312 DISCUSSIONS IN COSMOLOGY. 



3rd. " If suns or stars have been formed by collision 

 of bodies moving in space, proper motion can be none 

 other than the unused and unconverted energy of the 

 original components. And as stellar bodies are likely 

 of all sizes, and moving with all manner of velocities, 

 it must often happen, from the unequal force of the 

 impinging masses, that a large proportion of the 

 original motion must remain unconverted into heat. 

 Consequently, some of the stars ought, according to 

 the theory, to possess great velocities — which is not 

 the case, as none of the stars have a motion of more 

 than 30 or 40 miles per second." 



I freely admit that, if it could be proved that none 

 of the stars have a proper motion of more than 30 or 40 

 miles per second, it would at least be a formidable 

 difficulty in the way of accepting the theory. For it 

 would indeed be strange that, amidst all the diversity of 

 dimensions of heavenly bodies, it should invariably 

 happen that the resultant movement of the combined 

 masses should be reduced to such comparatively insignifi- 

 cant figures. But something more definite must yet be 

 known in reference to the motion of the stars before 

 this objection can be urged. 



All that we are at present warranted to assume is 

 simply that, of the comparatively few stars whose rate 

 of motion has been properly measured, none have a 

 greater velocity than 30 or 40 miles per second, while 

 nothing whatever is known with certainty as to the 

 rate of motion of the greater number of the stars. 



There seems to be a somewhat prevailing misappre- 

 hension regarding the extent of our knowledge of stellar 

 motions. Before we can ascertain the rate of motion 

 of a star from its angular displacement of position in 

 a given time, we must know its absolute distance. 

 But it is only of the few stars which show a well- 



