38 Scientific Proceedings, Royal Dublin Society. 
brought home by two expeditions from the Parry Islands. Obser- 
vations made on these extend only to estimations of their oxygen by 
explosion. If, however, we may regard the carbonic acid in air as 
inversely proportionate to the oxygen*, the percentages of the latter 
ascertained to exist in these samples will afford data for comparison 
with the estimations of carbonic acid made during our expedition. 
Sir Edward Parry, in 1823, collected two specimens of early 
spring air at Igloolik. They were taken from inside his observa- 
tory, and were enclosed in glass bottles with brass stoppers. 
Faraday made two estimations from each sample by Doberiener’s 
eudiometrical process, and in every case found the percentage of 
oxygen less than in the air of the Royal Institution at the time 
of analysisf. The mean difference amounted to no less than 1°374, 
a difference due as much to the most unusually high amount in 
the air of the laboratory as to the low percentage in the Arctic 
air. The latter referred to the generally recognized average 20°98 
shows a deficit of °392. 
Sir James Ross brought home seventeen samples of air (not 
all Arctic) from Baffin’s Sea and Port Leopold—73-52 N. 90-12 W. 
They were taken at different seasons in 1848 and 1849, and sealed 
in glass tubes by fusion, They were examined by Regnault by 
explosion, and the results supply one of the tables in his researches 
on the composition of the atmosphere}. He remarks (as Frank- 
land does of the air of the Alps) that the percentage of oxygen in 
the Arctic air falls within the limits of observed variations, but 
an inspection of his table will show that not one of the samples 
possessed the normal 20:98 of oxygen ; the lowest shows a deficit 
of 13, and the mean of all 074. 
My estimations of carbonic acid in Polar air have been pub- 
lished in the report of the Parliamentary Committee on the out- 
break of scurvy during the Expedition, and Professor De Chaumont 
has done me the honour to quote them in his recent edition of 
Parke’s classical work on Hygiene. Itherefore bring them before 
you solely in their relation to the generalization which they tend 
to confirm. I add some particulars because results even in the © 
hands of the most practised investigators are—as has been pointed 
o 
f=) 
x Frankland’s Experimental Researches, p. 476—Angus Smith, Air and Rain, p. 59. 
+ Sir E. Parry’s 2nd yoyage—appendix p. 240. 
{ Annales de Chimie, 3rd series, vol. xxxvi., p. 404. 
