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experiments on the air of the Irish Sea were, by the kind 
permission of the Honorable Board of Trinity House, made 
during the month of August 1865, on board the “ Bahama 
Bank” light vessel, situated in Lai. 54° 21' N, and Long. 4° 
11' W, seven miles W.N.W. of Ramsey, Isle of Man, and 
consequently nearly equidistant from the shores of England, 
Scotland, and Ireland. The times of observation were 4 a.m. 
and 4 p.m., the hours of nearly minimum and maximum 
temperature, when it was assumed that any differences in 
the air of day and night similar to those observed by Lewy 
over the Atlantic Ocean would be most perceptible. It 
appears from the 26 experiments embodied in the Table of 
Results accompanying the paper, that the mean quantity 
of carbonic acid in the air over the Irish Sea was in the 
month of August 1865, 3‘08 in 10,000 volumes of air — a 
very marked difference from the mean amount on the land, 
viz., 40 vols. in 10,000, as deduced from the most extensive 
observations on land-air. It was therefore concluded that 
the Sea in our latitudes does not act in increasing the amount 
of carbonic acid in the air above the ocean, as found by Lewy 
over the Atlantic near the equator. And it also appeared 
from those experiments that the differences observed in the 
air of night and day by Lewy over the Atlantic are not 
perceptible in the air above the Irish Sea. 
The kindness of Messrs. Alfred Booth and Co., of Liver- 
pool, has enabled the author to test the validity of Lewy’s 
conclusions respecting the composition of the atmosphere 
above the tropical oceans by a series of determinations of 
the amount of carbonic acid contained in the air of the 
Atlantic, made by Pettenkofer’s method, during a voyage 
to and from the Brazils. The bottles employed in collecting 
the air were however of increased capacity, since by thus 
experimenting on a larger volume of air any variations in the 
amount of atmospheric carbonic acid would, of course, be 
rendered more appreciable. From 51 experiments made 
