548 Mr. vince’s Invejligation of the 
bodies after impadt in a manner fomewhat different, but: 
has rendered it much more intricate by a fluxional cal- 
culus. To any one, however, who attentively confiders 
the fubject, the theory mutt ftill appear to be extreme- 
ly imperfedt, as, independent of principles not more 
felf-evident than the propofitions they are intended to 
demonftrate, which both 1. and d. Bernoulli have af- 
lumed in their inveftigations,a great variety of other cir- 
cumftances equally interefting naturally arife in an enquiry 
into this matter, circumftances abfolutely necelfary to- 
wards underftanding the principles of the motion of the 
bodies after impadf. This induced me to conlider the 
fubjedt with fome attention, and prefuming that 1 have 
not been altogether unfuccefsful in my endeavours to 
render the theory more perfedt, I determined to lay the 
refult of my enquiries before the Royal Society. I 
thought it expedient, for the fake of perfpicuity, to di- 
vide the whole into diftindt Proportions ; and as the 
moil fimple cafes are belt underftood, I have firft con- 
fidered the cafe of the adtion of a body on a lever hav- 
ing a corpufcle at each end : and I was the more in- 
duced to treat the fubjedt in this manner, as moft of 
the principles can be immediately applied to any num- 
ber of corpufcles, in confequence of which the gene- 
ral inveftigations are rendered more eafy and fatisfac- 
tory. 
PROP 
