473 



were employed, but substituting folds of damp linen for the saucer of 

 sulphuric acid, so as fully to charge the air in the bell-glass with 

 vapour, the rotations rapidly rose from 4'0 to 17 or 18 per minute. 



But as the cold produced by the evaporation of the water in this 

 experiment might be a source of fallacy, an arrangement was made 

 to supply the bell-glass with air, previously charged with vapour, 

 formed at a distance of 5 feet from the glass. The rapidity of the 

 revolutions was however still considerably increased. 



Augmentation of the quantity of aqueous vapour, in the general 

 atmosphere of the room, by spreading wet cloths on the floor and 

 other parts, also produced increase in the rapidity of the rotations, 

 though to a small extent. 



These experiments* would seem to demonstrate that the ordi- 

 nary condition of atmospheric air within vertical tubes, open at both 

 extremities, is one of continual upward movement. 



If the atmosphere were a strictly homogeneous elastic fluid, and 

 in a state of perfect equilibrium, any portion of it contained in a 

 vertical tube would of course be perfectly stationary unless some 

 adventitious cause produced disturbance of its equilibrium. But 

 our atmosphere being a mixed fluid, and the aqueous vapour being 

 of a much lower specific gravity at all atmospheric temperatures 

 than the compound of which it forms a part, it is constantly rising 

 within a tube, as in the free air ; entering at the lower, and making 

 its exit at the upper orifice of the tube. 



The experiments appear further to demonstrate, that the presence 

 of aqueous vapour in the atmosphere is essential to the production 

 of the current within the vertical tubes, since by the abstraction of 

 vapour from the air by quicklime, the rotations of the discs were 

 invariably either diminished or caused to cease ; while on the other 

 hand, when the proportion of aqueous vapour in the air was in- 

 creased, the currents and the rotations of the discs were simulta- 

 neously accelerated. 



* Throughout the entire series the results were carefully observed during the 

 night, when the atmosphere of the room was free from solar influences. The dry- 

 and the wet-bulb thermometers yielded the same relative differences, and the discs 

 rotated with the same constancy. The night as well as the day observations were 

 continued through all the changes of temperature, from March 1853 to the present 

 time. 



