PHYSICAL ann LITERARY. 129 
Many fruitlefs attempts have formerly 
_ been made to explain all the phenomena of 
 pature, on mechanical principles alone. But 
itis exceedingly furprifing, that, in the prefent 
age, fo eminent an aftronomer as M. Mau- 
periuis™ (hould again revive exploded notions; 
and fugeeft, that the planets may poflibly be 
retained in their orbits, by the motion of a 
Circumambient fluid, as an ultimate caufe. 
"There is nothing more demonftrably certain, 
than that gravity cannot arife from the pref- 
fure of a whirlpool, or vortex of a denfe flu- 
id, once put in motion, and continuing to 
move round of itfelf, as M. Des Cartes ima- 
gined. And it is needlefs at prefent to exa- 
mine, whether it can be better explained by 
means of a rare elaftic ether. If Sir Tfaac 
Newton endeavours in that manner to account 
for gravity, the attraction of cohefion, the 
reflexion and refraction of light, &c, it is 
— only with a view to point out {ome more ge- 
~neral mechanical caufe, upon which all thefe 
" powers may poflibly depend. He never could 
believe that bis aether was poffeffed of a real 
_aétivity of its own. The elafticity of that 
a R. fluid 
> 
* Co/mologie. 
