On Air subjected to X-rays. 535 



In addition to the above tabulated values the folio wing- 

 also have been obtained : — 



v = 285-64 



302-65 



293-26 



344-83 



366-32 



393-94 



R= 1790 



2-286 



2-182 



2-925 



3-473 



4-405 



v = 42600 



461-92 



531-33 



562-82 



582-35 



628-09 



R= 5-306 



6-784 



9-087 



10411 



11-586 



15-473 



v = 655-56 



669-53 



677-42 



691-32 



723-18 





R= 18-164 



19-998 



20419 



21-085 



23-896 





The curve is steeper than the nearest one of the family 

 R — ay 2 , and more nearly coincides with a curve of the family 

 R = ay 3 ; but more nearly still with a curve represented by 

 the equation TL = av 2 + bv 3 , as manifested by fig. 3, which is 

 the exact graph of the equation 



R = 0-000008r 2 + 0-000000049 v\ 



Thus the law of resistance so earnestly maintained by Col. 

 Duchemin, early in this century, and controverted by nearly 

 all later experimenters, seems to be corroborated by the 

 measurements made in this research, as far as they go. It 

 would be most interesting, therefore, to have records at higher 

 and lower velocities. 



I hope later to use a vertical gun of greater power, to 

 determine the resistance at all speeds from zero to 1400 feet 

 a second, in order to discover how Duchemin's equation 

 accords with the data of experiment throughout this range of 

 velocities. 



XLIX. How Air subjected to X-rays loses its Discharging Pro- 

 perty, and, hoiv it produces Electricity. By Prof. Jhnxio 

 Villari (Honorary Fellow of the Physical Society) *. 



THE apparatus used in my experiments is indicated by the 

 figure here adjoined (p. 536). 



A Crookes's tube C (fig. 1), enclosed in a small lead case 

 pp' with thick walls, was excited by a powerful inductorium 

 R, which, along with the small case pp' ', was enclosed in a 

 large case of zinc zz\ connected to earth by means of the 

 gas-pipes. 



The w r alls of the cases opposite to the anticathode had two 

 large openings through which there entered a vessel V quite 

 close to the Crookes's tube. This vessel, of cylindrical form 

 (30 centimetres by 11), was made of a thick sheet of lead, 

 with the exception of its base <x, turned towards C, which was 



* Communicated by the Physical Society : read Fob. 22nd, 1901. 



