SOME UNSOLVED SCIENTIFIC PROBLEMS 



ing geologist or biologist would content himself with a 

 fraction of that time. But the case for the geologist 

 was to receive yet another prop from the studies of 

 radio-activity, which seem to prove that the atom of 

 matter has in store a tremendous supply of potential 

 energy which may be drawn on in a way to vitiate 

 utterly all the computations to which I have just re- 

 ferred. Thus a particle of radium is giving out heat 

 incessantly in sufficient quantity to raise its own weight 

 of water to the boiling-point in an hour. The demon- 

 strated wide distribution of radio-active matter 

 making it at least an open question whether all matter 

 does not possess this property in some degree has led 

 to the suggestion that the total heat of the sun may 

 be due to radio-active matter in its substance. Ob- 

 viously, then, all estimates of the sun's age based on the 

 heat-supply must for the present be held quite in 

 abeyance. What is more to the point, however, is 

 the fact, which these varying estimates have made 

 patent, that computations of the age of the earth based 

 on any data at hand are little better than rough guesses. 

 Long before the definite estimates were undertaken,, 

 geologists had proved that the earth is very, very old, 

 and it can hardly be said that the attempted computa- 

 tions have added much of definiteness to that propo- 

 sition. They have, indeed, proved that the period of 

 time to be drawn upon is not infinite ; but the nebular 

 hypothesis, to say nothing of common-sense, carried us 

 as far as that long ago. 



If the computations in question have failed of their 

 direct purpose, however, they have been by no means 

 lacking in important collateral results. To mention 



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