Xt “for Steam Engines. A 284 
Uf othe pifton was made ofa Janger or Jefs diameter than 
the cylinder, and this difference was endeavoured to be acs 
comrodated by means of {prings, then Mr. N.’s objections , 
to this’ part would be well founded: in the former cafe the 
pieces of the rings would only touch the cylinder. at their 
extremities, and im the latter only in their middle—6 points 
only would be in contaét. But if we fuppofe the pifton rings 
of a larger'diameter [how came Mr. N. to think of fuch an 
abfurdity?]—let us at once fuppofe their diameter equal te 
that of the earth—each portion then would not differ fens 
fibly from a ftraight line. This however is only faying, that 
if Mr. Cartwright attempt to make a triangle fit a cylinder 
by means of. fprings, he will fail: fo he would alfo if he 
fhould. with half an inch endeavour to fill a mile. Mr. ©. 
does not propofe making any other: figure or dimenfion, fit 
his cylinder but its own; and has devifed a mean by which 
it muft, when once fitted, continue fo. 
-- Mr. Nicholfon is till more unfortunate: in his fecond: ob 
jection. “ When,” fays he, ‘a: great preffure, fuch, for 
exumple,-as the re-aétion of a colunm of 100 feet of water, 
comes tobe exerted upon the face of this apparatus; ‘the 
plates or pieces of thefe rings may be nnagined to be con- 
fined in a-vice. The preffure of fuch a column will amount 
tO) more than 40 pounds upon every fquare inch. “Whence 
we may conclude, either that they would not move satfall 
fiovitward, he means, againft the cylinder], or that the-foree 
ofthe fprings mutt be fuch as greatly to load the work with 
fridtion.””———If fuch a re-action could poffibly take place:in 
Mr: Cartwright’s fteam engine as would at one and the fume 
timeclay a force equal to 40:pounds per fquare inch.wpon both 
fedesof the piflon, it would be indeed in a vice; but not fuch 
a one as would caufe friction from the action of the fprings; 
for: this vice would keep the pifton at reft—it would neither 
afeend nor defeend. . But every one acquainted with mecha- 
nics mult, know, that, to make a well-conftructed fteamwen- 
‘ gine. 
