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between 86° and 21°. But the fame quantityof caloric which would raife 262 parts of water65 degrees, would raife 119 parts 143 degrees;and the weight of the ice alone being 119, itfollows that during its liquefaction, heat isabforbed equivalent to 143 degrees of tempera-ture, and which can in no other way be accountedfor than by fuppofing it intimately combinedwith the water as it becomes liquid, and effentialto its ftate of liquidity.

The near correfpondence of this experimentwith the former, the one giving 140 and theother 143 degrees, is a convincing proof of thetruth of the general inference drawn from them;for this does not depend on minute obfervationwhere an inaccuracy of a degree or two or anyinequality of mixture will defeat the object ofthe experiment, but upon a large, palpable, andftriking difference which mult be obvious toevery obferver.

To fave the trouble of any calculation of pro-portion, this beautiful experiment may be madewith equal or with aliquot weights of ice andhot water. So if a lump of ice is dropped intoan equal weight of water heated to 200°, 140degrees of heat may be firft fubltracted fromthe hot water to counterbalance the liquefactionof the ice, and the real effect will therefore bethe fame as if water at 6o° and ice-cold water at3 2° were mixed in equal proportions, and ac-cordingly the heat of the mixture will be themean of 3 2° and 6o°, or 46°. If the hot waterbe twice the weight of the ice, only half thequantity (or 70 degrees) mult be fubftracted,and fo in proportion.

The general law deduced from thefe experi-ments, therefore, is that liquefaction alwaysdemands the addition of a great quantity ofcaloric beyond what the thermometer will indi-cate, and hence a fubftance during this changeabforbs caloric powerfully from all the fur-rounding bodies, and leaves them comparativelycold. Liquefaction is therefore a frigoriiic pro-cefs, and this difcovery explains the productionof cold and the theory of freezing mixtures ina great variety of inftances. Many of thefewill be mentioned after the oppofite procefs ofcongelation has been defcribed. Liquefactionat the higher temperatures is often termed fujion,thus we rather fay the fufton than the liquefactionof metals, or even of wax, fpermaceti, &c. But.in all thefe cafes an abforption of caloric alfotakes place, which is fhewn by preventing thefubftances from acquiring a higher temperaturethan their point of fulion, as long as a particleremains unmelted; or by reducing the tem-

perature of the melted fubftance immediately tothis point, when above it, if a piece of theunmelted body is thrown in. Thus q ladle fullof lead cannot be heated red-hot till all themetal is melted; and a quantity of red-hotmelted lead is direCtly cooled to the point offufion by the addition of folid lead.

Since caloric is abforbed during liquefaction,it follows that it mult be given out during con-gelation ; or, that not only the free thermo-metrical heat will be lowered to the congealingpoint, but that the latent caloric combined withthe liquid will alfo be expelled before con-gelation can take place. Similar experimentsto fome of thofe already defcribed, will there-fore apply (changing the circumftances) to thephenomena of congelation. Thus if a veffel ofwarm water is expofed to a very cold medium,the temperature is rapidly cooled down to thefreezing point, after which the water begins tocongeal. If kept in the fame fituation, caloricis abftra&ed as before, but the thermometricalheat now remains nearly the fame, till all thewater has loft its whole flock of combinedcaloric neceffary to fluidity, and is totally con-verted into ice, and it is not till after this periodthat the temperature begins again to fink asbefore. Alfo if ice, however cold (fuppofe ato°) be added to water at 3 2°, the eft'edt is tocongeal a portion of water, and the caloric givenout by the water in the procefs raifes the tem-perature of the ice to 3 2 0 . Therefore ice fwim-ming in water can never have a lower tempera-ture than 3 2 0 , and this point is fo invariable asto furnifh an excellent ftandard for the gradu-ation of thermometers.

Congelation therefore is as much a heating'procefs to the furrounding bodies, as liquefactionwas fhewn to be a cooling procefs. That is, thereduction of the temperature of any fubftanceto any given point below its freezing point ismuch retarded, if in the procefs it be neceffaryto convert a liquid body into a folid by theabftra&ion of caloric : for ice at 3 2° can muchfooner be cooled 10 degrees, than water at 32 0 ,the ice having only to furrender its free uncom-bined caloric, but the water having, in additionto this, to give up its latent caloric of fluidity.

The heating power of congelation with refpeclto the furrounding bodies, is generally to befhewn only by its retarding the rate of the cool-ing which thefe bodies would experience with-out the influence of this procefs. In a few .inftances however it is more ftrikingly lhewn byan actual rife of a thermometer immerfed influids at the moment of their congelation. The