CALORIFIC RELATIONS OF HYDROGEN AND OTHER GASES. 383 
“ Tt is thus evident that the combustion of an amount of gas which 
would give a light equal to 100 candles when the barometer stands 
at 81 inches, would give a light equal to only 84-4 candles if the 
barometer fell to 28 inches. 
* An inspection of all the above results shows that the erbetan 
of air, from atmospheric pressure downwards, produces a uniformly 
diminishing illuminating power until the pressure is reduced to 
about 14 inches of mercury, below which the diminution of light 
proceeds at a less rapid rate. The above determinations give 
approximately 5°1 per cent. as the mean reduction of light for each 
diminution of 1 inch of mercurial pressure down to 14 inches. I 
am now extending this inquiry to pressures exceeding that of the 
atmosphere, and hope soon to lay before the Society the detailed 
results of the whole series, together with some observations on the 
causes of this variation of luminosity.” 
ON THE CALORIFIC RELATIONS OF HYDROGEN AND 
OTHER GASES. 
ABSTRACT OF A PAPER BY PROFESSOR MAGNUS. 
(Translated from Poggendorff?s Annalen. No. 2, 1861.) 
“ Professor Magnus communicated to the Academy of Sciences of 
Berlin, on the 30th of July, 1860, a series of investigations respecting 
the conductibility, &c., of heat in various gases; and on the 7th of 
February, of this year, he laid before the Academy a second series 
of these investigations,* the principal results of which are given 
below : 
‘1. The final temperature indicated by a thermometer placed in a 
‘vessel warmed from above, varies according to the nature of the gas 
with which the vessel is filled. 
“2. In hydrogen this temperature becomes higher than in any 
other gas. 
* Ueber die Verbreitung der Warme in den Gasen. Pogg, Ann., Febuar, 1861. An ahe 
stract by the Editor of the Annalen, of an article published by Professor Magnus (in con- 
tinuation of some previous investigations on this subject) in the Monatsberichte der 
Akademie der Wissenchaften zu Berlin. Anabstract of this memoir, with some additional 
observations by M. Verdet, is also given in the Annales de Chimie et de Physique for March, 
1861 ; but in this, many of the conclusions, as given by Prof. Magnus, are omitted.—E. J. C. 
