refpetling Heat or Caloric. 121 



that none of it may efcape, and the heat will rife in it far 

 above 212 . Confine the fteam, and in it the heat will rife 

 juft as high as in the confined water; yet in the one the heat 

 exifts in a different ftate from what it does in the other ! ! — ■ 

 The remit, we fee, may be altered by mechanical contriv- 

 ances : nay, ftriclly fpeaking, What is the effect produced 

 by the almofphere but mere mechanical preffure ? Yet we are 

 to believe that a change has been effected in the phvjical 

 properties of one of the fubftances fubjecfed to its mechanical 

 operation! — Jf Nature had fo conftituted the atmofphere as 

 to have only half its prefent gravity, the point at which heat 

 would become latent, as it is called, in fteam would have been 

 far below 212"'. When water is made to boil in an exhaufted 

 receiver at a lower temperature, have we done any thing but 

 removed weight from its furface, and vice ver/a P — Does the 

 heat in the fteam in theie cafes pafs into a latent ftate alfo ? 

 If it does, the effect is mechanical : if it does not, then the 

 mere accident of the atmofphere being of irs prefent weight, 

 has nothing to do with the boiling point happening to fall 

 at 212 ! Eut he that would fay fo would be counted mad.. 



At Munich, and other places equally elevated above the 

 level of the fea, that is, having a lefs weight of atmofphere 

 upon them, water, in open veiiels, boils at 2oa\ In a par- 

 tially exhaufted receiver the fame effect takes place: and yet 

 the do&rme of latent heat is never confidered as inconfiftent 

 with the fact> really for no other renfon but becaufe a com- 

 mon thermometer cannot meafure fpecific heat. 



To demand that a thermometer fhould meafure the quan- 

 tity of heat poured into water to convert it into vapour, and 

 to maintain it in that form ; and to infift, becaufe the inftru- 

 ment will not do this, that the heat muft have changed its 

 nature, and loft its original character; is about as wife as it 

 would be to demand, that a pint meafure dipt into the ocean 

 mould determine the quantity of water in the latter, and to 

 infift that, otherwife, the water on the outfide of the veffel 

 muft have loft its original character, and be different from 

 that within : it is demanding that mercury, which, by its 

 conftitution, can at 212 only expand a certain quantity, 

 compared with its own bulk in fome given lower tempera- 



VOX...VIH. R ture, 



