November 4, 1898.] 



SCIENCE. 



607 



conductor; and they can be refracted and 

 probably reflected, at least diffusively. Un- 

 like uranium rays, they are not polarized by 

 transmission through tourmaline, therefore 

 resembling in this respect the Eontgen rays. 



Quite recently M. and Mdme. Curie have 

 announced a discovery which, if confirmed, 

 cannot fail to assist the investigation of this 

 obscure branch of physics. They have 

 brought to notice a new constituent of the 

 uranium mineral pitchblende, which in a 

 400-fold degree possesses uranium's mys- 

 terious power of emitting a form of energy 

 capable of impressing a photographic plate 

 and of discharging electricity by rendering 

 air a conductor. It also appears that the 

 radiant activity of the new bodj^, to which 

 the discoverers have given the name of 

 polonium, needs neither the excitation of 

 light nor the stimulus of electricity ; like 

 uranium, it draws its energy from some 

 constantly regenerating and hitherto un- 

 suspected store, exhaustless in amount. 



It has long been to me a haunting problem 

 how to reconcile this apparently boundless 

 outpour of energy with accepted canons. 

 But, as Dr. Johnstone Stoney reminds me, 

 the resources of molecular movements are 

 far from exhausted. There are many stores 

 of energy in nature that may be drawn on 

 by properly constituted bodies without very 

 obvious cause. Some time since I drew at- 

 tention to the enormous amount of locked- 

 up energy in the ether; nearer our experi- 

 mental grasp are the motions of the atoms 

 and molecules, and it is not difficult men- 

 tally so to modify Maxwell's demons as to 

 reduce them to the level of an inflexible law 

 and thus bring them within the ken of a 

 philosopher in search of a new tool. It is 

 possible to conceive a target capable of me- 

 chanically sifting from the molecules of the 

 surrounding air the quick from the slow 

 movers. This sifting of the swift moving 

 molecules is effected in liquids whenever 

 they evaporate, and in the case of the con- 



stituents of the atmosphere, wherever it 

 contains constituents light enough to drift 

 away molecule by molecule. In my mind's 

 eye I see such a target as a piece of metal 

 cooler than the surrounding air acquiring 

 the energy that gradually raises its temper- 

 ature from the outstanding effect of all its 

 encounters with the molecules of the air 

 about it ; I see another target of such a 

 structure that it throws off the slow moving 

 molecules with little exchange of energy, 

 but is so influenced by the quick moving 

 missiles that it appropriates to itself some 

 of their energy. Let uranium or polonium, 

 bodies of densest atoms, have a structure 

 that enables them to throw off the slow 

 moving molecules of the atmosphere, while 

 the quick moving molecules, smashing on to 

 the surface, have their energy reduced and 

 that of the target correspondingly increased. 

 The energy thus gained seems to be em- 

 ployed partly in dissociating some of the 

 molecules of the gas (or in inducing some 

 other condition which has the effect of ren- 

 dering the neighboring air in some degree 

 a conductor of electricitj^) and partly in 

 originating an undulation through the ether, 

 which, as it takes its rise in phenomena so 

 disconnected as the impacts of the mole- 

 cules of the air, must furnish a large con- 

 tingent of light waves of shortwave-length. 

 The shortness in the case of these Becquerel 

 rays appears to approach without attaining 

 the extreme shortness of ordinary Eontgeu 

 rays. The reduction of the speed of the 

 quick moving molecules would cool the 

 layer of air to which they belong, but this 

 cooling would rapidly be compensated by 

 radiation and conduction from thesurround- 

 ing atmosphere; under ordinary circum- 

 stances the difference of temperature would 

 scarcely be perceptible, and the uranium 

 would thus appear to perpetually emit rays 

 of energy with no apparent means of resto- 

 ration. 



The total energy of both thetranslational 



