150 SOME OF TEE LATEST ACHIEVEMENTS OF SCIENCE. 



Schmidt — omitted by thorium and its compoimds. The thorium rays 

 affect pliotographic plates through screens of paper or aluminum and 

 are absorbed by metals and other dense bodies. They ionize the air, 

 making it an electrical conductor, and they can be refracted and 

 probabl}^ reflected, at least diffusively. Unlike uranium rays, they 

 are not polarized by transmission through tourmaline, therefore 

 resembling in this respect the Rontgen rays. 



Quite recently Monsieur and ]\Iadamc Curie have announced a discov- 

 ery which, if confirmed, can not fail to assist the investigation of this 

 obscure branch of physics. They have brought to notice a new con- 

 stituentof the uranium mineral pitchblende, which in a four hundred-fold 

 degree possesses uranium's mysterious 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 body, to which the discoverers have given the 

 name of polonium, needs neither the excitation of light nor the stim- 

 idus of electricity; like uranium, it draws its energy from some 

 constantly regenerating and hitherto unsuspected store, exhaustless 

 in amount. 



It has long been to me a haunting problem how to reconcile this 

 apparentl}^ 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 attention to the enor- 

 mous amount of locked-up energy in the ether; nearer our experunental 

 grasp are the motions of the atoms and molecules, and it is not dith- 

 cult mentally so to modify Maxwell's demons as to reduce th(Mn 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 mechanically sifting from the molecules of the surround- 

 ing 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 constituents 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 tem- 

 perature 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 b}' 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 ena])les them to throw off the 

 slow-moving molecules of the atmosphere, while the quick-moving 



