LIMITS OP INSULATION AND DISCHARGE IN GASES. 101 



the receiver a, the interval u was not a fixed one ; it might be altered through a cer- 

 tain range of distance, and yet sparks pass either there or at v in the receiver. The 

 extremes were therefore noted, i. e. the greatest distance short of that at which the 

 discharge always took place at v in the gas, and the least distance short of that at 

 which it always took place at u in the air. Thus, with air in the receiver, the extremes 

 at u were 0*56 and 079 of an inch, the range of 0-23 being one at which sparks passed 

 occasionally either at one interval or the other. 



1387. The small balls s and S could be rendered either positive or negative from 

 the machine, and as gases were expected and were found to differ from each other in 

 relation to this change, the results obtained under these differences of charge were 

 also noted. 



1388. The following is a Table of results; the gas named is that in the vessel a. 

 The smallest, greatest, and mean interval at u in air is expressed in parts of an inch, 

 the interval v being constantly 0*62 of an inch. 



Smallest. Greatest. Mean. 



rAir, Aand S, pos . 0-60 079 0*695 



1 Air, s and S, neg 0*59 0-68 0*635 



r Oxygen, 5 and S, pos 0*41 0*60 0*505 



1 Oxygen, 5 and S, neg 0*50 0*52 0*510 



f Nitrogen, ^ and S, pos 0*55 0*68 0*615 



1 Nitrogen, s and S, neg 0*59 070 0*645 



r Hydrogen, s and S, pos. . . . 0*30 0*44 0*370 



1 Hydrogen, s and S, neg. . . . 0*25 030 0*275 



r Carbonic acid, s and S, pos. . . 0*56 72 0*640 



1 Carbonic acid, s and S, neg. . . 0*58 0*60 0*590 



r Olefiant gas, s and S, pos. . . 064 0*86 0*750 



t Olefiant gas, s and S, neg. . . 0*69 0*77 0*730 



r Coal gas, * and S, pos 0*37 0*61 0*490 



1 Coal gas, s and S, neg 0*47 0*58 0*525 



Muriatic acid gas, s and S, pos. . 0*89 1*32 1*105 



Muriatic acid gas, s and S, neg. . 0*67 0*75 0*720 



1389. The above results were all obtained at one time. On other occasions other 

 experiments were made, which gave generally the same results as to order, though 

 not as to numbers. Thus: 



Hydrogen, s and S, pos 0*23 0*57 0*400 



Carbonic acid, 5 and S, pos. . . . 0*51 1*05 0*780 



Olefiant gas, 5 and S, pos. . . . 0*66 1*27 0965 



I did not notice the difference of the barometer on the days of experiment. 



1390. One would have expected only two distances^ one for each interval, for which 



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