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linear Motion in the encompafllng Matter; this 
Zvlotion muft therefore be turned afide, and will by 
this means become circular. 
But why fliould the encompalling Matter, which is 
at Reft, be an Obftacle to the redilinear Motion ? Be- 
caufc, fay they, it happens to be in the Line defcribed 
by the Particle, on which Motion is fuppofed to be 
imprinted. But this very Reafon would alfo prove, 
that the Body fuppofed to be in Motion could not 
circulate round a Centre at a Diftance from it ; be- 
caufe it would conftantly meet with Matter at Reft 
in the Sides of the Polygon which it was to have 
defcribed. 
In a Word, it is a received Principle, that a Body 
which moves in a homogeneous Medium, never quits 
the Line of its firft Dire6fion : It does not refradt, or 
deviate on one Side or the other of this Diredion, 
except when it pafles from an eafier into a more 
difficult Medium, or from a denfer into a lefs denfe 
Medium : and even then its Dircdion muft be oblique 
on the Surface of this Medium. 
Now, the Body in Queftion would move in a 
Medium intirely homogeneous ; feeing all the created 
Matter is fuppofed to be fo, and that all but one Par- 
ticle of this Matter is at Reft. It is moreover evident, 
that as all the Matter is uniform, every Diredion, of 
what kind foever, of a Body which moves in the 
midft of this Matter, will be perpendicular to the 
Surface which correfponds to it; as is demonftrated 
in Mechanics. The fuppofed Mobile will therefore 
always move in the Line of its firft Diredion, until 
it has communicated all its Force ; or rather it will 
remain 
