FORM OF THE CONTINENTS— WATTS IQl 



Huxley, as our representative, took up the challenge in his address 

 to the Geological Society in 1869, and asked the pertinent question 

 "but is the earth nothing but a cooling mass 'like a hot water jar 

 such as is used in carriages' or 'a globe of sandstone'?" And he 

 was able to point out at least some agencies which might regenerate 

 the earth's heat or delay its loss. 



So it is only fitting that the great physicist, who imposed a narrow 

 limit to geological time, should have prepared the way for those who 

 have proved that the earth possesses in its radioactive substances 

 a "hidden reserve" capable of supplying a continuous recrudescence 

 of the energy wasted by radiation, thus lengthening out the time 

 required to complete its total loss. These later physicists have given 

 us time without stint; and, though this time is the merest fraction 

 of that envisaged by cosmogonists and astronomers, we are now so 

 much richer than our original estimates that we are embarrassed by 

 the wealth poured into our hands. So far from the last century's 

 urge to 'hurry up our phenomena", we are almost at a loss for 

 phenomena enough to fill up the time. 



The farsighted genius of Lord Rutherford and Lord Rayleigh 

 first saw the bearing of the rate of disintegration of radioactive sub- 

 stances in the minerals of rocks on the age of the parts of the earth 

 crust built of them. The extension and supplementing of this work 

 by Jol}^ Holmes, and others, has now enabled us to look to the dis- 

 integration of uranium, thorium, and potassium, as the most promis- 

 ing of many methods that have been used in the endeavor to ascertain 

 the age of those parts of the earth crust that are accessible to obser- 

 vation. These methods also promise a means of dating the geological 

 succession of eras and periods in terms of millions if not hundreds of 

 thousands of years. 



The decline and early death to which Lord Kelvin's dictum had 

 condemned the earth, according so little with the vigor displayed in 

 its geological story, is now transformed into a history of prolonged 

 though not perennial youth. It was for Joly, of whose work the 

 extent, variety, and fruitfulness are hardly yet fully appreciated, to 

 take the next step and see in the release of radioactive energy a 

 mechanism which could drive the pulse that geologists had so long 

 felt, and that Suess had so brilliantly diagnosed. As Darwin found 

 the missing word for Lyell, so Joly in his theory of thermal cycles 

 has indicated the direction of search for a mechanism to actuate the 

 rhythm of Suess. 



In Joly's conception the running down of the earth's energy, 

 though a continuous process, was, through the intervention of radio- 

 activity, converted into a series of cycles, during each of which rela- 

 tive movements of sea and land must occur; downward movements 

 of the continents, associated with positive encroachments of the sea ; 



