I 95° 1 
XLIII. Account of the Advantages of a newly-invented 
Machine much varied in its Effects, and very ufeful 
for determining the perfect Proportion between different 
Moveables a&ing by Levers and Wheel . and Pinion. 
By Mr. Le Gerf, Watch-maker at Geneva ; Commu- 
nicated by Lord Vifcount Mahon, F. RS 
A VI NG received From Mr. le cere, watch-maker 
at Geneva, two inftruments of his invention, with 
the annexed paper ; and being defired by him to prefent 
them to the Royal Society, I take the liberty of fending 
them to you, as fecretary of that learned Body. I have 
perufed this intCrefting treatife, which contains fome 
new and valuable thoughts upon the relative lize of 
wheels and pinions working together; and this being 
one of the things of the mod; general ufe, with refpeft 
to the improvement and eafy execution of clocks, 
Read July 9, 177,9. 
TO SAMUEL HORSLEY, LL.D. S. R. S 
$ I R 
Harley Street, 
March 19, 1778. 
watcher, 
