afirihtd lo Heat. ggg 



to touch the glafs. I likewife avoided, upon all occafions, and particularly in the cold 

 room, coming near the balance with my breath, or touching it, or any part of the ap- 

 paratus, with my naked hands. 



Having determined that water does not acquire or lofe any weight, upon being 

 changed from a ftate oi Jludity to that of ic<, and vice verfa, I (hall now take my final 

 leave of, a fubjeft which has long occupied me, and which has cod mc much pains and 

 trouble ; being fully convinced, (from the refults of the above-mentioned experiments, J 

 that if heat be in faft a fuhjlance, or matter,— a fluid fid generis, as has been fuppofed, 

 which, paffing from one body to another, and being accumulated, is the immediate 

 caufe of the phaenomena we obferve in "heated bodies, (of which, however, I cannot 

 help entertaining doubts,') it muft be fomething fo infinitely rare, even in its mofl con- 

 denfed flate, as to baffle all our attempts to difcover its gravity. And, if the opinion 

 which has been adopted by many of our ableft philofopheri, that heat is nothing more 

 than an inteftine vibratory motion of the conftituent parts of heated bodies, fliould be 

 well founded, it is clear that the weights of bodies can in no wife be afFefted by fuch 

 motion. 



, It is, no doubt, upon the fuppoJition that heat is a fubllance diflinft from the heated 

 body, and which is accumulated in it, that all the experiments which have been under- 

 taken, with a view todetenniije the weight which bodies have, been fuppoled to gain, or 

 lofe, upon being heated or cooled, have been made ; and, upon this fuppofition (but 

 without, however, adopting it entirely, as I do not conceive it to be fufficiently proved,) 

 all my refearches have been direfted. 



The experiments with affl^^r, and with /<:<?, were made ina'manner which I take to be 

 perfeftly unexceptionable ; in which no foreigjh caufe whatever could affeft the refults 

 of them ; and the quantity of heat which water is known to part with, upon being frozen, 

 is fo confiderable, that if this lofs has no efleft upon its apparent weight, it may bd^re- 

 fumed that we (hall never be able to contrive an experiment by which we can render the 

 weight of heat fenfible. 



Water, upon being frozen, has been found to lofe a quantity of heat amounting to 

 140 degrees of Fahrenheit's, thermometer; or, which is the fame thing, the heat 

 which a given quantity of water, previoufly cooled to the temperature of freezing, 

 aftually lofes, upon being changed to ice, if it were to be imbibed and retained by an 

 equal quantity of water, at the given temperature, (that of freezing,) would heat it 140 

 degrees, or would raife it .to the temperature of (32° -{-140) 172° of Fahrenheit's 

 thermometer, which is only 40° fhort of that of boiling water ; confequently, any given 

 quantity of water, at the temperature of freezing, upon being aftually" frozen, lofes 

 almoft as much heat as, added to it, would be fufEcient to make it boil. 



It is clear, therefore, that the difference in the quantities of heat contained by the 

 Vol. III.— December 1799. 3E water 



