103 
Steam Engine, 
into a motion of any kind which may suit his i^urpose. 
Savary’s engine could hardly admit of such a general ap- 
plication, and seems almost restricted to raising water. 
Newcomen’s engine was first offered to the public in 
1705. But many difficulties occurred in the execution 
of it, which were removed one by one ; and it was not 
till 1712, that the engine seemed to give confidence in its 
efficacy. 
The most exact and unremitting attention was requi- 
red, to open and shut the cocks precisely at the proper 
time ; for neglect might be ruinous to the machine, by 
the confined steam beating out the bottom of the cylinder, 
or allowing the piston to be wholly drawn out of it. Stops 
were contrived to prevent these accidents ; then strings 
were used to connect the handles of the cocks with tlie 
beam, so that they should be turned whenever it was in 
certain positions. These were gradually changed, and 
improved into detents and catches of different shapes ; at 
last, Mr. Beighton, a very ingenious and well informed 
artist, simplified the whole of these subordinate move- 
ments, and otherwise very much improved the machine. 
The greatest improvement that has since been made on 
Newcomen’s engine, has been in the manner of placing 
the boiler. Instead of placing it underneath the cylinder 
it is built at some distance from it, and sometimes in a 
separate building. 
About 1762, Mr. Watt began to turn his attention to 
this machine, which he has since brought to so great a de« 
gree of perfection. 
But before we explain Mr. Watt’s engines, itisneces- ‘ 
sary to premise a short account of the imperfections of 
the old steam-engines, and their causes. J| 
The steam or vapour which arises from water confined ip| 
in a close vessel, and heated a few degrees above the point 
at which it boils in the open air, becomes an elastic fluid. 
