MOVING FORCB. 
255 
it would have been zealously cultivated, and miglit have proved Casps of ditS- 
higlily interesting to mathematicians, as well as of essential joctiim-s of 
service to practical men, in explaining those variations of force, t'*'*^^* 
to the useful application of which their operations are chiefly 
directed. 
If we wish to trace the history of this measure of force 
to its origin, we must go back to Galileo. It was first 
demonstrated by him, that the spaces described by heavy 
bodies, from the beginning of their descent, are as the 
squares of the times, and as the squares of the velocities 
acquired in those spaces ; and he first distinctly explained all 
the phenomena of the motions of bodies uniformly acce- 
lerated or retarded by constant forces in their simple, and like- 
wise in their compound actions. The law of continuity ap- 
pears also to have originated with him. It is most extraordi- 
ri.Try, that both Mr. Robins, and Mr. Maclaurin have spoken 
of this law with great disapprobation* j and that, although 
it had been distinctly stated by Galileo, nearly a hundred years 
before the time they wrote against it, they considered it as 
a new and a visionary doctrine produceil by Leibnitz or his 
followen, forthe purpose of controverting the arguments which 
had been produced in support of the supposed collision of hard 
bodies. Galileo appears to have been fully sensible of the im- 
portance of the law of continuity, and to have been aware, also, 
of the objections which might probably be brought ag.ninst it. 
In his first dialogue he supposes a difficulty to arise in the mind 
of one of his speakers, who states it thus. “ Id est, quod non 
satis capio, cur necesse sit, ut mobile quietem deserens, et 
motum inclinatione naturali sublens, omnes transeat gradus 
praecedentis tarditalis, qui inter queracunque certum velocitatis 
gradum, et statum quietis, inteijecti sunt To which the fol- 
lowing remarkable answer is given : “Non dixi, nec ausim 
dicere, naturae ac Deo impossibile esse, velocitatem illam quam 
dicis, immediate conferre : sed hoc affirmo, quod id natura de 
facto non praestet. Si vero praestarct, ea operatio naturae cursum 
• Rollins’ Tracts, p. 171-5.— Maclanrin’s .Accotmt of Sir Isaac New- 
tou's discoveries, p. 92-3- 
exce- 
