorable circumstances ; the 
result showed an advantage of 15 per cent. 
Mr. Graham then detailed the results of a numerous set of 
experiments on evaporation on the large scale, with reference 
to engine boilers. 
Before beginning to register his results, the boilers in each 
case were reset, and put by careful and continuous experi- 
ment into what was found to be their best condition for 
giving the best working result, as regards the admission of 
air, the draught of the chimney, the size of the fire -jilace, 
the distance of the bars from the boiler, the thickness of the 
fire bars and of the fire itself, the form of the flame bed, 
flues, and bridges. In the case of one boiler, Mr. Graham 
stated that he believed for this purpose it had been altered at 
least thirty times. The experiments on the improved boilers 
were each of twelve hours’ duration, and they numbered from 
thirty to forty for each boiler. 
A perfect command was kept of the draught, which varied 
from *5 to *7 inches of pressure of water, and the temperature 
of the draught at the bottom of the chimney would generally 
melt lead, but never zinc. 
The conclusions which Mr. Graham has arrived at, arising 
out of his experiments, are the following : — 
1. That the boiler usually called the “ Butterley or Fish- 
mouth Boiler,” 25 feet in length and 7 feet diameter, under 
favorable, but what may be termed ordinary circumstances. 
