XXXII. An Invefllgathn of the Principles of progrejfve 
•end rotatory Motion . By the Rev. S. Vince, A. M. of 
Sidney College, Cambridge. Communicated by George 
Atwood, A. M. F. R. S. 
HE communication of motion from impact is 
well known to conftitute a conliderable part of 
that branch of natural philofophv called mechanics ; 
and as all our enquiries therein are directed, either 
to affift us in thofe operations w'hich add to the con- 
veniences of life, or to explain, for the fatisfadion 
of the mind, thofe changes which we daily fee arife 
from the effeds of bodies on each other, it might na- 
turally have been expected that the attention of philo- 
fophers would have been engaged, fir ft in the invefti- 
gation of fuch cafes as moft frequently occur from the 
accidental adion of one body on another, before they 
had proceeded to others lefs obvious. A little con- 
fideration will ‘convince any one how feldom it hap- 
pens, in the collifion of two bodies, that their centers 
Kead June 15, 1780. 
of 
