68 THE CHEMISTRY OF THE SUN. [CHAP. v. 



that he could not agree with that investigator in assigning 

 to aqueous vapour the whole of five groups of lines extending 

 from D to A, and including the groups A and B. These groups, 

 Angstrom expressed his belief were truly telluric lines, but he 

 denied that they are due to aqueous vapour, relying upon the 

 fact that during very cold weather (once as low as 27 C.) in 

 January, 1864, the telluric lines near D, c, and a, as well as 

 those from a to B, had almost entirely disappeared : while the 

 groups A and B, and a third about midway between B and c, were 

 very intense. He therefore assigned these three groups to some 

 compound gas, carbonic acid for instance, from their resem- 

 blance to the spectra of compound gases, and more especially of 

 metallic oxides. 



Fig. 27 is a copy of Janssen's map of the telluric lines 

 between D and c. 



These lines have since been made the subject of many beautiful 

 researches by Smyth and others, but now that we have seen that 

 they belong truly to our atmosphere they possess no longer the 

 same interest for us in this inquiry, and we must dismiss them 

 from our consideration, because they deal with the earth's 

 chemistry and tell us nothing touching the chemistry of the sun. 



