STEAM ENGINE. 
realize the noble marquis’s project : he made 
Uie pressure of steam act immediately on 
the surface of water contained in a close 
vessel, and the water was forced, by the 
elasticity of the steam, to ascend through a 
pipe. The objection to this was the great 
heat required for raising water to any con- 
sideiable lieiaht : and also the waste of 
steam by its coming in contact with the 
cold water in the receiver, the surfaces of 
which required to be heated to its own tenw 
peratiire, before the water could be expell- 
ed. Tl'.cse inconveniences were in a great 
measure, avoided in Newcomen’s engine, 
where the steam was gradually introduced 
into a cylinder, and suddenly condensed by 
a jet of water, so that the piston was forced 
down with great violence by the pressure 
of the atmosphere, which produced the ef- 
fective stroke : this etfect was, however, 
partly employed in raising a counterpoise, 
which descended upon tiie readmission of 
the steam, and worked a forcing pumii in 
its return, when water was to be raised. 
Engines on this principle were commonly 
used in this country, till the improvements on 
>^hom were introdimed by Mr. Watt, to 
whom the public, in this hiisiness, is more 
indebted than to any other person. Tiie 
engines constructed by this gentleman are 
said to save three-fourths of the fuel that 
was used in the best constructed engines of 
Newcomen, with the waste of only one 
fourth of the steam. He has contrived to 
observe an uniform beat in the cylinder of 
his engines, by suffering no cold water to 
touch it, and by protecting it from the air, 
or other cold bodies, by a so; rounding case 
tilled with steam, or with hot air, or water, 
and by coating it over with substances that 
conduct the heat very slowly and imperfect- 
ly. He makes his vacuum to approach 
nearly in excellence to that of a barometer, 
by condensing the steam in a separate ves- 
sel, called the condenser, which may be 
cooled at pleasure, vvithout cooling the cy- 
linder, either by an injection of cold water, 
or by surrounding the condenser with it. 
He extracts the injection water, and de- 
tached air, from the cylinder, or condenser, 
by pumps, which are worked by the engine 
itself. As the entrance of air into the 
cylinder would stop, or very much impede, 
the operation of the engines, and as it is 
almost impossible to expect such pistons to 
be absolutely air-tight, a stream of water 
used to be kept running on the piston, to 
prevent the entry of the air, as the lighter 
fluid could not descend through the hea- 
vier : this mode, which w’as not injurious to 
the engines on the old construction, could 
not fail to injure the modern ones of Mr, ' 
Watt. He therefore makes his pistons more 
accurately ; and tlie outer cylinder, having a 
lid, which covers it, the steam is introduced 
above the piston, and when a vacnnra is 
produced under it, acts upon it by its elasti- 
city, as the atmosphere does upon common 
engines by its gravity. This method of 
working efl’ectually excludes the air from 
the inner cylinder, and gives the advantage 
of adding to the power, by increasing the 
elasticity of the steam. We shall endea- 
vour to give our readers an idea of the 
manner in which Mr. ATatt’s engine works, 
and then present them with an accurate 
description, accompanied with engravings 
of one, to which our draftsman has had ac- 
cess for the purpose. 
The cylinder in Mr. Watt’s engines is 
ver y accurately bored, and surrounded at a 
small distance with another (-ylinder fur- 
nished with a bottom and lid. The intei> 
val between lire cylinders communicates 
with the boilers by a large pipe, open at 
both ends, so that it is always filled with 
steam, and thereby keeps the inner cylinder 
at the same temperature as that of the 
steam, and prevents any condensation. The 
inner cylinder has a bottom and piston as 
usual; and as it does not reach q«iite up to 
the lid of the outer cylinder, Ihcsteam in the 
interval has always free access to the upper 
side of the piston. The lid of the outer 
cylinder Las a hole in its middle; and the 
piston rod, which is truly cylindrical, moves 
up and down through that hole, which is 
kept steam-tight by a collar of oakum screw'- 
ed down upon it. At the bottom of the 
inner cylinder there are two regulating 
valves, one of which admits tlie steam to 
pass from the interval into the inner cylin- 
der below the piston, or slmts it out at 
pleasure : the other opens or shuts the end 
of a pipe, which leads to the condenser. 
The condenser consists of one or more 
pumps, furnished with clacks and buckets, 
which are worked by chains fastened to the 
great working beam of the engine. Tim pipe 
whioh comes from the cylinder is joined to 
the bottom of these pumps, and the whole 
condenser stands imraersed in a cistern of 
cold water, supplied by the engine. The- 
place of the cistern is either within the 
house or under the floor, between the cylin- 
der and the lever wall; or without the 
house, between that wall and the engine 
shaft. The condenser being er^hausted of 
