$32 GRAVITY AND LEVITY 



supposes that thetie is a fluid surrounding the 

 sunj which increases in density as it recedes 

 from the sun, and that u body put into this 

 fluid will be forced towards the sun by the dif- 

 ference of the .pressures on the opposite sides. 

 I. Bernoulli was dissatisfied with both these 

 hypotheses, and formed a system from the two, 

 (un juste milieu entre les deux m'a paru le plus 

 sur,) which he thinks will solve all the pheno- 

 mena. He supposes that there are two kinds 

 of vortices, one belonging to the sun, and the 

 other to the principal planets* He conceives 

 also, that there is a torrent which sets in con- 

 tinually from the extremity of the vortex to- 

 wards the centre, causing thereby a tendency 

 of all the bodies in the vortex towards that 

 point ; and thus he accounts for the gravitation 

 of the planets to the sun. He further supposes 

 that there are two sorts of matter ; one, per- 

 fectly fluid, without any elementary particles ; 

 without inertia ; and which gives no resistance 

 to bodies moving in it; the other formed of 

 corpuscles. These two matters are mixed to- 

 gether, and form the vortex. When the vortex 

 first began to revolve, the particles of the second 

 kind of matter, receded a little from the centre, 

 and formed a vortex of different densities, and 

 thus there remained a space about the centre 

 of the vortex, filled with the first matter only, 

 and this is the matter which forms the sun. The 



