RATIO OF EVAPORATION TO HUMIDITY. 



331 



feet, very clean, and the staves and heads of which were 

 perfectly dry. I luted the joints accurately; and for 

 greater precaution pasted over them slips of paper, to pre- 

 vent all access of the external air. Into the bung-hole of this Preparation of 

 cask I poured about two cubic feet of quicklime coarsely 

 powdered, and hot from the kiln. The bung-hole was 

 then closed with a very tight straight cock, the key of 

 which was perforated with a hole about three lines in dia- 

 meter. In this state I left things about three weeks, shak- 

 ing the cask several times a day, that the lime might present 

 fresh surfaces to the contact of the air, and thus more 

 speedily and completely free it from all the water, that 

 might be suspended in it. Thus presuming the air to be 

 perfectly dried, I employed it in my experiments, pouring 

 it into a tin vessel, which I had made for the purpose. 



This vessel consists of a hollow cylinder, 13 in. 2 lines * Vessel for 

 in diameter, and 18 inches high. This cylinder is closed m e ^jjf u £ e ex ° 

 at one end by a circular plane, and at the other by a cone 

 3 in. 7 lines high. Its capacity is about 2614 cub. in. 

 The summit of the cone is truncated; and has soldered to 

 it a small cylindrical tube, capable of receiving a cylindri- 

 cal vessel of glass, four lines in diameter, intended to hold 

 the water to be evaporated into the air in the vessel. This 

 glass is fixed in the tube by means either of putty or .of 

 soft wax. The tin vessel may be fixed in a perpendicular 

 position, with the glass vessel downwards, by means of 

 two handles soldered to the cylindrical part, and resting 

 on two supports of iron fixed upright on a table. The 

 sheets of tin, of which this instrument is made, are very 

 carefully soldered ; and the external air cannot find admit- 

 tance, except through the aperture of the tube at the sum- 

 mit of the cone when this is not closed by the glass vessel. 

 To fill this vessel with the dry air in the cask, I began by Mode of filling 

 filling it completely with fine sand, perfectly dried by a fire. vesse1, 

 I then placed it on the cask, so that the aperture at the 

 end of the conical part was exactly fitted to the cock; and 3 

 after carefully closing the juncture with soft wax, I turned 

 the key of the cock. The sand, escaping by the hole in 



* The French measures are here retained. C, 



the 



