5© Mr. Henry on the Materiality of Heat, 



containing much water of cryftallization. The commonly 

 employed mode of afcertaining the fpecific caloric of bodies 

 is founded, therefore, en an alfumption which is deficient in 

 the charafter of a datum, and which itfelf requires proof. 



If thefe objeftions be valid, they will apply alfo to fliow 

 the fallacy ot the theorem, for finding the abfolute zero of 

 bodies. By this term fome philofophers appear to under- 

 iiand the point of abfolute privation of caloric, both free and 

 combined. I apprehend, however, that in ftri£l propriety it 

 can only be ufed to (ignify the negation oi uncoynhined caloric, 

 or, as Dr. Crawford expreffes himfelf, the point of abfolute 

 cold. As applied, however, to water, it is evident that the 

 whole quantity of heat is underftood. In afcertaining the 

 zero, fay thefe calculators, the capacity of ice to that of water 

 is as 9 to 10. It is plain, therefore, that when water freezes 

 it muft give out i-xoth of its whole heat; and this tenth part 

 is found to anfwer to 146" of Fahr. Confequently its whole 

 heat is ten times 146, or 1460°; and hence the natural zero 

 is 1460 — 32, or 1428°. Now of this eftimate it is a datum, 

 that the capacities of ice and water have precifely the above 

 ratio. But if the general formula for afcertaining the fpecific 

 caloric of bodies be founded on erroneous principles, it can- 

 not ferve as* the ground-work of any folid conclufions. 



The materiality of caloric may, I apprehend, be main- 

 tained, without admitting that we have made any fteps to- 

 wards detcrmhilng its quantity in bodies ; and the arguments 

 of Count Rumford and Mr. Davy are not demonllrative, 

 becaufe they affume that this part of the doftrine of caloric 

 cannot be relinquiflicd without abandoning it iji toto. I 

 may be permitted, therefore, to fiate my reafons for believing 

 caloric to be matter ; which would have been unnf ceflary 

 had the contrary been proved with all the force of -nathe- 

 matical denionliration. 



Avoiding all metaphyfical reafoningon the nature of mat- 

 ter, and aiTuming the generally received definition as fuffi- 

 cientlv characlcrizing it, I Ihall examine how far this ge- 

 neral charaAer of matter applies to the individual — caloric. 

 Caloric occupies fpace, or is extended, becaufe it enlarges the 

 dimenfions of other bodies; and, for the fame reafon, it is 

 impenetrable, fince, if it could exift at the lame lime in the 

 fame place with other bodies, their volume would never be 

 enlarged bv the addition of heat. Of form or figure, as only 

 a mode of extenfion, it is unneccflary to prove that caloric is 

 poflefled; and, indeed, there is perhaps only one general 

 quality of matter that will not be allowed it, viz. attraftion. 

 That caloric is influenced by the attudliou of gravitation, or 



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