ae ta. -—--~ * 
OF COAL AND RATE OF EVAPORATION. 19 
and loose pulley, the direction of which was entrusted to 
the stoker, while the levels of the water in the boiler, 
and other circumstances at the beginning and end of 
each experiment were registered by another person. The 
drawing scarcely gives a proper idea of the mode by which 
the water was conveyed round and into the boiler. 
I shall now give an account of the results obtained by me 
with the four different shapes of boilers in most common 
use in this neighbourhood. I should remark that before 
beginning to register results, the boilers in each case were 
re-set, and placed, by careful and continuous experiments, 
into what was found, to the best of my judgment, to be 
their condition for giving the best working result. The 
boilers were, further, always amply protected by coverings 
from loss of heat by radiation. The experiments of the 
present series were each of twelve hours duration. They 
commenced at 6 a.m. and terminated at 6 p.m., except those 
performed on Saturdays, which lasted from 6 a.m. to 1 p.m. 
It was also the practice to commence and end with the 
steam at, as nearly as possible, 7 lbs. of pressure. 
As each experiment of importance was carried on day by 
day for four or six weeks, and often repeated under vary- 
ing circumstances at different times of the year, also with 
various boilers, with coals of various kinds, aud different 
stokers, the experiments altogether occupied the better part 
of several years. At first the disturbing circumstances 
were found very perplexing, as they led to variations in the 
results which at the time could not be explained; but in 
proportion as these circumstances became known and were 
reduced in number, it became possible to proceed with 
more satisfaction and precision. The coals used in these 
experiments were the usual Worsley qualities, except in 
the case of the experiments made with the cylindrical 
boiler, described under the head IX. Series of Experi- 
ments, where Dukinfield coal was used. I had, however, 
