206 On the Measure of 
donc dans la premiere minute il ne peut avoir 
fermé qu’ a de mi chacun des deux ressorts, et 
a la fin de la seconde il les aura entiérement 
fermés tous deux, et sa force sera consumée.” 
Mr. Maclaurin has given, in his Treatise 
of Fluxions, page 431, some ingenious solu- 
tions of the problem where two or more bodies 
at rest are struck at the same instant by ano- 
ther body moving with a given velocity ina 
given direction. It is remarkable, however, 
that the consideration of the time was. omitted 
by him in the same way that it was omitted by 
M. Bernoulli; although the oversight of the 
latter had been pointed out by Mr. Robins 
fourteen years before Mr. Maclaurin published 
his solutions; which appear to be defective 
also in the following respect. . The resulting 
motions are first given on the supposition that 
the bodies are hard and non-elastic, and from 
these results are deduced the motions which are 
supposed to result from the collision of elastic 
bodies.—But M. D’Alembert has shown that, 
in all cases where the bodies which are struck 
are not. equal to each other, and similarly 
situated with respect to the direction of the 
striking body, the supposition of hard. bodies 
leads to erroneous results. with respect to 
