ON THE INTERACTION OF NATURAL FORCES. 177 



Let us make this addition to our assumption that, at 

 the commencement, the density of the nebulous matter 

 was a vanishing quantity as compared with the present 

 density of the sun and planets : we can then calculate 

 how much work has been performed by the condensation ; 

 we can further calculate how much of this work still exists 

 in the form of mechanical force, as attraction of the 

 planets towards the sun, and as vis viva of their motion, 

 and find by this how much of the force has been converted 

 into heat. 



The result of this calculation 1 is, that only about the 

 454th part of the original mechanical force remains as 

 such, and that the remainder, converted into heat, would 

 be sufficient to raise a mass of water equal to the sun and 

 planets taken together, not less than twenty-eight millions 

 of degrees of the Centigrade scale. For the sake of compa- 

 rison, I will mention that the highest temperature which 

 we can produce by the oxyhydrogen blowpipe, which is 

 sufficient to fuse and vaporise even platinum, and which 

 but few bodies can endure without melting, is estimated 

 at about 2,000 degrees. Of the action of a temperature 

 of twenty-eight millions of such degrees we can form no 

 notion. If the mass of our entire system were pure coal, 

 by the combustion of the whole of it only the 3,500th 

 part of the above quantity would be generated. This 

 is also clear, that such a great development of heat must 

 have presented the greatest obstacle to the speedy union 

 of the masses ; that the greater part of the heat must 

 have been diffused by radiation into space, before the 

 masses could form bodies possessing the present density 

 of the sun and planets, and that these bodies must once 

 have been in a state of fiery fluidity. This notion is cor- 

 roborated by the geological phenomena of our planet ; 

 and with regard to the other planetary bodies, the flat- 

 1 See note on page 193. 



