and on the chemical action of the Solar Spectrum. 273 



coloured glass and great thicknesses of 3'ellow fluid are deep- 

 ened to a plum-brown in less than an hour *. 



Under three inches of the bichromate of potassa the paper,. 

 f, became in eight hours sunshine of a full blue-brown. 



18. The flict of cress and pea plants growing green, under 

 the influence of such powerful light as penetrated Professor 

 Draper's yellow media, will not appear at all surprising when 

 we examine the rays which pass through such fluids. 



This I have done by forming a spectrum, interposing the 

 coloured body between the prism and the sun. The follow- 

 ing are the effects of a February sun at Devonport. 



Through a deep blue solution of the ammonia-sulphate of 

 copper, the violet, indigo,-4)lue, and a portion of the green rays 

 pass. 



Through solutions of the muriate, acetate and nitro-muriate 

 of copper with iron, the green ray, and a considerable portion 

 of the yellow; a trace of the blue also is evident. 



Tlirough solutions of the bichromate and chromate of po- 

 tassa, the chloride of gold and decoction of turmeric, the red, 

 the yellow and the green rays are seen, and by taking their 

 impression on a daguerreotype 'plate a line of the hlue is dis- 

 tinctly marked. 



Through nitro-muriate of cobalt in ammonia, carmine in 

 ammonia, and sulphuric acid and decoction of cochineal, the 

 red and yellow rays alone appear to penetrate. 



THE SPECTRUM. 



Dispersed light 



White 



Kose hue 

 White with shade 



of green 



Black band 



Dispersed light., 



-^'^ wimw^' 



* The papers which accompany this article were exposed under the 

 glasses and three-fourths of an inch of fluids for forty minutes. The order 

 of interference and consequent colouring is plainly shown. 



Phil Mag, S. 3. Vol, 16. No. 103. April 184<0. T 



