5t)8 PHILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



not, these gentlemen can explain satisfactorily, and very probably in such a man- 

 ner as will throw other lights on the subject. 



It is also worthy of inquiry, whether all the amazing quantity of heat let 

 loose in these experiments was contained in the dephlogisticated air ; or whether 

 the greatest portion of it was. not contained in the phlogiston or inflammable 

 air. If it was all contained in the dephlogisticated air, the general rule is not 

 fact, that elastic fluids are enlarged in their dimensions in proportion to the 

 quantity of heat they contain, because then, inflammable air, which is 10 times 

 the bulk of dephlogisticated air, must be supposed to contain no heat at all ; 

 and it is known, from some experiments of my friend Dr. Black's, and some of 

 my own, that the steam of boiling water, whose latent and sensible heat are 

 only 1 100°, reckoning from 60°, or temperate, is more than twice the bulk of 

 an equal weight of dephlogisticated air. It seems however reasonable to sup- 

 pose that the great quantity of heat should be contained in the rarer fluid. 



It may be alleged, that in proportion to the quantity of phlogiston that is 

 contained in any fluid, the quantity of heat is lessened. But if we reason by 

 analogy, the attraction of the particles of matter to each other in other cases is 

 increased by phlogiston, and bodies are thereby rendered specifically heavier ; 

 and we know of no other substance besides heat which can be supposed to sepa- 

 rate the particles of inflammable air, and to endow it with so very great an 

 elastic power, and so small a specific gravity. On the other hand, if a great 

 quantity of elementary heat be allowed to be contained in inflammable air, on 

 account of its bulk, the same reasoning cannot hold good in respect to the phlo- 

 giston of phosphorus, sulphur, charcoal, &c. But all these substances contain 

 other matter besides phlogiston and heat. The acids in the sulphur and phos- 

 phorus, and the alkali and earth in charcoal, may attract the phlogiston so 

 powerfully that the heat they contain may not be able to overcome the adhesion 

 of their particles, till, by the effect of external heat, they are once removed to 

 such a distance from each other as to be out of the sphere of that kind of attrac- 

 tion.* If it be found to be a constant tact, that equal additions of phlogiston 

 to dephlogisticated air do not extricate equal quantities of heat, that may afford 

 the means of finding the quantities of heat contained in phlogiston and dephlo- 

 gisticated air respectively, and solve the problem. 



Many other ideas on these subjects present themselves ; but I am not bold 

 enough to trouble you, or the public, with any speculations, but such as I think 

 are supported by uncontroverted facts. I must therefore bring this long letter to 

 a conclusion, and leave to others the future prosecution of a subject which, 

 however engaging, my necessary avocations prevent me from pursuing. I cannot 



* On the -whole, this question seems to involve so many difficulties, that it cannot be cleared up 

 without many new experiments. — Orig. 



