310 Bacon— Phenomena Observed in Crookes* Tubes. 



Art. XXVIIL— 6>/ the Phenomena Observed- in Crookes* 

 Tubes; by N. T. Bacon. 



No satisfactory explanation seems to have been made of the 

 phenomena characterizing prolonged discharges in a Crookes 

 tube. 



Results which have been recognized are A, discharge of 

 peculiar rays from the anode ; B, discharge of different pecu- 

 liar rays from the cathode ; C, gradual attenuation of the dis- 

 charges ; D, recrudescence of the discharges on heating the 

 walls of the tube ; and E, coating of the walls with platinum 

 black. 



The attempt has been made to explain C and D by suppos- 

 ing the vacuum to increase, beyond the point where the dis- 

 charges can pass, by absorption in the pores of the glass walls 

 of portions of the residual gases, and redischarge of these on 

 heating the tube. But this hardly seems rational. It is con- 

 trary to all our ideas that an intense vacuum should be intensi- 

 fied by absorption of gases in the walls of the containing vessel 

 in which the vacuum was originally produced. We should 

 expect instead a slow evolution of relics of the greater amount 

 of the same gases absorbed in the body of the glass under the 

 higher original pressure ; and furthermore, if any such effect 

 existed, it could hardly fail to result in a kind of osmotic trans- 

 fusion from the outside, where, as in this case, the containing 

 wall is often not over -jVoo i ncn thick. It seems reasonable 

 to ascribe the gradual attenuation to increasing vacuum, as it 

 is partly overcome by heating the walls of the tube. Glass is 

 known to have (and particularly with aqueous vapor) tl>e 

 property of accumulating over its surface a film denser than 

 the average of the surrounding atmosphere, and this is even 

 more marked with platinum. This I lay to lack, in the solid 

 state, of the perfect elasticity of the molecule, which is postu- 

 lated by the received theories of gaseous tension. Why should 

 we not consider molecular elasticity to be more or less imper- 

 fect in the solid state ? We should then find a ready explana- 

 tion of the heating of platinum sponge in an atmosphere of 

 hydrogen, accompanied by condensation of the hydrogen even 

 to the point of liquefaction. The molecule of hydrogen strik- 

 ing the imperfectly elastic platinum molecule would rebound 

 with diminished velocity, the lost kinetic energy going to raise 

 the temperature. In the pores of platinum sponge the hydro- 

 gen molecule will naturally strike again and again the imper- 

 fectly elastic mass, with further evolution of heat and loss of 

 velocity, until it reaches nearly the orbital velocity of the 

 vastly heavier platinum molecule, thus being reduced even to 



