ON THE INTERACTION OF NATURAL FORCES. 155 



are also valid for other bodies than the earth. We will, there- 

 fore, make use of our law to glance over the household of the 

 universe with respect to the store of force, capable of action, 

 which it possesses. 



A number of singular peculiarities in the structure of our 

 planetary system indicate that it was once a connected mass, 

 with a uniform motion of rotation. Without such an assump- 

 tion it is impossible to explain why all the planets move in the 

 same direction round the sun, why they all rotate in the same 

 direction round their axes, why the planes of their orbits and 

 those of their satellites and rings all nearly coincide, why all 

 their orbits differ but little from circles, and much besides. 

 From these remaining indications of a former state astronomers 

 have shaped an hypothesis regarding the formation of our 

 planetary system, which, although from the nature of the case 

 it must ever remain an hypothesis, still in its special traits is so 

 well supported by analogy, that it certainly deserves our atten- 

 tion ; and the more so, as this notion in our own home, and 

 within the walls of this town, 1 first found utterance. It was 

 Kant who, feeling great interest in the physical description of 

 the earth and the planetary system, undertook the labour of 

 studying the works of Newton ; and, as an evidence of the depth 

 to which he had penetrated 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 inde- 

 pendent 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 now occupied by our 

 system far beyond the limits of Neptune, our most distant 

 planet. Even now we discern in distant regions of the firma- 

 ment nebulous patches the light of which, as spectrum analysis 

 1 Koriigsberg. 



