43 
FURNACES. 
sufficiently high with water, the fire being put in when the 
bottom was covered, and which engine was at work within 
the space of seventeen minutes from the time of its being 
filled with water. 
A similar boiler, placed on the usual construction, requir 
ed an hour and a quarter to raise the steam to the same 
degree of elasticity, as a boiler of this construction produced 
within eight minutes after it was filled above the flues, the 
fire being put in when the bottom was covered; and as it 
was a competition of skill, every possible exertion was used 
on both sides. 
This plan has been applied to the boiler of an engine for 
drawing coals, at Killingworth colliery, in Northumberland, 
which, on the usual plan, was inadequate to raise steam to 
do the work required, namely, to draw forty score of twenty 
peck corfs of coals, in fourteen hours, from a pit 120 fa 
thoms deep, although the engine, built by Messrs. Fenton, 
Murray, and Co. was well constructed, and kept in perfect 
order. The boiler is a round one, of thirteen feet diameter. 
without a flue through it, and the cylinder of the engine 
thirty inches diameter. Since Mr. Losh’s plan has been 
adopted, the engine performs the work with perfect 
case, although nothing out the smallest refuse coal is em 
ployed, and that only in the proportion of one-half of what 
was used before the improvement, without producing the 
desired effect. The engine will now work at its full power 
for nearly an hour after a fresh supply of fuel; whereas, on 
the former plan, it was requisite to give a fresh supply 
every ten minutes, or oftener. And although the effect of 
the heated air is so powerful, yet the fire itself is so mode 
rate, and the combustion of fuel so gradual and perfect, that 
no scars are formed ; and in consequence it is only found 
necessary to clean the grates once in two days, although the 
coals are of that quality which have a great tendency to 
vitrify at a high degree of heat. 
The only instructions necessary relative tofiring, or adding 
fresh supplies of fuel to boilers on this plan, are, to throw in 
much less at once than is usually done, to keep the bars well 
covered, but the fuel much thinner upon them, and the 
fires much brighter than in common furnaces ; to wait after 
adding coals to one furnace, till it has become bright, before 
a fresh supply is given to the other ; so that when one fire 
is at its highest degree of heat, the other is at its lowest, and 
thus the boiler may be kept continually at nearly an equal 
temperature ;—the advantages are evident.