238 Scientific Intelligence. 



defined to be " quantity of substance measured by the equal-arm 

 balance." With regard to the vortex-atom theory, Lord Kelvin 

 writes to the author " I am afraid it is not possible to explain all 

 the properties of matter by the vortex-atom theory alone." " I 

 have not found it helpful in respect to crystalline configurations, 

 or electrical, chemical or gravitational forces." The book con- 

 tains a thoughtful presentation of fundamental physical concepts 

 and cannot fail to be of much service to those students who 

 desire a philosophic knowledge of modern theories. g. f. b. 



8. Uranium Radiation, and the Electrical Conduction pro- 

 duced by it. — A very exhaustive investigation of this subject has 

 been published by Prof. Rutherford of McGill University. 

 Becquerel had stated that the uranium rays differed from the 

 Rontgen rays in this respect, that they can be refracted and polar- 

 ized. Professor Rutherford cannot find any evidence of refrac- 

 tion or polarization. The theory of ionization adopted by the 

 author supposes that the rays in passing through a gas produce 

 positively and negatively charged particles and that the number 

 produced per second depends on the intensity of the radiation 

 and the pressure. The term ion does not assume that the ion is 

 necessarily of atomic dimensions. These ions are supposed to be 

 carriers of electricity. Prof. Rutherford examines the theory that 

 energy is absorbed in producing the ions and that the absorption 

 is proportional to the number of ions produced and thus depends 

 on the pressure. If this theory is correct he points out that we 

 should obtain the following results : 



(1) Charged carriers produced through the volumes of the gas. 



(2) Ionization proportional to the intensity of the radiation and 

 the pressure. 



(3) Absorption of radiation proportional to pressure. 



(4) Existence of saturation current. 



(5) Rate of recombination of the ions proportional to the square 

 of the number present. 



(6) Partial separation of positive and negative ions. 



(7) Disturbance of potential gradient under certain conditions 

 between two plates exposed to the radiation. 



The experiments performed by the author indicate that the 

 theory affords a satisfactory explanation of the electrical con- 

 ductivity produced by uranium radiation. He shows also that 

 the uranium radiation is complex, and that there are present at 

 least two types, which he terms a- and /3-radiations. The char- 

 acter of the /3-radiation seems to be independent of the nature of 

 the filter through which it has passed, and passes through all 

 substances tried with far greater facility than the a radiations. 

 The photographic effects are due principally to the /3-rad/ations, 

 except when the uranium compounds are placed close to the pho- 

 tographic plate. The experiments on transparency of metallic 

 plates are not in accordance with those of Becquerel. The 

 absorption of the /3-radiation in gases is probably of the same 

 order as that of the X-rays. — Phil Mag., January, 1899, pp. 

 109-163. j. T . 



