63 
during the months of February, March, and July 1866, it 
appears that the mean quantity of carbonic acid contained 
in the air of the Atlantic Ocean is 2*953 vols. in 10,000 of 
air : in that of the Irish Sea it was, from 26 experiments, 
3*082 : the mean of the 77 experiments being 3*00. 
This result compared with the following numbers giving 
the amount of carbonic acid contained in land air, shows 
that, contrary to the statement of Lewy, the air over the 
ocean contains a much smaller proportion of carbonic acid 
than that of the land. 
The most extensive observations on land air have given 
as means : — 
Observer. 
Locality 
No. of Yols. in 
Expts. 10,000 in air; 
Th. de Saussure... 
Chambeisy 
... 104 ...... 
, 4*15 
Boussingault 
, Paris i . . . . 
... 142 
3-97 
Verver 
. Groningen 
... 90 
. 4*20 
Koscoe 
. London and Manchester. 161 
. 3*95 
Angus Smith 
Ditto ditto 
200 
. 4*03 
General mean of observations on land air 
. 4-04 
Independent 
Expts. 
General mean, observations on sea air, Lewy. . . 11 
. 4*63 
Ditto ditto ditto Thorpe 44 3*00 
The quantity of carbonic acid contained in land air is 
subject to continual alteration from the variable circum- 
stances of locality, temperature, fog, rain, &c. ; it may thus 
vary from 2*5 to 8 volumes in 10,000 of air. It would 
appear, however, from the above experiments that the 
amount of carbonic acid in sea air experiences fewer and 
far less extensive variations : it is sensibly the same in 
different latitudes and is constant in the same locality 
throughout the year. The mean quantity of carbonic acid 
contained in sea air between the parallels 15° and 30° N* 
latitude was in the months of February and March 1866, 
2*96 in 10,000 volumes of air; in July of the same year it 
