218 Mary Somerville. 



that by a recent vote of the Astronomical Society I can 

 now claim Mrs. Somerville as a colleague. Pray make 

 my compliments to her in that capacity, and tell her 

 that I hope to meet her there at some future session. . . . 

 Yours very faithfully, 



H. W. HERSCHEL. 

 To WILLIAM SOMEEVILLE, ESQ. 



Spectrum analysis has shown that there is 

 a vast quantity of self-luminous gaseous matter 

 in space, incapable of being reduced into stars, 

 however powerful the telescope through which 

 it is observed. Hence the old opinion once more 

 prevails, that this is the matter of which the sun 

 and stellar systems have been formed, and that 

 other stellar systems are being formed by slow, con- 

 tinuous condensation. The principal constituents 

 of this matter are, the terrestrial gases, hydrogen, 

 and nitrogen. The yellow stars, like the sun, con- 

 tain terrestrial matter. The nebulous and stellar 

 constituents were chiefly discovered by Dr. Huggins. 



Somerville and I were always made welcome by Sir 

 James South, and at Camden Hill I learnt the method 

 of observing, and sometimes made observations my- 

 self on the double stars and binary systems, which, 

 worthless as they were, enabled me to describe better 

 what others had done. One forenoon Somerville and 

 I went to pay a visit to Lady South. Sir James, who 



