S72 RECENT 'PROGEESS IN PHYSICS. 



evidently, that the small ball discharged in the negative state some- ' 

 what mure easily than in the positive, yet their result is not perfectly) 

 decisive, 



A contrivance, similar to that of fig. 73, was placed inside a glass i 

 vessel, which conld be filled with different gases. With equal inter- i 

 vals at n and o, Faraday obtained quite decided results for carbonic ;| 

 acid. When the conductor was positive the discharge took place i 

 mostly at o, when negative always at n ; here, then, the negative dis- r 

 charge was decidedly the more easy, and in coal gas the preponderance i 

 {•f the negative discharge was just as decided. In air and in oxygen r: 

 the greater facility of the negative discharge appeared -somewhat .1' 

 doubtful ; in nitrogen and in hydrogen there appeared some probability vj 

 of an opposite relation. 



Belli has made experiments, from which it follows that negative i 

 electricity escapes more easily into air than positive. — (Pog. Ann, 

 XXXV, 73.) 



After fastening a quadrant electrometer on a horizontal insulated 1 

 conductor and electrifying it 'positively, he found, as a mean of three :■' 

 experiments, that the electrometer required a period of ten minutes * 

 to sink from 20° to 10° ; but with negative electricity only 4.5 

 minutes were re(][uired. 



§ 81. Sparks in different gases. — The phenomena attendant on sparks 

 in different gases have been often observed and described. Faraday 

 has made experiments on this subject also, and describes them in the 

 twelfth series of his Experimental Kesearches. — (Pog. Ann. XLVII, 

 536.) 



The gases were under the pressure of the atmosphere ; the sparks 

 passed between brass balls. 



" In air," says Faraday, " the sparks have that intense light and 

 bluish color which are so well known, and often have iaint or dark 

 parts in their course, when the quantity of electricity passing is not 

 great, 



" In nitrogen they are very beautiful, having the same general ap- 

 pearance as in air, but have decidedly more color, of a bluish or purple 

 character, and, as I thought, were remarkably sonorous. 



"In oxygen the sparks were whiter than in air or nitrogen, and I 

 think not so brilliant. 



"In hydrogen they had a very fine crimson color" — "very little 

 sound was produced in this gas." 



" In carhcnic acid gas the color was similar to that of the spark in 

 air, but with a little green in it. The sparks were remarkably irregu- 

 lar in form, more so than in common air. 



" In muriatic acid gas the spark was nearly white. It was always 

 bright throughout, never presenting those dark spots which happen in 

 air, nitrogen^ and other gases. 



"In coal gas the spark was sometimes green, sometimes red, and 

 occasionally one part was green and another red ; black parts also 

 occurred very suddenly in the line of the spark." 



Sparks may be obtained in media, which are far denser than air — 

 as in oil of turpentine, olive oil, resin, glass, spermaceti, water, &c. 



