330 RATIO OF .EVAPORATION TO HUMIDITY. 



and that the ^ n * ne nex * place I would observe, that, if we suppose 



contrary should the air to be driven back by the electric fluid gliding over 



take place if the 



supposition * ne Da "j tne effect should be the reverse of what takes 



were true. place: for, as this electric fluid acts with sufficient force 

 against the air to drive it back, and the little ball is very 

 moveable, the same thing should take place as with an 

 eolipile, sky-rocket, &c. The sky-rocket, for example, 

 ascends in the air only because the powder as it burns makes 

 a continual jet, which strikes and drives back the air with 

 great velocity. The air resists this rapid movement; and 

 the rocket, being movable is driven forward, and proceeds 

 with more or less rapidity. This is also the cause of the 

 kets, &c. 



III. 



Memoir on the Proportion the Evaporation of Water bears 

 to the Humidity of the Air. By Honore Flaugergues*. 



Humid ty of Jj)Y the humidity of the air should be understood the 

 cnces eyapora- proportion, that the quantity of water mingled and sus- 

 tion pended in a given quantity of air bears to the quantity of 



the air. The more humid the air, the slower and less con- 

 siderable the evaporation : and there is even a degree of hu- 

 midity, at which evaporation wholly ceases, because, the 

 air being loaded with all the moisture it can contain, no 

 Experiments more can rise. I have made a great number of experiments, 

 to ascertain the to ascer t a i n the. law, that this decrease of evaporation fol- 

 law of its ac- / -•,.,., 



t i on# lows; and as experiments of this kind appeared to me most 



proper to determine the general law of evaporation as it 

 respects the moisture of the air, I shall confine myself here 

 to those, on the results of which most dependance can be 

 placed, as I employed in making them an extensive appa. 

 ratus, of which the following is a description. 

 Apparatus de- I began with procuring a stock of air completely dried 

 for the purpose in a very dry season. I caused a cask to 

 be hooped and headed, that would contain about nine cubic 



* Journ. de Physique, vol. LXX ; p. 157. 



feet. 



