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I. "On the relations between the Elastic Force of Aqueous Vapour, 

 at ordinary temperatures, and its Motive Force in producing 

 Currents of Air in Vertical Tubes." By W. D. CHOWNE, 

 M.D., F.R.C.P. Communicated by JOHN BISHOP, Esq. 

 Received March 15, 1860. 



(Abstract.) 



In 1853 the author of this communication made a considerable 

 number of experiments which demonstrated that when a tube, open 

 at both ends, was placed vertically in the undisturbed atmosphere of 

 a closed room, there was an upward movement of the air within the 

 tube of sufficient force to keep an anemometer of light weight in a 

 state of constant revolution, though with a variable velocity. An 

 abstract of the results of these experiments was printed in the ' Pro- 

 ceedings ' of the Society for June 1855. 



In order to further investigate the immediate cause or nature of 

 the force which set the machine in motion, the author instituted a 

 series of fresh experiments. 



These experiments were made in the room described in the former 

 communication, guarded in the same manner against disturbing 

 causes, and with such extra precautions as will be hereafter explained. 

 The apparatus used was a tube 96 inches long and 6 '75 inches 

 uniform diameter, the material zinc. The upper extremity was open 

 to its full extent; at the lower, the aperture was a lateral one 

 only, into which a piece of zinc tube 3 inches in diameter, and bent 

 once at right angles, was accurately fitted with the outer orifice 

 upward. Within this orifice, which was about 5 inches above the 

 level of the floor, an anemometer, described in the former paper, and 

 weighing 7 grains, was placed in the horizontal position. About 

 midway between the upper and the lower extremity of the tube, a 

 very delicate differential thermometer was firmly and permanently 

 fixed, with one bulb outside and the other inside, and the aperture 

 through which the latter was inserted completely closed. The scale 

 was on the stem of the outer bulb. 



The results of a long series of observations were recorded. The 

 state of the dry and the wet bulb of the hygrometer, as well as the 

 indications of the differential thermometer, was noted, in connexion 

 with the number of revolutions performed per minute by the ane- 



