46 IN STARRY REALMS. 



conld be made to turn dynamos to generate electricity 

 enough for the wants of a mighty people. It is easy to 

 show that even in such a case also sunbeams would be un- 

 questionably the effective agents. Niagara is supplied by 

 the rain which falls over a vast tract of country ; that rain 

 is brought thither by the action of warm sunbeams, which 

 beat down on the oceans, evaporate the water, and raise it 

 aloft ; then the winds waft the vapour over the globe until 

 it again descends in the form of rain. Thus we learn that 

 the power of Niagara, no less than the efficiency of the 

 coal-fields in the production of heat and light, is to be 

 attributed to the sun, the difference being that in the one 

 case we are utilising the sun's ancient beams, and in the 

 other the power is provided from the radiation of the sun 

 at the present time. 



One more question may be briefly discussed. It will 

 be remembered that in what we have here said we are 

 merely discussing the natural consequences of those 

 laws of nature which are in operation around us. We 

 are tempted to push the inquiries back a stage earlier, 

 and examine how the materials of the sun came into the 

 nebulous state from which they have gradually become 

 transformed to the sun that we now have. It is quite 

 evident that the nebula cannot have existed from all time, 

 for were this so the sun must necessarily have long since 

 passed into that cold and inert condition which at present 

 is looked forward to in the dim future. It is, therefore, 

 interesting to inquire whether by the operation of natural 

 laws a vast glowing nebula could have been called into 

 being at some period not infinitely remote from the present 

 day. There is a possible, indeed a highly probable, ex- 



