48 POPULAR LECTURES AND ADDRESSES. 



what the sun emits in 95 years. That is, indeed, a 

 prodigious amount of heat ; but just consider the 

 result if all the planetary bodies were to fall into 

 the sun. Take Jupiter with its enormous mass, 

 which, if falling into the sun, would in a few 

 moments cause an evolution of 32,240 years' heat. 

 Take them all together suppose all the planets 

 were falling into the sun the whole emission of 

 heat due to all the planets striking the sun, with 

 the velocities they would acquire in falling from 

 their present distances, would amount to some- 

 thing under 46,000 years' heat. We do not know 

 these figures very well. They may be wrong by 

 ten or twenty or thirty per cent., but that does not 

 influence much the kind of inference we draw from 

 them. Now, what a drop in the ocean is the 

 amount of energy of the motion of the planets, and 

 work to be done in them before they reach their 

 haven of rest, the sun, compared with what the 

 sun has emitted already ! I suppose all geologists 

 admit that the sun has shone more than 46,000 

 years ? Indeed, all consider it well established 

 that the sun has already, in geological periods, 



