• Ls ] 
be n : m : : a : 2 £, as appears by taking the fluxion 
of J 1 '- r ; b r~ — o, and reducing the equation in 
the manner above. Whence the load to be raifed 
for the greateft effed of a fteam-engine, if the Inertia 
of the materials compoflng its working parts be put 
out of the queftion, will be juft half of what is Suf- 
ficient to balance the atmofphere, whether the Bra- 
chia of the lever be equal or not. 
Permit me now to trouble you with two or three 
remarks on what I formerly laid before you concern- 
ing the proportion of the cylinders. And, ift, in all 
values of the Brachia, with regard to their lengths, 
and all values of », the exprefiion for 
the time of a ftroke, when m is a weight, is the ge- 
neral exprefiion to be ufed for the time. 2dly, m 
being confidered as a fpring, the time of a ftroke 
7 ; and then if, according to what I 
m a — nb 1 ° 
have there direded, a be taken variable, and m the 
reciprocal of a , the advantages to be gained by the 
breadth of the cylinder can only arile from a diminu- 
tion of fridion, and from the matter in the Beam 5 
for, the exprefiion J -~~~ b becomes conftant, and 
thence the ftrokes are ifochronal. I might, further- 
more, proceed to examine into thefe advantages, more 
explicitly than is there done, upon the principles laid 
down, when m is a weight. But many particulars 
(fuch as the form of the Brachia and various appen- 
dages, with their quantities of matter and centers of 
gyration) 
