ky Mol ue we 
On Mr. Cantwricut’s Invention for rendering the. P; ons 
of Steam Engines tight by metallic Parts, without Pack- 
hag or ‘Leather. 
To Me. TILLOCH. 
‘Sr R, % Richmond, Nev. 10, 1798. 
_ MY next door neighbour Mr. A. R. haying requefted 
Mr. Nicholfon* to give his opinion on Mr, Cartwright’s 
new method of packing fteam engines, and Mr. Nicholfon 
haying, in confequence, given a much lefs favourable judg- 
ment on the merits of the invention than that which ap- 
peared in the firft number of your Magazine, I fhall be 
much obliged if you will examine what he has advanced, 
and ftate in your next number, whether you think his objec- 
tions well founded, &c. 
Your conftant reader, 
No one will withhold from Mr. Nicholfon the tribute of 
praife, to which the numerous fervices he has rendered and 
ftill continues to render to feience fo juftly entitle him; nor 
avill it any way diminifh his acknowledged merit, fhould it 
be fhown that the opinion he has delivered on Mr. Cart- 
wright’s invention is founded on erroneous principles. Mr. 
N. has miftaken the conftruction of the pifton, deferibed 
another, and then endeavoured to fhow that triangles will 
not fit.a cylinder, nor a wafer occupy the diameter of a mill- 
ftone. Thefe are-not his words; but-they are the fair infer- 
ence.from his mode of expreffion, as we fhall fee* imme- 
diately, But firft we fhall briefly ftate how the. pifton js 
really conftruéted. Two metal rings are ground, by means 
well known to good mechanies, into the cylinder, fo as 40 fit 
it as perfeétly as art and induftry can make them—that is, 
fowell that no fteam can pafs between them and the cylinder : 
their upper and under fides are alfo ground perfectly flat, and, 
. * See Mr, Nicholfon’s Phil, Journ, vol. i's p, 264. 
‘ though 
