472 



(he values of the different quantities, are as a niaximnni to each 

 olher in the ratio as recorded in table B. 



Continued experimental investigation on others than the examined 

 gases but also on the latter themselves can, however, still reveal 

 much. For all these investigations have been made within limits 

 for which it may be assumed that the natuie of the luminescent 

 centres and of the current-conducting ions does not undergo anj 

 essential change. We pointed out before that it follows from the 

 researches of J. Stark'), A. Wehnelt and J. Fkanck") tliat when 

 p is sufficiently reduced, and // sufficiently i-aised, the pressure-affect 

 reverses it sign '). It may, however, also be questioned, what happens, 

 when the natuie of the discharge is maintained, but the current- 

 density is greatly increased. We know only one indication of an 

 essential change taking place in this case ; already in I we expresse(M) 

 the desirability of examining by means of continued investigations 

 of the pressure-effect, whether anything could be derived from this 



[by making by estimation, an approximate calculation of the cathode and anode 

 gradient and the loss of potential between the electrodes end the entrances of 



TABLE C. 



p in m.m. Hg 



Terminal voltage 



Pot. diff. pos. column 



Thesis 



0.34 

 1.19 

 2.38 



212 Volt 

 288 „ 

 350 „ 



(ca. no Volt) 

 (ca. 240 „ ) 

 (ca. 290 „ ) 



table 4 



„ 10 



14 



the capillary path of the current]. Extrapolating we then find for p = 0.15: 

 pot. gradient in the pos. pile: about 145 Volts. If in connection with this we 

 assume llie pot. gradient to be '/s at 0.15 m.m. of that at Pi = 1.19 m.m. 



hence — = — 

 9^2 3 



, and if we bear in mind that we must a[)ply here the formula 



A p = f Ag j-^M, the following formula would follow from this 



J>, 



9t ' h 



5 6,5 



= 2,2. 



18 

 the ratio measured on nitrogen being — — = 2,3. 



^ 0,08 



More and more sharply defined measurements are very desirable also here. 



'j J. Stark. BoLTZMANN-Festschrift 1904. 



3) A. Wehnelt and J. Franck. Verh. d. D. phys. Ges. 12, 444 (1910), 



^) For convenience sake we shall distinguish this as "negative" effect from the 



"positive" effect found by us. 



*) Communication 1 loo. cit. 1178. 



