160 ON THE AMOUNT OF CARBONIC ACID IN THE AIR. 



In comparing these results with the following deter- 

 minations of the carbonic acid contained in land air, it is 

 seen that the air of the Irish Sea contains a much smaller 

 proportion of carbonic acid than the air of the neighbour- 

 ing land. The most extensive observations on the land 

 air have given as means : — 



Observer. 



Locality. 



No. of 



Expts. 



Vols, in 

 10,000 of air. 



Th. de SaussurCj 



Chambeisy, 



104 



4-15 



Boussingault, 



Paris, 



142 



3-97 



Verver, 



Groningen, 



90 



4'20 



Roscoe, istser.. 



London&Manchester, io8 



3-97 



„ 2nd ser., 



Manchester, 



53 



3-92 



Smith, 



ditto. 



200 



4-03 



General mean of land air 4*04 



Mean of 26 expts. on sea air 3-086 



It would also appear that no difference is discernible in 

 the amount of carbonic acid in the air of day and night 

 over the Irish Sea. On the other hand, from Saussure's 

 observations a decided difference may be traced between 

 day and night air on the land — a conclusion subsequently 

 confirmed by several experimenters. 



In noting the above mean, 3 "08, and the apparent iden- 

 tity in the amount of carbonic acid in the air of day and 

 night over the sea, it should be borne in mind that July 

 and August are in general the hottest periods of the year 

 (these months were unusually hot this year, 1865), and 

 that consequently all the influences may be supposed at 

 work which would tend to increase the relative amount of 

 carbonic acid, and render appreciable any difference in the 

 air of night and day. 



The conclusions therefore to be drawn from these ex- 

 periments are : — 



I . That the influence of the sea in our latitudes in abs- 



