385 
Steam Engine. 
the piston ; and when the force of the steam is taken off 
by copidensation, the piston descends forcing the oil back 
into its former situation, and so on alternately. The oil 
of course is kept hot. In this way any escape of air 
among the steam to re-act against the motion of the pis« 
ton is doubtless prevented * but I have not been able to 
procure the specification at length, and therefore cannot 
pretend to accuracy concerning it. 
His boilers are of a new, and, as I think, a greatly im- 
proved form. Of this improvement I have given a de- 
scription and a plate. 
All these improvements are open to our own engineers. 
The time is now come, when a civiU engineer will be in 
general demand, and will meet with the success in point 
of fi')rtune, and the respect in point of situation in society, 
which the able men of this description are sure to find in 
Great Britain. The three great requisites of a civil en- 
gineer, are first a profound knowledge of mathematics, 
and an habitual facility of applying mathematical princi- 
ples and calculations to mechanics and machinery. Se* 
condly, a full knowledge of the modern science of che- 
mistry. Thirdly, an habitual facility in drawing and 
designing with neatness and accuracy. To these should 
be added, actual observation and study of the principal 
machines in use and their application. 
I have given Mr. Oliver Evans's description of his 
steam engine, but for want of his patent- specification, I 
am not able to point out precisely, what part of it he 
claims as his peculiar invention. I shall be glad to in- 
sert such a precise specification of his claim when I am 
enabled so to do. 
For the present. I conclude the article of Sts ah En- 
gines. 
