by the contact of a Hydrogen-flame with various Bodies. 323 



ness then being seen with a brilliancy which seemed to vary 

 according to the length of time it had been exposed. Moreover, 

 if a piece of granite, brick, &c, which showed the blueness 

 vividly, was broken in two, the colour was invariably absent on 

 the newly-fractured surfaces. 



Upon trying a block of ice, I found the blue coloration was 

 produced here also, as soon as the hydrogen-flame touched its 

 surface ; but it was not so certain in its appearance as on other 

 bodies : it was best seen around the bottom of the block, or be- 

 tween two pieces of ice placed nearly in contact. Some liquids 

 as well as solids showed the blue colour when the hydrogen- 

 flame was brought down upon them. Occasionally it was to be 

 seen on the surface of water ; but invariably it appeared with 

 great brilliancy on sulphuric acid. With regard to the latter, 

 a mere trace of the liquid could be detected by the sudden ap- 

 pearance of the blue : what, however, was most remarkable, and 

 seemed extremely suggestive, was that the blueness did not dis- 

 appear even after a prolonged exposure of the acid to the flame, 

 the colour remaining undimmed throughout. As soon as the 

 flame was brought to bear upon the surface of the acid, contact 

 with the liquid was immediately announced by a vivid blue 

 light, of a splendour only comparable to the blue line observed 

 by Professor Tyndall in the spectrum of highly heated lithium 

 vapour. The blueness here, as elsewhere, shone from the body 

 itself, and did not in any way tinge the flame with its colour. 

 It appeared like a sudden luminosity emitted from the surface 

 of the liquid wherever the actual flame came in contact with it. 



The next inquiry which suggests itself is, whether the blueness 

 was peculiar to the contact of a hydrogen-flame, or could it be 

 excited by other sources ? To answer this, I tried a luminous 

 jet of coal-gas, the non-luminous flame issuing from a Bunsen's 

 burner, and flames of alcohol, bisulphide of carbon, carbonic 

 oxide, defiant and marsh-gas — each flame being reduced to about 

 the size of the jet of hydrogen employed. No trace of the blue 

 luminosity was seen with any of these flames. Bodies which 

 showed the colour strongly with burning hydrogen, when trans- 

 ferred to any of the foregoing flames were perfectly inert. Was 

 the blueness, then, to be attributed to the high temperature of 

 the hydrogen-flame, to its richness in chemical rays, or to its 

 possession of some other property ? I endeavoured to solve the 

 first part of this question by urging the different flames with the 

 blowpipe, and also by holding a piece of granite, which showed 

 the blueness vividly with hydrogen, in the still hotter oxyhy- 

 drogen-flaine ; but in no case was the blue colour produced. I 

 obtained, however, a very slight coloration by using oxygen and 

 coal-gas, allowing the latter to be rather in excess. Finally, on 



