the seveP4ilGas€9'in'tli^4^mosphere. 253 



This I have repeated nearly In his manner, and 

 found a similar result. But the table he has 

 given us of aqueous vapour at other tempera- 

 tures is very far wrong, especially at tempera- 

 tures distant from 64*.-^The numbers were 

 not the result of direct experiment, like th§ 

 one above.— If we could obtain the tempe- 

 ratures of all parts of the earth *s surface, for 

 any given time, a mean of them would pro- 

 bably be 57° or 58°. Now if we may suppose th0 

 force of vapour equivalent to that of 55°, at a 

 medium, it will, from the table, be = to .44-3 

 of mercury ; or, nearly yV of the whole atmo- 

 sphere. This it will be perceived is calculated 

 to be the weight of vapour in the whole at- 

 mosphere of the earth. If that incumbent over 

 any place at any time be required, it may be 

 found as directed above. 



3. 0/ the weight of the Carbonic Acid 

 Atmosphere. 



From some observations of Humboldt, I was 

 led to expect about ^^-^ part of the weight of 

 the atmosphere to be carbonic acid gas : buf I 

 soon found that the proportion was immensely 

 over-rated. From repeated experiments, all 

 nearly agreeing in their results, and madc;at 



