SOME UNSOLVED SCIENTIFIC PROBLEMS 



dulatory character of light, of chemical atomicity, 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 hy- 

 potheses 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 

 problems also. But there are certain special ques- 

 tions regarding which we are able to interrogate the 

 sun because of his proximity, and which have, further- 

 more, a peculiar 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 per- 

 sistence 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 thousand 

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

 taken place within historic times, it was clear that some 

 other explanation must be sought. 



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