328 Effects of contact of a Hydro gen- flame with various Bodies* 



instant. But, from the brightness of the colour in the two 

 cases, it would appear that the homoeopathic doses of sulphur 

 are exceeded by the quantity we daily inhale with the atmo- 

 spheric dust. 



I must now briefly allude to another phenomenon which was 

 observed early in the foregoing investigation. In addition to the 

 blue colour seen on so many bodies, I found that contact of a 

 hydrogen-flame with some metallic surfaces gave rise to a second 

 appearance succeeding or sometimes accompanying the blue co- 

 loration. This was a bright scarlet spot encircled by a green 

 ring of light, forming together a section of the flame. The co- 

 loration now mentioned was not nearly so general in its appear- 

 ance as the sulphur-blue. On tin, or any of its alloys, it was 

 seen brightly, and it also momentarily appeared on any surface 

 which had been rubbed by these bodies. With a piece of thick 

 and tarnished tin-foil a beautiful experiment may be made. Scra- 

 ping the foil in places, and bringing it into contact with the hydro- 

 gen-flame, the blue colour is seen on the dull parts, and the scarlet 

 and green light appears on the bright surfaces, the latter remain- 

 ing until the foil melts. The colours may sometimes be made to 

 commingle, and a lovely purple is the result. On some clean 

 pieces of lead the same appearance was noticed ; but here it soon 

 faded away, and was probably only caused by the impurity of 

 the metal. On clean zinc it could not be seen; but after a piece 

 of tin plate had been drawn over its surface it appeared for an 

 instant. Like the blue coloration, this scarlet appearance could 

 not be obtained by exposing tin to a coal-gas or alcohol-flame, 

 nor to that of the oxyhydrogen blowpipe. An examination of 

 this colour through a spectroscope will, I trust, in a future in- 

 vestigation, throw more light on its nature. 



I may mention in passing, that I found many of the solids 

 examined phosphoresced brilliantly when held for a short time 

 in contact with the hydrogen-flame. This was the case with 

 marble, lime, selenite after it had been calcined by the flame or 

 with plaster of Paris, granite, sand-paper, and with different 

 kinds of writing-paper. On sand-paper, if the hydrogen be 

 suddenly extinguished, a phosphorescent image of the flame is 

 observed. Chalk gives a brilliant greenish light, which changes 

 into a still brighter yellow as lime is formed, the mass glowing 

 throughout on the continuance of the flame. 



The combustion of the hydrogen itself offers some points 

 worthy of further investigation. When burnt in an inverted 

 vessel, it is generally accompanied by the blue colour, which is 

 seen around the upper part of the flame where this is in contact 

 with the sides of the vessel. If, however, the hydrogen be 

 mixed with about a third its bulk of air, the blue colour becomes 



