produced in the Prismatic Spectrum^d 89 



Sesquichloride of iron, — (Fe^ CI3) ; reddish-brownv ' ' ■ ! 

 Perjltioride qfmangane&e (Mn2 FI7). — Greenish-yellow. This 

 .■is remarkable, as the perchloride gives a very distinct series. 

 Permanganic acid (MngOy). — Purple. This is beautifully 

 shown by allowing a drop of water to fall into a tube full of 

 the perchloride of manganese, when all the lines immediately 

 (disappear. 



!>!>. Indigo. — Splendid crimson vapour (CjgHgNOg)*^'";'"'^'? 

 Alizarine from madder. — Orange vapour {Q>^\i^cf>{^. Bcith 

 these substances require careful management in the sublima- 

 tion, as they are readily charred, and a small portion is always 

 decomposed, whatever the amount of care employed. 



In making experiments on coloured flames, I generally 

 used an alcoholic solution of the compound on which I was 

 experimenting. A common cotton wick supported in a small 

 glass tube furnished the lamp whose flame I wished to exa- 

 mine. This little lamp was placed opposite the fissure, in a 

 tin box, the side of which next the slit was permanently open, 

 whilst the opposite side was furnished with a door opening 

 outwards and upwards, so that by a string it could be raised 

 to admit the light of day, and would afterwards close by its 

 own weight when allowed to fall back. Fraunhofer's lines 

 (Plate III. fig. 7) thus again served as points of comparison ; 

 the comparison, though not rigidly accurate, being still very 

 nearly so, and perfectly sufficient for my purpose. 



Fig. 8 in Plate III. exhibits the remarkable spectrum given 

 by a solution of chloride of copper. Several intervals of abso- 

 lute darkness here occur, interrupted by bright lines of great 

 intensity, particularly in the green and blue spaces. The 

 general hue of the diffused light is a bluish-green. 



Fig. 9 represents the spectrum from the green light of bo- 

 racic acid, in which, besides the bright streak at D, five well- 

 marked bright bands occur in the yellow and green, and a 

 narrow line in the indigo. 



Fig. 10 is the spectrum from nitrate of strontia, the red and 

 orange portions of which are particularly developed, and are 

 crossed by three very strong black lines; a bright line will be 

 remarked ii>(he blue and another in the indigo. «anv'. m^'/ 



Fig. 11 is that from an alcoholic solution o^ chloride of cal- 

 cium ; besides the lines in the orange, there is a very brilliant 

 yellow streak at D, and two bright bands in the yellow : in 

 addition to these is a bright streak in the indigo. 



Fig. 12 represents the spectrum of a flame coloured by 

 chloride of barium. It is in its features intermediate between 

 that of strontia and lime ; the most remarkable character is in 



