70 ON HEAT. 



perature, whe- which is extremely probable, a hot body expofed to cool in a 



foalfcrT C c ^ e place, or Cur rounded on all fides by walls, ought to cool 



with the tame celerity, or in the lame time, whatever may be 



the magnitude of this enclofure, provided the temperature of 



Thcfefaflscon- fa e f lc j es or vva |j s b c at a con ft an t given temperature; and the 



firm that truth 5 « r . ,. , , , & . ., , ! ,.,,,, 



reiuKs ot the experiment here delcribed, in which the hot 



body was enclofed in a veflel of a few inches diameter, com- 

 pared with thofe of feveral experiments made laft year, in 

 which the heated bodies expofed to cool between the walls 

 of a large-chamber, appear to confirm this conclufion. 

 and that the air As to lne e ff e ^ placed bf the air in cooling a heated 

 body expofed to cool in a clofe place filled with that fluid, I 

 have reafon to believe that it is much lefs confiderable than 

 has been fuppofed. 

 Former experi- I have (hewn by direct and conclusive experiments, that 

 that lVrTcdves Doc ^ es co °l ar) d are heated, and that with confiderable cele- 

 oniy 1.27th rity, when placed in a fpace void of air * ; and, by experi- 

 pdrt * ments made laft year with the intention of clearing up this 



point, I Found reafons to conclude, that when a hot body 

 cools in tranquil air not agitated by winds, one twenty-feventh 

 only of the heat loft by this body (or to (peak more coreclly, 

 which it excites in furrounding bodies) is communicated to 

 The reft partes the air, all the reft being carried to a diftance through the 

 y u ja ion. & .^ ^^ communicated by radiation to the furrounding folid 

 bodies. m 



.-* *.. 



Sect. II. Experiments on cooling Bodies, 



It is only by careful obfervation of the phenomena which 

 accompany the heating and cooling of bodies, that we can 

 hope to acquire exact notions of the nature of heat and its 

 manner of acting. \ ^ M< 



Condufting Many experiments have been made by different perfons at 



witlhre^ardto 8 different times, with a view to determine what has been 

 heat. called the conducting quality of different fubftances with re- 



gard to heat: I have myfelf made a confiderable number; 

 and it is from their refults, often no lefs unexpected than in- 

 terefting, that I have been gradually led to adopt the opinions 

 on the nature of heat which I h^e prefumed to fubmit to the 

 judgment of this illuftrious aflembly. The flattering attention 



* See my Memoir on Heat in the Philofophical Tranfa&ions for 

 1786, and in my eighth Eflfay. 



with 



