ON THE EXPANSION OF MOIST AIR* | SS 



ties, which are necessary consequences of this novelty in 

 meteorology. This method of examining the subject led supported by 

 me to use arguments,and to avoid experiments made by my- fgf a u b 7 y enlS ***" 

 self, as much as possible. The choice was suggested by 

 common prudence; for any person can form a correct judg- 

 ment of a syllogism; the value of which does not depend 

 on the character of the logician, but on qualities that are 

 apparent, and constitute its intrinsic merits or imperfections. 

 On the contrary when an experiment is described, we have Experiments 



no right to expect the reader will assent to the truth of it, |n certain en* 



. „ ., . • ... j less convinc* 



until he is convinced of the experimenter's abilities, and of ing. 



his candour too; which is very liable to suspicion in the 



course of a controversy. 



The preceding reasons determined me at the time to de- R eason f or re . 

 fer the experimental part of the refutation to a future op- curring to 

 portunity, in hopes, that some other person would under- c * tlt i jre * 

 take the task ; but the silence of both parties has hitherto 

 disappointed this expectation, and it almost obliges me to 

 publish certaiu experiments in my possession ; which in all 

 probability will place the controverted point in a clearer 

 light. If air and water be confined by a pellet of mercury 

 in a glass tube, closed at one end, and the apparatus be af- 

 terward raised to the boiling temperature, the new hypo- 

 thesis maintains, that the vapour of the water will make its 

 way through the pores of the permanent gasses, and counte- 

 ract the pressure of the atmosphere on the pellet of mercu- 

 ry, thereby leaving the included air at liberty to expand in- 

 definitely. The practical method of showing the truth of 

 this proposition by the manometer never appeared satisfac- 

 tory to me, in consequence of which I undertook to have 

 the experiments repeated in the following manner. 



Exp. 1. Barometer 30'06, a tube one twelfth of an inch Exp. 1. 

 in bore, and containing a quantity of water in the sealed 

 end, measured b| inches from the surface of the water to the 

 •pen end. A column of air T 4 ^ of an inch in length, or 

 something more than T V of the open space 6| inches, was 

 confined in contact with the water in the tube by a column 

 of mercury, | of an inch long, the temperature of the in- 

 strument being 46 . The open end of the manometer was 

 then fixed into the neck of a narrow bottle by means of a 



perforated 



