^'"^Hfi Autk^r tkfe EiTay tells as ;totfcfelf, thitt it 
Jl^ was de%ned to facilitate the explicating of the 
Dottrine of occult qualities; and premifes thispoftula- 
turn in order to the demonftrations that follow, vt^.th^t 
we are not to confider bodys as fo many lumpsof matter 
that differ oaly in bulk, and Ihapej but rather as bodys 
of peculiar internal textures; on account of which they 
mutt be confidered as Engines, whofe operations being 
furthered by the mechanifm of the body wrought dn, 
and the relation other bodys have to it, a great part of 
the effe^ is due to the adion of one part of the body it 
felf that, is wrought on, upon another, affift^d by the 
concutrence of the Neighbouring - bodys. Hence he 
takes notice of the chief caufes upon whole account men 
are wont to over-look or under value, the efficacy of lo- 
cal Motions which are either unheeded, or thought lan- 
guid. The firft thing overlooked is the efficacy of the 
celerity of fmall bodys moving, through a fmall ipacej 
how^reat this is he illuftrates by confidering the power - 
full effeds of Bullets ; the great incalefcence caufed by 
the brisk Motioa in turning of Metals, as Steel and Brafs^ 
the fragments of which are often fo heated, asnotonely 
to offend the Ey-lids; but even to blifter the hands of 
the workmen : vitrification itfelf being produced by the 
common ftriking fire between a Flint and SteeK Neither 
arc fluid bodys uncapable of making impreflSons on folid 
ones, witnefs Sunbeams in the focus of a Burning-Glafs; 
the Flame of a lamp; and even the Air in a good Wind- 
Gun. Though we are in the fecond place too apt to 
think, the foftnefs of fluid bodys, and their infenfible 
Motion may hindcif them from thofe effects. But to 
fliew 
