78 Intelligence and. Miscellaneous Articles. 



It is enough to pass the solar image in front of the aperture of the 

 collimator, so that at length the telescope only receives diffused light. 

 Most of Fraunhofer's lines appear then in a certain sense to become 

 effaced, while the others are strengthened ; these lines, which then 

 gain in intensity, are in general the intense lines of iron obtained 

 with the aid of the inductorium. 



Among the results arrived at in the research already cited, there 

 are two which appear worthy of attention. The first is, the certain 

 presence of manganese in the sun ; we have observed the coin- 

 cidence of at least thirty lines. The other is, the discovery of a 

 new hydrogen-line. The spectrum of hydrogen presents, as is 

 well known, three lines — two of which coincide with C and F, and 

 the third with a line near G. The fourth line which we have ob- 

 served is near the middle of the interval between G and H ; it coin- 

 cides with a very intense solar line which we have designated by 

 h. With Geissler's tube this line is very distinctly seen, although 

 it is much less feeble than the three others. This result is the more 

 satisfactory, as the line h was the only one among those of a cer- 

 tain intensity whose origin still appeared mysterious. The explana- 

 tion of it which we have found in the spectrum of hydrogen acquires 

 an additional interest from the fact that the line h occurs several times 

 in the stellar spectra drawn by Mr. Huggins. As the relative in- 

 tensity of the spectral lines of hydrogen greatly depends on the den- 

 sity and elastic force of the gas, we may probably draw some con- 

 clusions in this respect from the intensity of the corresponding 

 absorption-lines which exist in the solar spectrum. This is a sub- 

 ject to which I shall recur. — Comptes Rendus, Oct. 15, 1866. 



REMARKS ON THE ABOVE COMMUNICATION. BY M. JANSSEN. 



o 



The above observations of M. Angstrom refer to points of science 

 with which I have closely occupied myself, and I propose shortly to 

 discuss the results with the author. But among M. Angstrom's 

 results is one which, according to him, disaccords with the results 

 I have recently published on the spectrum of aqueous vapour. On 

 this point I shall reply at once. 



M. Angstrom, in measuring the wave-lengths of the solar spec- 

 trum, had occasion to observe telluric rays ; and having observed 

 that some of them continued even during very cold weather (when 

 the air, therefore, was extremely dry), he concludes that all the tel- 

 luric rays should not be attributed to the vapour of water. M. Ang- 

 strom especially cites A, B and a group between B and C. 



I will venture to remark that M. Angstrom is here combating 

 me with my own ideas. I have never thought or enounced that the 

 spectrum of aqueous vapour would represent the totality of the 

 telluric spectrum. My investigations on the terrestrial atmosphere 

 have had for their object to show that gases and vapours have at all 

 temperatures the power of elective absorption, and that spectrum 

 analysis might be applied to the study of the atmosphere of the 

 planets as well as to that of the sun. 



Thus, having observed that Sir David Brewster's bands were re- 



