286 DISCUSSIONS IN COSMOLOGY. 



tion the magnitude of the stellar universe, the difference 

 between a motion of 202 miles per second, and one of 

 1700 miles to a great extent disappears, and the one 

 velocity becomes about as probable as the other. If 

 the original velocity was 676 per second, the total 

 amount of heat generated would suffice for 200 million 

 years at the present rate of radiation. 



On former occasions* I expressed it as my opinion 

 that the total quantity of heat possessed by the sun 

 could not probably exceed 100 million years' heat. 

 But if we admit that the heat was derived from 

 Motion in Space, there really does not seem any reason 

 why it may not be double or quadruple that amount. 



It will be asked, Where did the two bodies get their 

 motion ? It may as well, however, be asked, Where 

 did they get their existence ? It is just as easy to 

 conceive that they always existed in motion as to 

 conceive that they always existed at rest. In fact, 

 this is the only way in which energy can remain in a 

 body without dissipation into Space. Under other 

 forms a certain amount of the energy is constantly 

 being transformed into heat which never can be re- 

 transformed back again, but is dissipated into Space as 

 radiant heat. But a body moving in void stellar space 

 will, unless a collision takes place, retain its energy in 

 the form of motion untransformed for ever. 



It will perhaps be urged as an objection that we have 

 no experience of bodies moving in space with velocities 

 approaching to anything like 400 or 600 miles per 

 second. A little consideration will, however, show that 

 this is an objection which can hardly be admitted, as 

 we are not in a position to be able to perceive bodies 

 moving with such velocities. No body moving at the 

 rate of 400 miles per second could remain as a member 



* "Phil. Mag.," May, 1868. ' Climate and Time,' chap. 21. 



