12 ^ PKEStDENx's ADDRESS. 



near tliu radium no that they become railio-activc, and rciriuin so foi" 

 a time after the radium is itself removed. This emanation is always 

 being formed by a radium salt, and may be most easily collected by 

 dissolving the salt in water, when it comes away with a rush, as a gas. 

 Sixty milligrams of bromide of radium yielded to Ramsay and Soddy 0-124 

 (or about one-eighth) of a cubic millimetre of this gaseous emanation. 

 What is it ? It cannot be destroyed or altered by heat or by chemical 

 agents ; it is a heavy gas, having a molecular density of 100, and it can 

 be condensed to a liquid by exposing it to the great cold of liquid air. It 

 gives a peculiar spectrum of its own, and is probably a hitherto unknown 

 inert gas — a new element similar to argon. But this by no means 

 completes its history, even so far as experiments have as yet gone. The 

 radium emanation decays, changes its character altogether, and loses 

 half its radio-activity every four days. Precisely at the same rate as it 

 decays the specimen of radium salt from which it was removed forms a 

 new quantity of emanation, having just the amount of radio-activity 

 which has been lost by the old emanation. All is not known about the 

 decay of the emanation, but one thing is absolutely certain, having 

 first been discovered by Ramsay and Soddy and subsequently confirmed 

 by independent experiment by Madame Curie. It is this : After being kept 

 three or four days the emanation becomes, in part at least, converted into 

 helium — the light gas (second only in the list of elements to hydrogen), the 

 gas found twenty-five years ago by Lockyer in the sun, and since obtained 

 in some quantities from rare radio-active minerals by Ramsay ! The proof 

 of the formation of helium from the radium emanation is, of course, obtained 

 by the spectroscope, and its evidence is beyond assail. Here, then, is the 

 partial conversion or decay of one element, radium, through an inter- 

 mediate stage into another. And not only that, but if, as seems probable, 

 the presence of helium indicates the previous presence of radium, we have 

 the evidence of enormous quantities of radium in the sun, for we know 

 helium is there in vast quantity. Not only that, but inasmuch as helium 

 lias been discovered in most hot springs and in various radio-active minerals 

 in the earth, it may be legitimately ai-gued that no inconsiderable quantity 

 of radium is present in the earth. Indeed, it now seems probable that there 

 is enough radium in the sun to keep up its continual output of lieat, and 

 enough in the earth to make good its loss of lieat b}' radiation into space, for 

 an almost indefinite period. Other experiments of a similar kind have 

 rendered it practically certain that radium itself is formed by a somewhat 

 similar transformation of uranium, so that our ideas as to the permanence 

 and immutability on this globe of the chemical elements are destroyed, and 

 must give place to new conceptions. It seems not improbable that the 

 final product of the radium emanation after the helium is removed is or 

 becomes the metal lead ! 



It must be obvious from all the foregoing that radium is very slowly, 

 but none the less surely, destroying itself. There is a definite loss of 

 particles which, in the course of time, must lead to the destruction of the 



