COMPOSITION OF THE ATMOSPHERE. 39 



the carbonate of baryta precipitated. This is a laborious 

 process ; but, considering the great accuracy of the operator 

 and the long experience which he gained, we may place the 

 greatest confidence in his results. I am disposed to think 

 that there may be a little excess in his results ; but this 

 will not afiect the comparative amounts found at difierent 

 times, and which form the most interesting part of the 

 inquiry. He says^ : — 



" The quantity of carbonic acid in the open air in the 

 same place is subject to almost continual change, equally 

 with the temperature, the winds, the rain, and the atmo- 

 spheric pressure. The observations which I have made 

 since 1816 until the month of June of this year, in a 

 meadow at Chambeisy, three quarters of a league from 

 Geneva, indicate that the mean quantity of carbonic acid 

 in volume which 10,000 parts of air contain is equal to 5, 

 or more exactly to 4*9. The maximum of this gas is 6'2 ; 

 the minimum is 3*7. 



" The observations published {' Bibliotheque Univ.' vol.i.) 

 show as maximum in the same place a greater proportion of 

 acid ; but it is probable that this excess was the result of the 

 imperfection of the experiment. 



" The augmentation of the average quantity of carbonic 

 acid in summer, and its diminution in winter, are mani- 

 fested at different stations, — in the country as in the city, 

 upon the Lake of Geneva and upon a hill, in calm and dis- 

 turbed air. According to an average of thirty observations 

 made at Chambeisy, during seven years, with baryta- water, 

 the quantity of carbonic acid in the months of December, 

 January, and February, at midday, is to that of June, 

 July, and August as 77 to 100. 



" This ratio is not constant throughout every year. 

 There are times which form exceptions, and in which the 

 quantity of carbonic acid in summer is inferior to that in 

 * Annales de Ch. et de Ph. vol. xixviii., 1828. 



