MEMOIR III.] INVISIBLE LINES IN THE SUN'S SPECTRUM. 



ent regions in succession, exposing the 

 sensitive surface to each for a suitable 

 length of time. 



In Fig. 10 I have given on the left 

 side a representation of the larger lines 

 of Fraunhofer ; the right side gives them 

 as obtained on a daguerreotype plate 

 which has been iodized to a yellow, 

 brought by the vapor of bromine to a 

 red, and then slightly exposed to the 

 vapor of chloride of iodine. The pho- 

 tograph is so adjusted as to have its H 

 lines by the side of those of Fraunhofer ,- 

 which have the same name. It will be 

 seen that there are beyond the red ray 

 three extra spectral lines, which I have 

 marked a, |3, 7. These, however, I have 

 only occasionally found, for from the 

 general diminution of effect in that re- 

 gion they do not always come out in a 

 plain and striking manner. None of 

 Fraunhofer's lines in the yellow and 

 green are given, but G and its compan- 

 ions are very strongly impressed, as also 

 the group about i. But by far the most 

 striking in the whole photograph are 

 those marked H and Ic. Then passing 

 beyond the violet and out of the visible 

 limits of the spectrum, four very strik- 

 ing groups make their appearance. To the first line of 

 each of these, in continuation of Fraunhofer's nomencla- 

 ture, I gave the designations M, N, O, P. In I there are 

 three lines, in M eight, in N three, in O four, and in P 

 five. 



Besides these larger groups, the photographs were 



Fig. 10. 



