84 Steam Engine* 
Its construction is very simple, and it performs its opera* 
tions very smoothly and effectually.* 
The preceding is a tolerably correct though brief ac- 
count of Savary’s, Newcomen’s, Watt’s and Cartwright’s 
engines : but it will in my opinion be of use to state un- 
der various modes of expression the same general facts^ 
that the distinctive characters, and the successive improve - 
ments of the principal steam engines may become fami- 
liar to the reader. The subject is new in this country, and 
is extremely important. I have already given all the pre- 
liminary knowledge relating to the power of steam that 
bears upon the question ; and I mean in the course of this 
and the next number to give all the knowledge necessary 
to a full understanding of the theory of the Steam Engine. 
The following brief history I extract from Professor Play- 
fair’s angry review of Gregory and Hornblower’s account 
of Steam engines ; but as I have nothing to do with the 
illiberal remarks of the latter, or the tart replies of 
the Professor, I insert no more than relates to the 
history of Mr, Watt’s discoveries and improvements, 
Edinb. Rev, for Jan, 1809, 
“ The fin-.t idea of the steam-engine is found in the writ- 
ings of that celebrated projector, the Marquis of Wor- 
cester, who, in the year 1663, published a small tract,, 
entitled, A Century pf Inventions,” consisting of short 
* Mr. Cartwright’s contrivance for preserving the parallel mo- 
tion of the piston-rod, at the same time that it communicates the 
rotatory motion to the fly, is very ingenious, and is therefore shewn 
in the plate fig. 3. where P is the top of the piston-rod, upon which 
is screwed a transverse bar B : to the ends of this bar, at equal 
distances from <he top of the piston-rod, are attached the two 
equal connecting rods H, H, which as the piston rises and falls 
turn the cranks and the two equal wheels \V, W ; these two equal 
wheels work into each other, and one of them drives the pinion C 
upon the saine axis as the fly-wheel O ; thus communicating the 
rotatory motion to the other parts of the machinery. (Hitherto 
frosp Hornblow^p’s account, T. C. 
