530 Sir DAVID BREWSTER on the Lines of the Solar Spectrum. 



are not distinctly defined. A very remarkable narrow one, cor- 

 responding to one produced by the nitrous acid gas, is situated 

 on the most refrangible side of C. Another very broad one lies 

 on the most refrangible side of D, close to a sharp and broad band 

 of yellow light, displayed by the general absorption of the corres- 

 ponding part of the superimposed blue spectrum. There is also 

 an imperfectly defined atmospheric action, corresponding to a 

 group of lines where Dr WOLLASTON placed his line C. 



This general description of the atmospheric lines, while it in- 

 dicates the remarkable fact, that the same absorptive elements 

 which exist in nitrous acid gas exist also in the atmospheres of 

 the sun and of the earth, leads us to anticipate very interesting 

 results from the examination of the spectra of the planets. FRAUN- 

 HOFER had observed in the spectra of Venus and Mars, some of 

 the principal lines of the solar spectrum. This, indeed, is a ne- 

 cessary consequence of their being illuminated by the sun, for 

 no change which the light of that luminary can undergo, is capa- 

 ble of replacing the rays which it has lost. But while we must 

 find in the spectra of the planets and their satellites, all the de- 

 fective lines in the solar spectrum, we may confidently look for 

 others arising from the double transit of the sun's light through 

 the atmospheres which surround them. 



ALLERLY, April 12. 1833. 



