388 GRAVITATING FORCE. SECT. XXXVIII. 



with observation. Thus all matter is pervious to gravi- 

 tation, and is equally attracted by it. 



Gravitation is a feeble force, vastly inferior to electric 

 action, chemical affinity, and cohesion ; yet as far as 

 human knowledge extends, the intensity of gravitation 

 has never varied within the limits of the solar system ; 

 nor does even analogy lead us to expect that it should : 

 on the contrary, there is every reason to be assured that 

 the great laws of the universe are immutable, like their 

 Author. Not only the sun and planets, but the mi- 

 nutest particles, in all the varieties of their attractions 

 and repulsions, nay, even the imponderable matter of the 

 electric, galvanic, or magnetic fluid,- are all obedient to 

 permanent laws, though we may not be able in every case 

 to resolve their phenomena into general principles. Nor 

 can we suppose the structure of the globe alone to be 

 exempt from the universal fiat, though ages may pass 

 before the changes it has undergone, or that are now in 

 progress, can be referred to existing causes with the 

 same certainty with which the motions of the planets, 

 and all their periodic and secular variations, are refera- 

 ble to the law of gravitation. The traces of extreme 

 antiquity perpetually occurring to the geologist give that 

 information, as to the origin of things, in vain looked for 

 in the other parts of the universe. They date the be- 

 ginning of time with regard to our system ; since there 

 is ground to believe that the formation of the earth was 

 contemporaneous with that of the rest of the planets ; 

 but they show that creation is the work of Him with 

 whom " a thousand years are as one day, and one day 

 as a thousand years." 



In the work now brought to a conclusion, it has been 

 necessary to select from the whole circle of the sciences 

 a few of the most obvious of those proximate links which 

 connect them together, and to pass over innumerable 

 cases both of evident and occult alliance. Any one 

 branch traced through its ramifications would alone have 

 occupied a volume ; it is hoped, nevertheless, that the 

 view here given will suffice to show the extent to which 

 a consideration of the reciprocal influence of even a few 

 of these subjects may ultimately lead. It thus appears 

 thnt the theory of dynamics, founded upon terrestrial 



