37 
Ramsey, Isle of Man, and consequently nearly equidistant 
from the nearest shores of England, Scotland, and Ireland. 
The ship is placed to mark the proximity of a dangerous bank, 
by which, for the greater part of the day, a strong current, 
setting in from the southward, flows through the North Chan- 
nel and thence into the Atlantic. 
These experiments were made in the early part of August, 
at the same periods of the twenty-four hours, namely about 
4 a.m. and 4 p.m , or nearly the times of minimum and 
maximum temperature. 
Pettenkofer’s method of analysis was adopted, with the 
improvements in the practical details suggested by Angus 
Smith. This method is in principle similar to the one 
adopted by Watson and Emmet, but admits of far more deli- 
cacy and precision in practice. Baryta is substituted for 
lime water, and oxalic for sulphuric acid. The solution of 
oxalic acid for these experiments was made so that one cubic 
centimetre of it corresponded to one milligramme of carbonic 
acid ; it thus contained £'864 grms. of pure crystallised oxalic 
acid per litre. Twenty-five cubic centimetres of the baryta 
solution were originally made to correspond to about twenty- 
eight of oxalic acid, but of course the exact strength of the 
baryta water was ascertained previous to each experiment. 
The bottles were generally filled with the air by means of the 
bellows, but sometimes when the wind was strong it sufficed 
to hold them up for a minute or two in such a manner that 
the air could circulate freely within. The baryta water 
remained in contact with the enclosed air for three quarters of 
an hour to one hour, during which time the bottles were fre- 
quently agitated. Although even this is longer perhaps than 
is actually required for the complete absorption of the car- 
bonic acid, still, for the sake of conclusiveness, in experiment 
4 the bottles were allowed to stand for three hours, and in 
experiment 13 for six hours, before the solutions were tested. 
The capacities of the two bottles which served for all the ex- 
