Examination of the Theory of a Resisting Medium. 3 
Through the long period of time embraced by these references, 
we see the existence of this fluid matter every where accredited ; 
yet so vague and indefinite do all ideas respecting it appear to have 
been, that rigid investigation of its character or necessity seems to 
have been quite neglected; and even its practical utility, so far as 
we know, was but very limitedly considered. But we are now to 
enter upon a new era, and that a very important one, in the history 
of this fluid; for we are to see it elevated from the subordinate sta- 
tion hitherto assigned it, to that of a primary agent in carrying out 
the great motions of the universe. This application was the off- 
spring of the genius of Descartes. The conception was a sublime 
one which dared to identify the law of the general. movement of 
the universe, with that of the movement of terrestrial bodies: and 
this is due to Descartes. His vortices are a bad explanation of 
gravity and of the system of the world, but they are mechanical. 
He discovered that the same mechanism moved bodies in the celes- 
tial spaces and at the surface of the earth; and if he was not able 
to seize this mechanism, we should not forget that this new and 
sublime thought was of his conception.(8) According to this phi- 
losopher “ matter, possessed only of the properties of extension, im- 
penetrability and inertia, was supposed to fill all space, and its parts, 
both great and small, to be endued with motion in an infinite variety 
of directions. From the combination of these, the rectilineal motion 
of the parts became impossible; the atoms or particles of matter 
were continually diverted from the lines in which they had begun 
to move; so that circular motion and centrifugal force originated 
from their action on one another. Thus matter came to be formed 
into a multitude of vortices, differing in extent, in velocity and den- 
sity; the more subtile parts constituting the real vortex, in which 
the denser bodies float, and by which they are pressed, though not 
equally, on all sides. Thus the universe consists of a multitude of 
vortices, which limit and circumscribe one another. ‘The earth 
and the planets are bodies carried round in the great vortex of the 
solar system; and by the pressure of the subtile matter, which cir- 
culates with great rapidity, and great centrifugal force, the denser 
bodies, which have less rapidity, and less centrifugal force, are 
forced down toward the sun, the centre of the vortex. In like 
(8) Bailly, Histoire de ?Astronomie Ancienne, Discours Preliminaire; and 
Playfair on Mathematical and Physical Science. 
