£39 > 
the steam engine. 
This engine consists of a large cylinder or barrel, in which 
is fitted a solid piston like that of the forcing pump. Steam 
is thus supplied from a large boiler, which in forcing up the 
piston, instantly opens a valve, through which cold water 
rushes, on the principle of the common pump. Otlier 
Steam is then introduced, which forces it down again, and 
drives the water out of the pipe with immense force. The 
steam then raises the jiiston again, and ag.aui makes it tall, 
by which alternate motion the grandest operations are per- 
formed. The action of the piston moves up and down a 
large beam j and this beam communicates to other machi- 
nery the power of 100 or 200 horses ! 
The power of some of the steam engines constructed by 
Messrs. Boulton and Watt, is thus described, as taken by 
actual experiment. An engine, having a cylinder of 31 
inches in diameter, and making 17 double strokes per 
minute, performs the work of 40 horses, working night and 
day, (for which lliree relays, or 120 horses, must be kept,) and 
burns 1 1 ,000 pounds of Staffordshire coal per day. A cylinder 
of 19 inches, making 25 strokes of 4 feet each per minute, 
performs the work of 12 horses, constandy labouring, ami 
burns 3,700 pounds of coals per day. These engines wdl 
raise more dian 20,000 cubic feet of water, 24 feet high 
for every hundred weight of good pit coal consumed by 
them. . , . 
The principle of Watts's improved engine, represented in 
die cut, is the same as die above, but the economy is still 
greater. The steam which is below the piston escapes into 
the condenser A, by the cock B, which is opened by the 
rod C, and at the same time the steam is admitted by die 
cock D into the upper part of the cylinder : when the 
piston has descended, the cocks E and F act in a siinilat 
manner in letting out the steam from above, and admitting 
it below the piston. The jet is supplied by die water of tlw 
cistern G, which is pumped up at H, from a reservoir : ic 
is drawn out, together with die air which is extricated from 
it, by the mr pump I, which dirows it into the cistern K., 
whence the pomp L raises it to the cistern M ) and U enteu 
