368 



KECENT PROGRESS IN PHYSICS. 



Similar results were obtained when other gases were in the receiver 

 under the atmospheric pressure. There were two limits for the in- 

 terval at w, between which the spark passed at one time at u, at 

 another at v; the interval at u being less than the least of these lim- 

 iting numbers, the spark passed always at u, but being greater than 

 the greatest of these numbers it always took place at v. The follow- 

 ing table indicates the limits at u for different gases, v having the 

 constant value of 0.62 inch : 



Air, s and S 



Oxj'gen, s and S 



Nitrogen, s and S. 



Hydrogen, s and S 



Carbonic acid, s and S... 



Olefiant gas, s and S 



Coal gas; s and S 



Muriatic acid gas, s and S 



Smallest. 



0.60 

 0.59 

 0.41 

 0.50 

 0. 55 

 0.59 

 0.30 

 0. 25 

 0. 56 

 0.5B 

 0.64 

 0.69 

 0. 37 

 0.47 

 0.89 

 0.67 



Greatest. 



0.79 

 0.68 

 0.60 

 0.52 

 0.69 

 0.70 

 0.44 

 0.30 

 0.72 

 0.60 

 0.86 

 0.77 

 0.61 

 0.58 

 1.32 

 0.75 



Mean. 



0.695 

 0. 635 

 0. 505 

 0.510 

 0.615 

 0.645 

 0. 370 

 0. 275 

 0. 640 

 0. 590 

 0.750 

 0. 730 

 0, 490 

 0. 525 

 1.105 

 0. 720 



A similar series of experiments gave for- 



Smallest. 



Greatest. 



Mean. 



Hydrogen i I 



Carbonic acid.. >sandS-|-- 



Olefiant gas ) ( 



0.23 

 0.51 

 0.66 



0.57 

 1.05 

 1.27 



0.400 

 0. 780 

 0. 965 



which does not coincide very well with the former results, a proof that 

 these numbers do not afford sufficient grounds for forming a conclu-i, 



sion. 



That within certain limits of distance at u the spark takes place 

 alternately at u or v, and consequently that there is not a single per- 

 manent value of 10 for each gas, over which the spark always happens 

 at V, but under always at u, depends upon accidents (such as particles 

 of dust floating in the air) of which we can give no account. 



If at one of the intervals a spark once passed there was generally a 

 strong tendency in it to appear at the same interval again. 



It is a remarkable circumstance that the range of distance u should 

 be much less when s and S are negative than when these balls are 



