16 president's address. 



Some Questions in Tehrestrial Physics. 



Ill the course of my address last year I dealt with some features 

 of oceanic physics and incidentally with a number of phenomena 

 having an important bearing on the study of certain great geolo- 

 gical problems. The facts and speculations which I then placed 

 before you were received with so much favour by members and 

 friends that I have decided on this occasion to discuss a few 

 interesting questions in terrestrial physics which have lately been 

 occupying a prominent position in scientific thought. 



Radium and the Earth's Internal Heat. — The very unex- 

 pected properties possessed by radium have elevated it to a 

 position of prominence quite out of proportion to the relative 

 extent of its occurrence in the earth's crust. Radium is probably 

 the rarest — as regards quantity obtainable — of any substance so 

 far isolated, and yet, so unique are its characteristics and so far- 

 reaching are the possibilities attaching to its presence, that, 

 though its very existence has onl}^ been known for a few years, 

 it is now the subject of more experimental stud}' than any other 

 body. Briefly, the reason why so much interest centres round 

 this substance is that it is considered to be in a state of disin- 

 tegration, a condition accompanied by a hitherto quite unsuspected 

 display of energy, manifesting itself in most i-emarkable ways. 

 The study of the properties of radium has disclosed the existence 

 of an enormous store of energy locked up in the constitution of 

 matter, and it is the phenomena accompanying the liberation of 

 this energy during the breaking up or disintegration of radium 

 that render the subject one of such great interest and importance. 

 The conclusion arrived at from careful observations on the rate 

 of decay of radium is that a given unit of this substance has a 

 life which may be stated as roughly about 2000 years. In other 

 words, an ounce or a pound or a ton of radium Avould, in the 

 course of some such period, no longer possess the peculiar properties 

 of the original substance, and would have lost materially in 

 weight. 



Radium is generally supposed to be itself a product of the slow 

 breaking up of uranium and certain other elements. Uranium 



