882 Dr. Makower and Mr. Evans : Deflexion by Magnetic 



been worked out by Coffin *, and it was estimated that on 

 this account the effective length of the plates in our experi- 

 ments was about four per cent greater than their actual 

 length. In the calculation the value 9 '8 millimetres has 

 therefore been taken as the length of the plates instead of 

 their real length, 9*4 millimetres, and the numbers given in 

 column 3 of Table II. were thus obtained. 



An inspection of the calculated and experimental deflexions 

 shows them to be of the same order of magnitude, and we 

 may therefore conclude that if radium B carries the unit 

 charge of electricity, its atomic weight is of the order to be 

 expected on the disintegration theory of radioactivity. 



Our thanks are due to Professor Rutherford not only for 

 supplying us with the radium emanation necessary for the 

 experiments, but also for his interest in the work. 



XCVII. The Deflexion by a Magnetic Field of Radium B on 

 Becoil from Radium A. By W. Makower, M.A., JJ.Sc, 

 and E.'J. Evans. B.ScA 



[Plate XVI1L] 



IT has been shown by Russ and Makower % that radium B 

 is positively charged when it recoils from radium A and 

 that the " recoil-atoms" can be deflected by an electric field. 

 Some experiments have lately been made to measure the 

 deflexion suffered by the radium B when it passes through a 

 strong magnetic field. For this purpose a powerful electro- 

 magnet was constructed § capable of giving 10,000 lines per 

 square centimetre over an area 9 cm. by 5 cm., with the 

 poles 2 cm. apart. A glass tube of 2 cm. external diameter 



Fig. 1. 



»-•- 4 -i-.d. 



c .--f.UL 



IB 



containing the apparatus shown in fig. 1 was placed in this 

 gap between the poles ; the glass vessel could be rapidly 



* Coffin, Proceedings American Academy, xxxix. No. 19, 1903. 

 t Communicated by the Authors. 

 X Russ and Makower, Phil. Mag. supra, p. 875. 



§ We are indebted to Dr. R. Beattie for designing and supervising the 

 construction of this magnet. 



