33 8 Mr . smeaton’s Fundamental Principles 
IT is univerfally acknowledged, that the firft fimple prin- 
ciples of fcience cannot be too critically examined, in or 
der to their being firmly eftablifhed ; more efpecially thofe 
which relate to the practical and operative parts cf mecha- 
nics, upon which much of the aeftive bufmefs of mankind 
depends. A fentiment of this kind ocCafioned my trad! upon 
Mechanic Power , which was publifhed in the Philofophical 
Tran factions, vol. LXVI. for the year 1776. What I have now 
to offer was intended as a lupplement thereto, and the expe- 
riments were then, in part, tried ; but the completion thereof 
was deferred at that time, partly from want of leifure ; partly 
to avoid too great a length of the paper itfelf ; and partly to 
avoid the bringing forward too many points at once. My 
prefent purpofe is to fhew, that the true dodhine of the col - 
upon of bodies hangs as it were upon the fame hook, as the 
dodlrine of the gradual generation of motion from reft, conli- 
dered in that paper ; that is, that whether bodies are put into 
gradual motion, and uniformly accelerated from reft to any 
given velocity ; or are put in motion, in an inftantaneous 
manner, when bodies of any kind ftrike one another; the 
motion, or fum of the motions produced, has the fame relation 
to mechanic power therein defined, which is. neceftary to pro- 
duce the motion defined. To prove this, and at the fame 
time to fhew forne capital rniftakes in principle, which 
have been affumed as indifputable truths by men of great learn- 
ing, is the reafon of my now purfiling the fame fubjedh 
I do not mean to point out the particular rniftakes which 
have been made by particular men, as that would lead me into 
too great a length : 1 filial 1 therefore content myfelf with ob- 
ferving, that the laws of collifion, which have been invefti- 
gated by mathematical philofophers, are principally of three 
kinds ; viz. thofe relating to bodies perfectly elajlic ; to bodies 
perfectly 
