158 ON THE INTERACTION OF NATURAL FORCES. 



not less than twenty-eight millions of degrees of the Centigrade 

 scale. For the sake of comparison, 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 esti- 

 mated 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 com- 

 bustion 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 corroborated 

 by the geological phenomena of our planet ; and with regard 

 to the other planetary bodies, the flattened form of the sphere, 

 which is the form of equilibrium of a fluid mass, is indicative 

 of a former state of fluidity. If I thus permit an immense 

 quantity of heat to disappear without compensation from our 

 system, the principle of the conservation of force is not thereby 

 invaded. Certainly for our planet it is lost, but not for the 

 universe. It has proceeded outwards, and daily proceeds out- 

 wards into infinite space ; and we know not whether the medium 

 which transmits the undulations of light and heat possesses an 

 end where the rays must return, or whether they eternally 

 pursue their way through infinitude. 



The store of force at present possessed by our system is also 

 equivalent to immense quantities of heat. If our earth were 

 by a sudden shock brought to rest in her orbit which is not to 

 be feared in the existing arrangement of our system by such 

 a shock a quantity of heat would be generated equal to that 

 produced by the combustion of fourteen such earths of solid 

 coal. Making the most unfavourable assumption as to its capa- 

 city for heat that is, placing it equal to that of water the 

 mass of the earth would thereby be heated 11,200 degrees; it 



