Chap. 5.] Experiments of .Bijhop Watfon* &c. 129 



cork and the water is not however a perfect vacuum j 

 it is occupied either by the vapour of the water, or by 

 a Frnall portion of air, or by both. Heat increafes the 

 elafticity both of air and vapour, and thus augments 

 the preffure upon the furface of the water, hence the 

 ebullition ceafes upon the application of the hot iron. 

 Cold, on the contrary, diminimes the elafticity of the 

 air, and condenfes vapour; and thus the preflure upon 

 the furface being leffened by the application of a cold 

 cloth, the ebullition of the water became more violent. 

 The heat of the water when it ceafed boiling was 

 130*. 



An experiment of another diftinguifhed philofopher 

 affords perhaps a better illustration of the whole theory 

 which has been juft advanced. This gentleman placed 

 a quantity of vitriolic ether under the receiver of an 

 air-pump, which was fo contrived that he was able to 

 let down a thermometer at pleafure, without admit- 

 ting the external air. He no fooner began to extract 

 the air, than the ether was thrown into a violent ebul- 

 lition, at the fame time its temperature funk furpriz- 

 ingly. When the ether was firft put in, its tempera- 

 ture was about 58% but it became fo cold when boil- 

 ing, that a quantity of water in a veflel contiguous to 

 it was fuddenly frozen. The manner in which thefe 

 phenomena may be explained is this : The weight of 

 the atmofphere being removed, the heat which the 

 ether contained was fufficient to make it boil. The 

 elementary fire which the ether loft in boiling was diC- 

 pofed of in forming a vapour more fubtile than the 

 ether itfelf; which could not, confiftently with the 

 principles eftablifhed, be formed without the abforption 

 of a considerable 'quantity of the matter of fire. Now 

 as it appears that water and fpirit of wine boil in va^uo 



* Chem. Effays, vol. iii. p. 162. 

 VOL. I. K at 



