go ESSAYS ann OBSERVATIONS 
From the experiment of Mr Poleni we’ 
learn, That fpheres of equal diameters falling 
upon foft clay, make equal impreffions, when 
the products of the quantities of matter into 
the heights from which they fall, are equal ; 
that is, when the quantities of matter multi- 
plied by the fquares of the velocities are e- 
qual. As it is much eafier to determine 
when two imprefiions are equal, than when 
they differ in any proportion of magnitude ; ~ 
the velocities of the different bodies in this 
experiment, are fo adjufted, in refpect of the 
quantities of matter, as that the impreffions 
may be equal. But, from thence we con- 
clude, that fuch impreflions are always as the 
quantities of matter and fquares of the velo- 
cities conjointly; and confequently, when 
the quantities of matter are equal, the im- 
preffions will be as the fquares of the veloci- 
ties. The fame experiment may be fhewn 
perhaps ina more fimple manner, by making 
pendulums of different quantities of matter, 
to ftrike with different velocities upon a 
fmooth furface of foft clay; the velocities 
being always affigned by help of a graduated 
arch, as is done in the common experiments 
of the collifion of bodies. In this manner, 
likewife, , 
