542 . TRANSACTIONS OF SECTION A. 



strip as in the experiments on the electric deflection. The distribution of activity 

 over the strip was measured and the magnitude of the deflection produced by 

 the magnetic field thus determined. 



By measuring the radius of curvature of the radiation in a magnetic field of 

 known strength the value 



— =7-26xl0 5 

 e 



was obtained. 



In later experiments the RaB recoiling from a platinum wire coated with 

 RaA was allowed to pass, in a magnetic field, through a slit and then fall upon 

 a brass strip for three minutes. The magnetic field was then reversed and the 

 radiation allowed to continue for seven minutes, until the RaA on the wire had 

 decayed to an inappreciable quantity. The brass strip was then removed and 

 placed on a photographic plate and left for several hours. The RaC formed 

 in situ from the RaB on the strip produced an impression on the photographic 

 plate when developed. It was found that there were two well-marked maxima 

 of intensity, representing the distribution of RaB reaching the strip with the 

 direct and reversed magnetic fields. By measuring the distance between these 

 maxima, and from the known dimensions of the apparatus, the radius of curva- 

 ture of the rays in a magnetic field of known strength was determined, giving 

 the value 



Wlt ' = 6-52xl0' s 

 e 



This value is in fair agreement with that obtained by the first method and is 

 probably somewhat more accurate. 



The value of — for the a particle from RaA has been found by Rutherford 



to be 3'4xl0 5 . Now, since the momentum of the a particle and that of the 

 recoiling atom must be the same, it follows from these numbers that RaB 

 carries the atomic charge of electricity, since the o particle carries twice that 

 charge. 



Taken in conjunction with the results of the experiments on the electrostatic 

 deflection, the velocity of the radium B particles is found to be 3'23xl0 7 cm. 

 per second and its atomic weight 194. 



6. On the Resolution of the Spectral Lines of Mercury. 

 By Professor J. C. McLennan and N. Macallum. 



In this communication a series of slides were exhibited which illustrated 

 the resolving power of a high-grade echelon spectroscope recently made by the 

 Adam Hilger Co. for the Physical Laboratory at Toronto. With this instrument 

 the green line of mercury 5461 AU was shown to consist of a central doublet 

 accompanied by three satellites of greater and by three of smaller wave-length, 

 and the blue line 4389 AU to consist of a central strong line accompanied by 

 three satellites of greater wave-length and by two of shorter wave-length. The 

 results are in good agreement with the components of the same lines recently 

 obtained by Gale and others with a 7-in. Michelson plane grating. 



Slides were also shown which illustrated the magnetic resolution of the 

 satellite of shortest wave-length of the line 5461 AU. Under magnetic fields of 

 2,000 Gauss this line was resolved into a quartet, the inner doublet of which 

 corresponded to vibrations parallel to the magnetic field and the outer to vibra- 

 tions perpendicular to the magnetic field. Measurements made on the displace- 

 ments of the lines constituting the quartet showed that the magnetic separation 

 of the two doublets corresponded approximately to three fourths and three halves 

 that of the outer components of a normal triplet. 



7. On the Active Deposit from Actinium. By W. T. Kennedy. 



This paper was presented by Professor McLennan, and contained an account 

 ot experiments made on the active deposit obtained when the emanation from 

 actinium was allowed to diffuse freely between two parallel plates placed about 



