930 Prof. C, T. Knipp on Rays of Positive 



Plates 18, 20, 24 a, and 26 A are typical photographs, ami 

 are enlarged and reproduced in figs. 2, 3, 4, and 5 (PI. XVII.). 

 For plate 20 (fig. 3) we have 



P.D. between plates... =156 volts, 



Ac-field =1093 „ 



Hence, d = 1*52 „ 



1 >2 — ° 5? 



The data for this plate corresponding to an electrostatic 

 deflexion ,r — 4*5 mm. are given in the following table : — 



v from curve X 10". 



v calc. X 10 7 . 



sxio*. 



Elect, atomic weight. 



Element. 



312 



4"55 



•95 



105 



H+ 



215 



3-10 



•45 



22 



H 2 4- 



1-30 



1-9 



•166 



6 



C+ + 



•77 



11 



•057 



17-5 



+ 



In the above it should be remarked that there was some 

 uncertainty in setting the measuring instrument on x. This 

 set of curves belongs to type 1. The heads of the para- 

 bolas are shown but feebly in the photograph and not at all 

 in the reproduction. It is interesting to note that the 

 velocities given in the second column, calculated by means 

 of the energy equation 



are in each case greater (by about 40 per cent, for this 

 plate) than the corresponding values given by measurements 

 made on the curves. This is as it should be, for we expect 

 the carriers to be slowed down considerably by impact with 

 the molecules of the remaining gas in the tube. The fourth 

 column contains the electric atomic weights *. They show 

 that, the curves are most likely due to the hydrogen atom, 

 the hydrogen molecule, the atom of carbon with two charges, 

 and the atom of oxygen with one charge. 



The results calculated from the measurements made on 



* J. J. Thomson, Phil, Mag. vol. xxi. p. 234, Feb. 1911. 



