ORIGIN OF THE NEBULAR HYPOTHESIS. 231 



system, undertook the labour of studying the works of New- 

 ton, and as an evidence of the depth to which he had pene- 

 trated into the fundamental ideas of Newton, seized the notion 

 that the same attractive force of all ponderable matter which 

 now supports the motion of the planets, must also aforetime 

 have been able to form from matter loosely scattered in space 

 the planetary system. Afterwards, and independent of Kant, 

 Laplace, the great author of the Mecanique Celeste, laid hold 

 of the same thought, and introduced it among astronomers. 



The commencement of our planetary system, including 

 the sun, must, according to this, be regarded as an immense 

 nebulous mass which filled the portion of space which is now 

 occupied by our system, far beyond the limits of Neptune, 

 our most distant planet. Even now we perhaps see similar 

 masses in the distant regions of the firmament, as patches of 

 nebulas, and nebulous stars ; within our system also, comets, 

 the zodiacal light, the corona of the sun during a total eclipse, 

 exhibit remnants of a nebulous substance, which is so thin 

 that the light of the stars passes through it unenfeebled and 

 unrefracted. If we calculate the density of the mass of our 

 planetary system, according to the above assumption, for the 

 time when it was a nebulous sphere, which reached to the 

 path of the outmost planet, we should find that it would 

 require several cubic miles of such matter to weigh a single 

 grain. 



The general attractive force of all matter must, however, 

 impel these masses to approach each other, and to condense, 

 so that the nebulous sphere became incessantly smaller, by 

 which, according to mechanical laws, a motion of rotation 

 originally slow, and the existence of which must be assumed, 

 would gradually become quicker and quicker. By the cen- 

 trifugal force which must act most energetically in the neigh- 

 bourhood of the equator of the nebulous sphere, masses 

 could from time to time be torn away, which afterwards would 

 continue their courses separate from the main mass, forming 



