88 THE LIMITATIONS OF SCIENCE 



was sufficiently great to separate them from each other, 

 and was therefore great enough to knock off their 

 angular edges and corners because of the concussions 

 of their future impacts. The result of such a constant 

 attrition is well known to be that the body approaches 

 the figure of a sphere, just as the pebble on the seashore 

 becomes round from the grinding of the waves and its 

 fellows. 



This action gives rise to three forrns of matter which 

 constitute the universe, and whose various forms of ag- 

 gregation and proportions of mixture, with their re- 

 sulting varieties of motion, account for all the diversi- 

 fied kinds and attributes of matter and space. 



The first kind of matter is the cosmic dust of attri- 

 tion or the little fragments resulting from the above 

 mentioned collisions. They are excessively small and 

 have acquired enormous velocities, because the larger 

 particles, from which they were split off, have con- 

 strained them to move faster than themselves through 

 the narrow and tortuous paths formed by their inter- 

 stices, just as air in a whistle moves the faster, the 

 smaller the orifice from which it issues. They are 

 also so numerous, so various in size, and so irregular 

 of shape, that there are always sufficient of them ready 

 to hand to fill exactly any space which might other- 

 wise be left vacuous by the arrangement and motion of 

 their parent sphericules. 



The second elementary kind includes all the rest of 



