president's address. 11 



So powerful iw this electrical action of radiuui that a very seusitive 

 electrometer can detect the presence of a quantity of radium five hundred 

 thousand times more minute than that which can be detected by the 

 spectroscope (that is to say, by the spectroscopic examination of a flame in 

 which minute traces of radium ai-e present). (3) Radium actually realises 

 one of the properties of the hypothetical stone to which I compared it 

 giving out light and heat. For it does give out heat which it makes 

 itself incessantly and without appreciable loss of substance or energy 

 (' appreciable ' is here an important qualifying term). It is also faintly 

 self-luminous. Fairly sensitive thermometers show that a few granules of 

 radium salt have always a higher temperature than that of surrounding 

 bodies. Radium has been proved to give out enough heat to melt rather 

 more than its own weight of ice every hour ; enough heat in one hour to 

 raise its own weight of water from the freezing-point to the boiling-point. 

 After a year and six weeks a gram of radium has emitted enough heat to 

 raise the temperature of a thousand kilograms of water one degree. And 

 this is always going on. Even a small quantity of radium diffused through 

 the earth will suffice to keep up its temperature against all loss by 

 radiation ! If the sun consists of a fraction of one per cent, of radium, 

 this will account for and make good the heat that is annually lost by it. 



This is a tremendous fact, upsetting all the calculations of physicists 

 as to the duration in past and future of the sun's heat and the temperature 

 of the earth's surface. The geologists and the biologists have long con- 

 tended that some thousand million years must have passed during which 

 the earth's surface has presented approximately the same conditions of 

 temperature as at present, in order to allow time for the evolution of 

 living things and the formation of the aqueous deposits of the earth's 

 crust. The physicists, notably Professor Tait and Lord Kelvin, refused 

 to allow more than ten million years (which they subsequently increased 

 to a hundred million) — basing this estimate on the rate of cooling of a 

 sphere of the size and composition of the earth. They have assumed that 

 its material is self-cooling. But, as Huxley pointed out, mathematics 

 will not give a true i-esult when applied to erroneous data. It has now, 

 within these last five years, become evident that the earth's material is 

 not solf-cooling, but on the contrary self-heating. And away go the 

 restrictions imposed by physicists on geological time. Tiiey now are 

 willing to give us not merely a thousand million years, but as many more 

 as we want. 



And now I have to mention the strangest of all the proceedings of 

 radium — a proceeding in which the other radio-active bodies, actinium 

 and thorium, resemble it. This proceeding has been entirely Rutherford's 

 discovery in Canada, and his name must be always associated with it. 

 Radium (he discovered) is continually giving ofT, apart from and in 

 addition to the rectilinear darting rays of Becquerel— an ' emanation' — 

 a gaseous 'emanation.' This 'emanation' is radio-active — that is, 

 gives off Becquerel rays — an^l deposits ' something ' upon bodies brought 



