180 Scientific Proceedings, Royal Dublin Society. 
If we accept Thorpe’s figures for tropical Brazil as representing 
the amount of carbonic anhydride in the air of the tropics, and 
omit Mintz and Aubin’s figures for central and southern America, 
then the Table undoubtedly indicates a diminution for higher 
latitudes in the northern hemisphere, which, with afew exceptions, 
would appear to be progressive and to hoid good both for the mean 
and minimum amounts. 
Mintz and Aubin’s figures are somewhat puzzling, whether 
tuken alone, or in conjunction with those of the other observers. 
The mean amount found at Florida (2:90) is, it is true, higher than 
the mean for the Plain of Vincennes (2°83) or on the Pyrennean 
mountains (2°86); but at Mexico a sudden drop occurs, and at 
Martinique the figure (2°73) is actually lower than at the Plain of 
Vincennes. Again, in the southern hemisphere they found a larger 
proportion at Chubut (2°79) than at Chili (2°66), where a surprisingly 
low amount was obtained. But further south the results are cer- 
tainly in harmony with Schleesing’s theory : thus, at Santa Cruz a 
mean of 2°66 was found, and it is interesting to note that Dragen- 
dorff found precisely the same amount at Dorpat. Lastly, at Cape 
Horn 2°56 was found as a mean—the lowest mean figure we 
believe recorded by any of the observers. Here the interesting 
observation was made that the amount of atmospheric carbonic 
anhydride varied with the temperature of the sea water, 2-530 
being obtained as the mean volume for temperatures below 5° C. 
and 2°598 for temperatures above 5° C. 
Thorpe made determinations of carbonic anhydride in the air 
of the Atlantic almost daily (after Madeira was reached) during 
a voyage from Liverpool to South America. He was thus work- 
ing under very favourable conditions for tracing variations depen- 
dent on latitude. Unfortunately, he does not specifically state the 
latitudes corresponding with the different observations, but a 
study of the numbers obtained by him reveals no steady increase 
as the equator was reached. he variations were irregular, but 
the lowest figure of all (2°69) was obtained when he must have 
been near the equator. He himself says the amount “is sen- 
sibly the same in different latitudes.” Thus, there is evidence 
both for and against variations in the amount of atmospheric car- 
bonie anhydride depending on latitude, but the experimental data 
are altogether insufficient to enable a definite conclusion either, one 
