20 Prof. E. Edlund's Researches on the Passage 



must, according to what has been said above, be greater than 

 the latter. On the other hand, the observations show that the 

 deflection at a pressure of 5*4 millim., for example, is smaller 

 when the electrodes are at a greater distance from one another 

 than when they are closer. Ohm's law therefore, in its ori- 

 ginal form, is not applicable to the case in which the current 

 passes through a gaseous body. 



When, on the contrary, the current-intensities are propor- 

 tional to e—r-Jj and e x — GrJ, there is no contradiction in the 

 circumstance that at the low pressure ei—-6r l l>e—rilyfhile 

 at the same time, at the higher pressure, pei—n6r l l<pe—nr i l. 



Experiment 8. In this experiment on the passage of elec- 

 tricity through rarefied air, one of the electrodes consisted of 

 an aluminium wire, and the other of a platinum wire of ap- 

 proximately the same thickness. The discharge passed alter- 

 nately from the platinum to the aluminium, and from the latter 

 electrode to the former. In the circuit, at w, a rheostat with a 

 resistance of 21*5 ohmads was inserted. In this way the fol- 

 lowing results were obtained: — 



Pressure of 



■f.Vip niv 



Deflection when the discharge went 



A 



millim. 



from aluminium 



from platinum 





to platinum. 



to aluminium. 



22 . 



. . 11-65 



6-85 



3-4 . 



. . 14-35 



7-22 



3-8 . 



. . 15-05 



7-05 



6-5 . 



. . 11-90 



6-40 



24-1 . 



. . 5-10 



3-30 



35-7 . 



. . 3-55 



2-85 





If the electricity did not pass through the rarefied-air space, 

 a deflection of 1*9 scale-division was obtained when the dis- 

 charge from the electrophorus passed through the galvano- 

 meter circuit. 



The disjunction-current was therefore always less when the 

 discharge passed from platinum to aluminium than when it 

 pursued the contrary direction. Consequently aluminium as 

 the negative pole of the discharge gives a weaker disjunction- 

 current than a platinum negative pole. As, with such slight 

 pressures of air as the preceding, no particles of metal are 

 conveyed in the gaseous state from one pole to the other, the 

 air between the poles is not mixed with foreign particles 

 during the discharge ; and hence its resistance r x l is not de- 

 pendent on whether the discharge passes from aluminium to 

 platinum or whether it takes the contrary direction. The 

 cause of the difference between the amount of current in the 



