SOME UNSOLVED SCIENTIFIC PROBLEMS 



the great age of the earth, of the immateriality of heat, 

 of the undulatory character of light, of chemical atom- 

 icy, of organic evolution. Contrariwise, the opposite 

 ideas to all of these had seemingly a safe supremacy 

 until the new facts drove them from the field. Who 

 shall say, then, what forlorn hope of to-day's science 

 may not be the conquering host of to-morrow? All 

 that one dare attempt is to cite the pretensions of a few 

 hypotheses that are struggling over the still contested 

 ground. 



SOLAR AND TELLURIC PROBLEMS 



Our sun being only a minor atom of the stellar peb- 

 ble, solar problems in general are of course stellar prob- 

 lems also. But there are certain special questions re- 

 garding which we are able to interrogate the sun because 

 of his proximity, and which have, furthermore, a pecul- 

 iar interest for the residents of our little globe because 

 of our dependence upon this particular star. One of the 

 most far-reaching of these is as to where the sun gets 

 the heat that he gives off in such liberal quantities. We 

 have already seen that Dr. Mayer, of conservation-of- 

 energy fame, was the first to ask this question. As soon 

 as the doctrine of the persistence and convertibility of 

 energy was grasped, about the middle of the century, it 

 became clear that this was one of the most puzzling of 

 questions. It did not at all suffice to answer that the 

 sun is a ball of fire, for computation showed that, at the 

 present rate of heat-giving, if the sun were a solid mass 

 of coal, he would be totally consumed in about five thou- 

 sand years. As no such decrease in size as this implies 



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