69 
Steam Engine. 
as per table, betwixt 212 degrees and 257 degrees. I 
could not reasonably doubt of the equality continuing in 
higher temperatures ; but the force increases so fast with 
the increase of heat, that one cannot extend the experi- 
ments much farther without tubes of very inconvenient 
lengths. Being desirous however to determine the force 
of the ethereal vapour experimentally up as high as 212°, 
I contrived to effect it as follows:— Took a syphon tube, 
such as described above, only not quite so long, and fiii- 
ed it in the manner above mentioned, with ether and mer- 
cury, leaving about ten inches at the top of the tube va- 
cant ; then having graduated that part into equal portions 
of capacity, and dried it from ether, I drew out the end of 
the tube to a capillary bore, cooled it again so as to suffer 
the internal atmospheric air to be of the proper density, 
and suddenly sealed the tube hermetically, thus inclosing 
air of a known force in the graduated portion of the tube. 
Then, putting that part of the tube containing ether into 
boiling water, vapour was formed v/hich forced the mer- 
curial column upwards and condensed tlie confined air, 
till at length an equilibrium took place. In this way I 
found 8.25 parts of atmospheric air of the force 29.5 were 
condensed into 2.00, at the same time a perpendicular 
column of 16 inches of mercury in addition pressed upon 
the vapour. Now the force of elastic ffoids being inverse- 
ly as the space, we have 2.00 : 29.5 : : 8.25 : 121.67 
inches == the force of the air within; to which adding 16 
inches, we obtain 137.67 ~ thevvhole force sustained by 
the vapour, measured in inches of mercury. The force 
of aqueous vapour, at the same distance beyond the boil- 
ing point, or 322°, is equal to 137.28, per table. Thus 
it appears that in every part of the scale on which experi- 
ments have been made, the same law of force is observa- 
ble with the vapour of ether as of water. 
