437 
vious to every practical chemist. Four were always filled, and 
tried in succession. The light in this was a rich lilac, with a 
bright central portion. Platino-cyanide looked dull white; 
but uran glass and quinine drawings scarcely showed any- 
thing. 
‘© 22. Iodine acted so rapidly on the mercury, and obscured 
the glass, that I could observe nothing. 
«23. Hydrochloric acid was so bad a conductor, that I had 
difficulty in preventing the discharge from passing outside the 
bell. The light was yellowish-gray; no strata, and less fluo- 
rescence than hydrogen. 
*¢24. Cyanogen was not like any other I had seen: the 
light is a deep lilac, no blue at the negative electrode, but 
only a deeper tint of the general hue. It ts very fluorescent, 
not perhaps quite so much as air, and the discharge is less lu- 
minous. After some time a change takes place, for the light 
becomes greenish, and the strata are more sharp; perhaps 
cyanide of mercury is formed. 
“©25. Vapour of naphtha gave nothing peculiar; the light 
was livid blue, and scarcely a trace of fluorescence. 
“26. Vapour of alcohol: the light was brilliant beryl- 
green, and orange at the disc when positive ; bare trace of fluo- 
rescence with the platino-cyanide. 
“27. Fluoride of silicium gave an indefinite colour be- 
tween lilac and green, reaching nearly to the mercury, where 
it was a strong brownish-yellow. The disc, though iron and 
positive, was covered with stars of green light, and there was 
only the faintest fluorescence with platino-cyanide. 
“28. Dentoxide of nitrogen differed in nothing from air, 
except that when the disc was negative the combustion was 
more vivid, and sparks of burning iron were thrown off. 
<©29. Ammonia gave a pale livid light, with scarce a trace 
of fluorescence, though the strata were highly developed. 
*¢30. Vapour of water is so bad a conductor, that the 
discharge would not pass till the density in the receiver was 
