— 15 — 
les: Celles du sodium et du carbone (la grande comete 
1882) Le spectre de la queue reproduisait l'aspect 
de celui du noyau, les raies etaient seulement beaucoup 
plus faibles, quoique bien visibles, taut Celles du sodium 
que du carbone». 
Copeland etLohse (Copernicus; 21, pgg. 236—243): 
«Judgiug frorn the totality of Ihe appearance presented 
by these four large comets (1881 et 1882), we are 
strongly inclined to think, that Ihe difference of spectra 
of nucleus, coma and tail is only one of intensity, ho 
wever that may be brought about»... 
c(On June 6 the whole Gomet Wells was seen brilli- 
antly in the light of sodium in an open slit, the tail as 
well as the head, and in the spectrum of the great co- 
met of 1882 all the hrighter lines extended through the 
whole length of the slit, being, however, fuller of light 
in the nucleus, thus indicating their presence in the nuc- 
leus as well as in the commencement of the taib)... 
«But not merely an odd one, nay, all the six hrighter 
lines observed in the green and yellow (la grande co- 
mete de 1882) correspond to the most prominent Iron 
lines in that part of the spectrum and even the two 
broad bands, noticed there, fall into a group of nume- 
rous Tron lines». — 
II me parail que par rapport aux observations spec- 
troscopiques on peut encore ajouter la remarque, que 
les bandes de l'hydrogene pur, plus faibles que Celles de 
ses combinaisons avec le carbone, doivent se placer sur 
les bandes obscures correspondantes du spectre continu 
(solaire) et par cela il sera toujours impossible de les 
discerner, sauf quelques circonstances exclusives. — 
5. M. Meyer, dans sa recherche interessante sur la re- 
fraction des rayons lumineux dans l'interieur d'une co- 
