566 Onthe Force of Stcam or Vapour 
rallel, the one that was close being g inches long, 
and the other 96. Then conveyed two or three 
drops of ether to the end of the closed leg, and 
filled the rest-of the tube with mercury, except 
about 10 inches at the openend. This done, I 
immersed the whole of the short leg containing 
the ether into a tall glass containing hot water ; 
the ether thus exposed to a heat above the tem- 
perature at which it boils, produced a vapour 
more powerful than the atmosphere, so as to 
overcome its pressure and raise a column of mer- 
cury besides, of greater or less length accerding © 
to the temperature of the water. When the 
water was at 147° the vapour raised a column of 
35 inches of mercury, when the atmospheric 
pressure was 29. 75: so that vapour from ether 
of 147° is equivalent to a pressure of 64. 75 
inches of mercury; agreeing with the force of 
aqueous vapour of 257°, according to the pre- 
ceding estimation: in both cases the temperatures 
are 45° above the respective points of ebullition? 
In all the temperatures betwixt 102 and 147° 
the forces of ethereal vapour corresponded with 
those of aqueous vapour, as per table, betwixt 
212° and 257%. I could not reasonably doubt 
of the equality continuing in higher temper- 
atures; bnt the force increases so fast with the 
increase of heat, that one cannot extend the exe 
periments much farther without tubes of very 
,? 
