14:8 Chronicles of Science. [Jan., 



were made in a strong wrouglit-iron vessel furnished with a thick 

 glass plate of sufficient size to permit of the optical examination of 

 the flame. The aj^pearance of a jet of hydrogen burning in oxygen 

 under the ordinary atmospheric pressure is well known. On in- 

 creasing the pressure to two atmospheres, the previously feeble 

 luminosity is very markedly augmented, whilst at ten atmospheres' 

 pressure, the light emitted by a jet about one inch long is amply 

 sufficient to enable the observer to read a newspaper at a distance 

 of two feet from the flame, and this without any reflecting surface 

 behind the flame. Examined by the spectroscojje, the spectrum of 

 this flame is bright and perfectly continuous from red to violet. 



With a higher initial luminosity, the flame of carbonic oxide in 

 oxygen becomes much more luminous at a pressure of ten atmo- 

 spheres than a flame of hydrogen of the same size and burning 

 under the same pressure. The spectrum of carbonic oxide biurning. 

 in oxygen under a pressure of fourteen atmospheres is very brilliant 

 and perfectly continuous. 



If it be true that dense gases emit more light than rare ones 

 when ignited, the passage of the electric spark through diffi^rent 

 gases ought to produce an amount of light varying with the density 

 of the gas ; and Dr. Frankland has shown that electric sparks 

 passed, as nearly as possible under similar conditions, through 

 hydrogen, oxygen, chlorine, and sulphurous anhydride, emit light, 

 the intensity of which is very shght in the case of hydrogen, con- 

 siderable in that of oxygen, and very great in the case of chlorine 

 and sulphurous anhydride. On passing a stream of induction 

 sparks through the gas standing over liquefied sulphurous anhy- 

 dried in a strong tube at the ordinary temperature, when a pressure 

 of about three atmospheres was exerted by the gas, a very brilliant 

 light was obtained. A stream of induction sparks was passed 

 through air confined in a glass tube connected with a condensing 

 syringe, and the pressure of the air being then augmented to two 

 or three atmospheres, a very marked increase in the luminosity of 

 the sparks was observed, whilst on allowing the condensed air to 

 escape, the phenomena were reversed. 



Mr. Huggins, F.E.S., has submitted the light of Comet II., 1868, 

 to spectroscopic examination, and has found it, when examined with 

 a spectroscope furnished with two prisms of 60^, to be resolved into 

 three broad bright bands. 



The brightest band commences at about h, and extends nearly 

 to F. Another band begins at a distance beyond r, rather greater 

 than half the interval between h and f. The third band occurs 

 about midway between d and e. In the two more refrangible of 

 these bands, the light was brightest at the less refrangible end, and 

 gradually diminished towards the other limit of the bands. The 

 least refrangible of the three bands did not exhibit a similar grada- 



