TKADaACTlONS OK SECTION C. — PKESIDENTIAL ADDKESS. 07 V 



Section C— GEOLOdY. 

 Prksident op the Sectiox. — Professor Jons Joly, Sc.D., F.R.S. 



THURSDAY, SEPTUM JiFIi 3. 

 Tlie President delivered the following jiddress : — • 



UEANIUM AND GEOLOGY. 



iNTROnTJCTION. 



Ix our day but little time elapses between tlie discovery and its application. 

 Our starting-point is as recent as the year 1993, when Paul Curie and Laborde 

 showed experimentally that radium steadily maintains its temperature above its 

 surroundings. As in the case of many other momentous discoveries, prediction 

 and even calculation had pieceded it. Rutherford and McClung, two years before 

 the date of the experiment, had calculated the heat equivalent of the ionisation 

 effected by iiranium, radium, and thorium. Kven at this date (1903) there was 

 much to go upon, and ideas as to the cosmic influence of radio-activity were not 

 slow in spreading.^ 



I am sure that but few among those whom I am addressing have seen a 

 thermometer rising under the influence of a few centigrams of a radiam salt ; 

 but for those who pay due respect to the principles of thermodynamics, the mere 

 fact that at any moment the gold leaves of the electroscope may be set iu motion 

 by a trace of radium, or, better still, the perpetual motion of Strutt's 'radium 

 clock,' is all that is required as demonstration of the ceaseless outflow of energy 

 attending the events proceeding within the atomic systems. 



Although the term 'ceaseless' is justified in comparison with our own span of 

 existence, the radium clock will in point of fact run down, and the heat outflow 

 gradually diminish. Next year there will be les5 energy forthcoming to drive the 

 clock, and less heat given oft" by the radium by about the one three-thousandth 

 part of what now are evolved. As geologists accustomed to deal with millions 

 of years, we must conclude that these actions, so far from being ceaseless, are 

 ephemeral indeed, and that if importance is to be ascribed to radium as a geolo- 

 gical agent, v/e must seek to find if the radium now perishing oif the earth is not 

 made good by some more enduringly active substance. 



That uranium is the primary source of supply cannot be regarded as a matter 

 of inference only. The recent discovery of ionium by Boltwood serves to link 

 uranium and radium, and explains why it was that those who sought for radium 

 as the immediate oftspring of uranium found the latter apparently unproductive, 

 the actual relation of uranium to radium being that of grandparent. But even 

 were we without this connected knowledge, the fact of the invariable occurrence 



' See letters appearing in A'aturc of July 9 and September 24, 1903, from the late 



r. W E. Wilson and Sir George Dafwin referring to radium as a solar constituent 



and one from the writer (October 1, 1903) on its influence as a terrestrial constituent. 



