as a Vehicle for conveying Heat. 47 



mowed, in a manner perfectly clear and di ftinct, how thid 

 might be effected. Since that time this fcheme has fre- 

 quently been put in practice, with fucccfs, both in this coun- 

 try and on the continent*. Many attempts have likewife 

 been made, at different periods, to heat liquids by means of 

 fleam introduced into them; but mod of thefe have failed: 

 and, indeed, until it was known that fluids are nonconductors 

 of heat, and, confequently, that heat cannot be made to 

 defcendm them (which is a recent difcoverv), thefe attempts 

 could hardly fueceed ; for, in order to their being fuccefsful, 

 it is abfolutely neceffary that the tube which conveys the hot 

 fleam mould open into the lowefl part of the veffel which 

 contains the liquid to be heated, or on a level with its bot- 

 tom ; — but as long as the erroneous opinion obtained, that 

 heat could pafs in fluids in all directions, there did not ap- 

 pear to be any reafon for placing the opening of the fleam- 

 tube at the bottom of the veffel, while many were at hand 

 which pointed out other places as being more convenient 

 for it. 



But to fueceed in heating liquids by fleam, it is neceffary,, 

 not only that the fleam mould enter the liquid at the bottom 

 of the veffel which contains it, but alio that it fhould enter it 

 coming from nbove. The fleam- tube mould be in a vertical 

 pofition, and the fteam fhould defcend through it previous to 

 its entering the veffel, and mixing with the liquid which it 

 is to heat; otherwife, this liquid will be in danger of being 

 forced back by this opening into the fleam-boiler; for the 

 hot fteam, being fuddenly condenfed on coming into contact 

 with the cold liquid, a vacuum will necefiarily be formed in 

 the end of the tube ; into which vacuum the liquid in the 

 veffel, preffed by the whole weight of the incumbent atmo- 

 fphere, will rum with great force and with a loud noife; but 

 if this tube be placed in a vertical pofition, and if it be made 

 to rife to the height of fix or feven feet, the liquid which is 

 thus forced into its lower end will not have time to rife to 

 that height before it will be met by fleam, and obliged to 

 return back into the veffel. There will be no difficulty in 

 arranging the apparatus in fuch a maimer as effectually to 

 prevent the liquid to be heated from being forced backwards 

 into the fleam-boiler; and, when this is done, and fome 

 other neceffary precautions to prevent accidents are taken, 

 lleam may be employed with great advantage for heating 



* Although one fhould naturally imagine that the notoriety of thefe 

 fa&s would have been fufficient to prevent all attempts in our days to 

 claim a right to this invention, yet it is faid that a patent for it was taken 

 out only a few years ago. 



liquids, 



