Discharges in Insulator 



443 



Pressure in millims 



of mercury 



M. P '639 



}xa 



544499445385266198 



602io77'547 503 439,402 

 I 



138 



361 301 



29 10-9 7-1 



258198 189 



i I 



It follows from these experiments that with pressures above 

 200 millims. the increase of the pressure is at least nearly pro- 



60f 









































si 















500 



















































































400 























































30< 





















































































100 











































#w& - $Z **" "-'- ' * ' "' 



H 



O 





















portional to the increase of the M. P. ; below that limit the 

 M. P. diminishes much more quickly in proportion. Similar 

 ratios were found with other gases. 



2. How, in a gas which is subjected to a fixed pressure, is 

 the quantity of electricity discharged connected with the dif- 

 ference of potential between the point and the plate ? 



Dry air, free from carbonic acid, was tried with the pres- 

 sures 391, 294, 203-4, 109-7, and 51'8 millims. mercury. The 

 highest difference of potential which could be determined with 

 my electrometer was 3684 units (6 units = 5 Daniells) ; the 

 greatest quantity of electricity that could be measured amounted 

 to something over 500 arbitrarily chosen units. The follow- 

 ing Tables contain in the first column the differences of poten- 

 tial, in the second the corresponding amounts of electricity 

 discharged ; and in the third I have given, under the name of 

 " disposable potential-differences," the differences between the 

 numbers in the first column and the M. P. corresponding to 

 each pressure, the quantity of electricity discharged being of 

 course =0. I have calculated these differences, and given 

 them the name above mentioned, because possibly the view is 



