106 Sullwan on the Revoluing Engine. 
Arr. X. Mr. Suurivan on the Revolving Engine ; in re- 
ply to Mr. DoouittLr.* 
TO PROFESSOR SILLIMAN. 
Sir, 
{ WAS so well aware of the adequacy of my descrip- 
tion of Morey’s Steam Engine in your second number, that 
i had already thought of offering a supplement, when you 
gave me an opportunity of reading the remarks of Mr. 
Doolittle, which | presume you will insert, preceding this 
further explanation. 
The invention was then quite in its infancy, and your 
American readers will require no apology for occupying a 
page of your Journal once more, with a subject perhaps in- 
teresting only as it relates to the developement of the re- 
sources of our country: this form of the engine being pe- 
culiarly adapted to canals and other inland navigation. .. 
_ Referring to the annexed plate and explanation, I will 
briefly attempt to answer the remarks of your correspon- 
dent. 
The objection that a part of the force is lost in producing 
a rotary motion, applies, I think with equal propriety to 
all engines communicating by the intervention of the crank 
—as in all of them it must be considered as a varying lever. 
By loss of force must be meant the difference between the 
effect it would produce were its action always at right an- 
gles to the crank, and its indirect action, as it revolves. 
Professor Playfair estimates this difference as 7 to 11— 
that is, a rotary motion is produced by the crank at the 
expense of ;‘,ths of the power which the engine would have, 
could it be exerted directly upon its object, or load. This 
estimate of loss relates to atmospheric engines. 
Notwithstanding this however, it was considered a great 
improvement when Mr. Watt introduced the crank. Jt gave 
the steam engine to many more useful purposes; though 
* Remark.—The temporary suspension of the Journal offered me an oppor- 
tunity of submitting Mr Doolittle’s remarks to Mr. Sullivan’s perusal, which 
gives these gentlemen the mutual advantage of having their pieces appear 
together, instead of coming out in different numbers.—Editor. 
