156 ON THE INTERACTION OF NATURAL FORCES. 



teaches, is the light of ignited gases ; and in their spectra we see 

 more especially those bright lines which are produced by ignited 

 hydrogen and by ignited nitrogen. "Within our system, also, 

 comets, the crowds of shooting stars, and the zodiacal light ex- 

 hibit distinct traces of matter dispersed like powder, which 

 moves, however, according to the law of gravitation, and is, at 

 all events, partially retarded by the larger bodies and incor- 

 porated in them. The latter undoubtedly happens with the 

 shooting stars and meteoric stones which come within the range 

 of our atmosphere. 



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 

 outermost planet, we should find that it would require several 

 millions of 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 centrifugal 

 force, which must act most energetically in the neighbourhood 

 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 themselves into 

 single planets, or, similar to the great original sphere, into 

 planets with satellites and rings, until finally the principal mass 

 condensed itself into the sun. With regard to the origin of 

 heat and light this theory originally gave no information. 



When the nebulous chaos first separated itself from other 

 fixed star masses it must not only have contained all kinds of 

 matter which was to constitute the future planetary system, 

 but also, in accordance with our new law, the whole store of 

 force which at a future time ought to unfold therein its wealth 

 of actions. Indeed, in this respect an immense dower was 

 bestowed in the shape of the general attraction of all the particles 

 for each other. This force, which on the earth exerts itself as 



