Intelligence and Miscellaneous Articles, 77 



according to which a pretty considerable absorbing-power for radiant 

 heat is possessed by carbonic acid, the author has attempted, in the 

 above investigation, to extend those observations, and to apply them 

 to the atmospheric absorption of the solar radiation. This view is 

 at variance with the generally accepted assumption that the aqueous 

 vapour of our atmosphere is the true absorbent of the sun's radia- 

 tion — an assumption the groundlessness of which the author has 

 demonstrated in another place. 



First, the radiation of a gas-lamp provided with a glass cylinder 

 was investigated ; and it was found that carbonic acid in a length 

 of 



214 536 705 917 917 millims. 



transmitted 



94-8 93-8 91-4 90 89 per cent. 



of the incident radiation. 



Further experiments (which, for the sake of the pure air, were 

 made out of Vienna, at G-reifenstein) show that the solar radiation 

 also suffers a considerable weakening on passing through carbonic 

 acid gas. A layer of this gas of one metre thickness absorbs about 

 13 per cent, when the sun's altitude is 59° ; this number lessens in 

 the same proportion as the sun descends. This proves that the 

 absorption of the solar radiation by carbonic acid is a selective ab- 

 sorption, and that the thicker the atmospheric layer through which 

 the rays have already passed, the scarcer do the absorbable wave- 

 lengths become. The author calculates from his experiments the 

 proportion of carbonic acid contained in the atmosphere, and finds 

 it to be 3*27 parts by volume in 10,000, which number agrees so 

 well with the data given elsewhere, and based upon chemical ana- 

 lysis, that there is the best prospect of determining in this way the 

 carbonic-acid content of the atmosphere, together with its varia- 

 tions and changes, accurately and also at heights where direct mea- 

 surements are impossible.— Kaiserliche Ahademie der Wissenschaften 

 in Wien, Sitz. d. math.-naturw. Classe, Nov. 4, 1880. 



SPECTRAL REACTION OF CHLORINE AND BROMINE. 

 BY M. LECOQ DE BOISBAUDRAN. 



When, by the old process, the spectrum of a small bead of chlo- 

 ride of barium is observed in a gas-flame, the lines proper to that 

 compound soon disappear and give place to those of the oxide. Yet 

 for a long time some chlorine remains in the baryta thus heated ; 

 the destruction of the BaCl 2 is only completed after its volatiliza- 

 tion. So, on drawing the induction-spark upon the small calcined 

 mass, the nebulous lines proper to BaCl 2 are very distinctly seen, 

 as well as the narrow barium-lines. 



