320 Danreli on a new Hi/giomeler. 



condensation at 50°- I then took a receiver, fitted with a hy- 

 grometer, whose capacity was fifty-six cubic inches, and ground 

 to the plate of the air-pump. The condensation was produced 

 very visibly under the glass at the same temperature. Now, 

 the quantity of vapour in a cubic foot of the air, under the 

 above conditions, was only 4.1 16 grains; therefore, the quan- 

 tity actually included in the receiver, could only be 0.133 

 grains, which will serve to prove the extreme delicacy of the 

 uistrument, as it distinctly indicated so small a quantity. The 

 receiver was then slid over a vessel containing water. In an 

 hour and a half, the external temperature remaining the same, 

 the precipitation took place at 57°. At the expiration of another 

 hour and a half, the affusion of the ether upon the exterior 

 ball caused instantaneous condensation upon the interior, 

 shewing that saturation at the existing temperature had taken 

 place. The bell-glass was now slid from the water without 

 • changing its contents, and placed over a glass, containing a 

 few drops of sulphuric acid. After remaining a quarter of an 

 hour in this situation, a depression of temperature of 30° pro- 

 duced no mist upon the instrument. 



Exp. 2. The receiver was placed upon the plate of the air- 

 puihp, with some water under it. The air was then exhausted 

 as perfectly as possible. The b.aiometer stood at 29.79, the 

 thermometer at 62°, the gauge of the pump at 29.20 ; to the 

 latter should be added, the pressure of the included vapour, at 

 62° — 0.560, which would make the gauge and the barometer 

 correspond within 0.03. When ether was dropped upon the 

 exterior ball, ptrecipitation was instantaneous. Air was now 

 admitted gradually till the gauge fell to 14. The point of con- 

 densation was not altered, neither was it affected by restoring 

 the equilibrium completely. 



Exp. 3. Temperature 64°, point of condensation 61°. The 

 air in the receiver was rarefied till a copious cloud was formed. 

 The gauge then stood at .8.1, the point of condensation had 

 fallen to 54°. When the glass had risen to 60°, the air was 

 suddenly restored, and a copious dew was formed upon it ; the 

 exhaustion was next carried on till the cloud had totally disap- 



