36 



THE CHEMISTRY OF THE SUN. 



[CHAT-. 



blue, green, yellow, and orange were cut out and stopped, 



thus, 



V I B G Y O 



and by the defect of these rays the light became red. 



To record his observations Herschel adopted a device which 

 has since come into very general use. He represented the 

 prismatic spectrum by a horizontal line, indicating the various 

 colours by their initial letters, and then at all points where 

 light was transmitted he erected perpendiculars of lengths 



p n y G :B "V ^B y S B T 



FIG. 16. Copies of Herschel's Diagrams. 



proportionate to the intensity of the light observed ; connecting 

 the extremities of all these lines he obtained a curve which 

 he called the type of that particular medium. 



The accompanying figures which are copies of some of those 

 given by Herschel, show the sort of curves obtained. 



No. 1 represents the effect of ruby-red glass or port wine on 

 the spectrum. Nearly all the light transmitted is in the red. 

 No. 2 shows the effect of a particular green glass with a tend- 

 ency to redness. 3 shows the action of a solution of ammonio- 

 carbonate of copper in various thicknesses, the absorption 



