ang Mr. Cartwright’s Piffor. 
gine work, the preffure muft aé only.on one fide of the piftort 
at atime! 
In Mr. C.’s engine, the pifton is not intended to adapt it~ 
felf to inequalities in the cylinder; all inequalities are firft 
removed. In the working, the pifton afcends in vacuo, by 
the momentum communicated to the fly-wheel; therefore 
at that time ¢here is no preffure on either the upper or under 
fede of the pifton, and the {prings are in full aétion, prefling, 
lightly and uniformly, the whole circumference of the rings 
againit the cylinder, When the pifton reaches the top of 
the cylinder it raifes the fteam valve; and the fteam then 
entering acts only on the upper furface of the pifion, and 
forces it to defcend ; but, condenfation having taken place 
below the pifton, the whole under {pace is a vacuum, more 
or lefs perfect, and therefore there can be no re-acting 
power to perform the office of the vice! : 
Whether this contrivance will anfwer for pumps and 
other hydraulic apparatus, is not the prefent enquiry. It 
will be time enough to give an opinion on that point when 
we fee what mode of conftruction may be ufed in fuch an 
application of the invention. A..T. 
ERRATUM. 
In our laft Number, page 111, in the Recipe for preparing 
oxygenated Ointment, for Nitric Acid 3ij read 3ij. 
