168 E. W. Morley— Oxygen in the Air. 
Art, XXVII.—On a possible cause of variation in the proportion 
of Oxygen in the Air; by Epw. W. Mortey, M.D 
., PH.D. 
Professor of Chemistry in Western Reserve College, Hudson, 
Ohio. 
Proressor Loomis has proposed the theory that certain 
great and sudden depressions of temperature at the surface o 
the earth are caused, not by the transfer of cold air from higher 
to lower latitudes, but by the vertical descent of air from cold 
elevated parts of the atmosphere. The evidence supporting 
this theory was published in this Journal in January and July, 
1875. It occurred to the writer some time since that if this 
theory were true, as the evidence makes very probable, the air 
at the surface of the earth during such a great and sudden 
depression of temperature might well contain a smaller propor- 
tion of oxygen than the average. Dalton, reasoning from the 
fact that oxygen has a greater specific gravity than nitrogen, 
argued that the proportion of oxygen to nitrogen in the atmo- 
sphere should decrease with increasing altitude above the 
earth’s surface; whether he clearly enough recognized that 
such a regular decrease would be realized only in an atmo- 
sphere in a state of equilibrium undisturbed by convection 
currents, the writer does not know, not having seen Dalton’s 
memoir. Such a decrease of atmospheric oxygen with increas- 
ing altitude has not yet been detected by analysis, although the 
amount of decrease, on the theory that oxygen and nitrogen 
are distributed in the atmosphere according to the law which 
would prevail in case of equilibrium, is so rapid that it would 
be detected with ease, even in altitudes attained in every holi- 
day ascent of a balloon. This decrease may be calculated from 
the formula R=R,0-9832960 ®, where H denotes the height 
above the earth’s surface expressed in kilometers, Ry denotes 
the ratio of the tension of oxygen to that of nitrogen at the 
surface of the earth, and R denotes the same ratio for the 
height H. The constant. is computed from the determinations 
by Regnault of the weights of a litre of oxygen and of nitro- 
gen, and of the specific gravity of mercury. The following 
table gives in the second column the ratio of the tension of 
oxygen to that of nitrogen at the height in kilometers given 1n 
_the first column, and the per cent of oxygen at the same 
height in the third column. The per centage of oxygen at the 
_ earth’s surface assumed in the table is that used in the tables 
for gas analysis in Bunsen’s Gasometrische Methoden. 
_ It will be seen that the composition here calculated for a 
height of a single kilometer isso different from that at the sur- 
face that analysis of no very refined accuracy would detect the 
