2(58 ON THE FORCE OF STEAM OR VAPOUR 



range, namely from 142° to 212° : the vapour from etlier 

 deprefles the mercury about fix inches in the temperature 

 of 32°. 

 above ebullition Finding that ether below the point of ebullition agreed with 

 water below the faid point, I naturally concluded that ether 

 above the point would give the fame force of vapour as water 

 above it ; and in this I was not difappointed ; for, upon trial 

 it appeared that what I had inferred only from analogical 

 reafoning refpeding the force of aqueous vapour above the 

 boiling point, adually happened with that from ether above 

 the faid point. And ether is a much better fubjed for expe- 

 riment in this cafe than water, becaufe it does not require fo 

 high a temperature, 

 with the fyphon I took a barometer tube of 45 inches in length, and having 

 baiometer. fealed it hermetically at one end, bent it into a fyphon fliape, 



making the legs parallel, the one that was clofe being nine 

 inches long, and the other 36. Then conveyed two or three 

 drops of ether to the end of the clofed leg, and filled the 

 reft of the tube with mercury, exxept about 10 inches at the 

 open end. This done, I immerfed the whole of the lliort 

 leg containing the ether into a tall glafs containing hot water ; 

 the ether thus expofed to a heat above the temperature at 

 which it boils, produced a vapour more powerful than the at- 

 mofphere, fo as to overcome its preffure and raife a column 

 of mercury befides, of greater or lefs length according to 

 the temperature of the water. When the water was at 

 147° the vapour raifed a column of 35 inches of mercury, 

 when the atmofpheric prelTure was 29.75 : fo that vapour 

 from ether of 147° is equivalent to a preffure of 64.75 

 inches of mercury ;'*agreeing with the force' of aqueous 

 vapour of 257°, according to the preceding eflimation : in 

 both cafes the temperatures are 45° above the refpedive 

 points of ebullition. In all the temperatures betwixt 102° 

 and 147° the forces of ethereal vapour correfponded with 

 thofe of aqueous vapour, as per table, betwixt 212° and 

 257°. I could not reafonably doubt of the equality con- 

 Experiments in tinuing in higher temperatures ; but the force increafes fo 

 which the re- £^^ ^jjj^ ^l^g increafe of heat, that one cannot extend the 



action or in- 

 cluded air was experiments much farther without tubes of very inconve- 



ufed as the mea- j^i^nt lengths. Being defirous however to determine the 

 fure of force. o - o • 



force 



