130 G. F. BECKER RELATIONS OF RADIOACTIVITY TO COSMOGONY 



from tmiform, depending on the environment, and furnishes no safe 

 guide to the lapse of time. Such studies as those of Mr de Aeries on plants 

 and of Mr Weldon on crabs show that under some circumstances specific 

 modulation may be very rapid. Mr Walcott and Mr Sollas speak with 

 authority, both as biologists and stratigraphers, and each expresses the 

 conviction that his estimate from the strata is not inconsisent with the 

 life record. 



It would appear, then, that geology points to an age of the ocean which 

 probably lies somewhere between 50 and 75 million years. For such a 

 period there is also physical evidence wholly independent of the origin of 

 the heat of the solar system. Sir George Darwin's studies of the earth- 

 moon system led him to believe that the two planets parted company 

 something over 54 million years ago.*' 



The age of the earth, considered as a cooling body, was computed by 

 Clarence King,*" using Kelvin's formulas under restrictions established 

 by Mr Barus, at 24 million years, and this result was accepted by Kel- 

 vin *' in his last paper on this great subject. The uniform initial tem- 

 perature of this earth was 1,950° centigrade. 



No one, I fancy, will be inclined to deny that the earth really is a 

 cooling body of nebulous origin, and that a part of its heat is due to 

 compression. Kant *^ in 1785 was the first to refer the heat of stellar 

 bodies to the compression of nebulous matter, and Helmholtz *^ in 1854 

 was able to deal further with the subject, quantitatively in part, thanks 

 to Joule's determination of the mechanical equivalent of heat. Once this 

 cause of high temperatures was pointed out, its importance could not 

 and can not be denied. 



« Philosophical Transactions, vol. 170, 1879, p. 511, and vol. 171, 1880, p. 882. 



*° American Journal of Science, vol. 45, 1893, p. 1. 



*' Transactions of the Victoria Institute, vol. 31, 1899, p. 11. 



*^ "Die Vulcane im Monde," 1785. The earliest expression of great ideas is always 

 a matter of interest, and I therefore translate some passages of Kant's paper : "Whence 

 came the original heat? . . . Whence came the heat of the sun? If it is assumed 

 (as is probable, on other grounds) that the protyle of celestial bodies was originally 

 distributed in a vaporous state throughout the whole space in which they now move, 

 and that they have formed according to natural laws, as first by chemical affinity, 

 but afterwards and chiefly in obedience to universal attraction, then [Adair] Craw- 

 ford's discovery points the way to a comprehension of how any temperature you please . 

 might be produced simultaneously with the genesis of celestial bodies. ... If, as 

 he proves, matter expanded in vapor contains far more heat, and Indeed, to maintain 

 Its expansion, requires far more heat, than when condensed — in other words, when 

 nebulous matter is compressed to stellar bodies — then the resulting globes must con- 

 tan more caloric than would suffice to maintain the natural equilibrium with the caloric 

 of surrounding space." He goes on to explain that the amount of heat generated must 

 be a direct function of the mass of the stellar body, and adds : "In this way we should 

 comprehend why the central body, as that of greatest mass in any system, may be the 

 hottest, and so in every case a sun." 



" Die Wechselwlrkung der Wissenschaften, 1854. 



