90 On Lines prodticed in the Prismatic Spectrum. 



a bright streak in the orange, another in the yellow, and one 

 in the indigo. 



Even chloride of sodium, though the intensity of the light is 

 accumulated in the bright band near D, shows a marked ten- 

 dency to the occurrence of bands in other parts ; a distinct, 

 though faint light extending far into the indigo, when a bright 

 streak terminates it almost suddenly. 



Chloride of manga?tese gives indications of the occurrence 

 of bands, though but feebly. I have also tried solutions of 

 the chlorides of iron, zinc, cobalt, nickel, mercury and mag- 

 nesia: in all a feeble band occurs in the green portion, as re- 

 presented in the three last spectra; this is probably connected 

 with the disengagement of chlorine from the salts during com- 

 bustion ; and the bichloride of mercury gives a bright streak 

 near G in the indigo. 



The combustion of phosphorus in the open air gives a pure 

 spectrum without lines. 1 tried it also in chlorine, but did 

 not obtain any very clear spectrum, as the deposition of chlo- 

 ride on the jar quickly rendered it opake. 



Another source of light was furnished by the ignition of 

 different substances in the oxyhydrogen jet: the light thrown 

 directly upon the prism was too intense for the eye to bear, 

 I therefore received it on a sheet of white paper, and em- 

 ployed the diffused light so obtained. In the spectrum from 

 charcoal nearly midway between D and E, a very short bril- 

 liant streak was visible, and the same streak appeared when 

 the flame was thrown upon a fragment of dried alum. 



Lime and strontia gave results similar to those furnished by 

 the solution of their salts when used to tinge the flame of al- 

 cohol, but not quite so well marked. Baryta melted too 

 rapidly to furnish any satisfactory result. 



Zinc, iron, steel and platinum gave brilliant spectra, but no 

 lines except that at D were visible. Copper, lead and anti- 

 mony melted without giving light sufficient to make any satis- 

 factory observation. 



It may be interesting to remark, in connexion with the spe- 

 culations on the absorptive action of the sun's atmosphere, that 

 if solar light be transmitted through a flame exhibiting well- 

 marked black lines, these lines reappear in the compound 

 spectrum, provided the light of day be not too intense com- 

 pared with that of the coloured flame: this may be seen in the 

 red light of the nitrate of strontia, and less perfectly in the 

 green of the chloride of copper. It would therefore appear 

 that luminous atmospheres exist in which not only certain rays 

 are wanting, but which exercise a positive absorptive influence 

 upon other lights. 



