LAW OF GRAVITATION. 225 



does not appear, then, that this hypothesis will 

 bear examination; although, for our purpose, 

 the argument would be rather strengthened than 

 weakened, if it could be established. 



6. Another theory of the cause of gravity, 

 which at one time excited considerable notice, 

 was that originally proposed by M. Le Sage, in 

 a memoir entitled, " Lucrece Newtonien," and 

 further illustrated by M. Prevost ; according to 

 which all space is occupied by currents of matter, 

 moving perpetually in straight lines, in all direc- 

 tions, with a vast velocity, and penetrating all 

 bodies. When two bodies are near each other, 

 they intercept the current which would flow in 

 the intermediate space if they were not there, 

 and thus receive a tendency towards each other 

 from the pressure of the currents on their farther 

 sides. Without examining further this curious 

 and ingenious hypothesis, we may make upon it 

 the same kind of observations as before ; that it 

 is perfectly gratuitous, except as a means of ex- 

 plaining the phenomena ; and that, if it were 

 proved, it would still remain to be shown what 

 necessity has caused the existence of these ttvo 

 kinds of matter ; the first kind being that which 

 is commonly called matter, and which alone 

 affects our senses, while it is inert as to any 

 tendency to motion ; the second kind being 

 something imperceptible to our senses, except 

 by the effects it produces on matter of the former 



