608 PHILOSOPHICAL TRANSACTIONS. [aNNO 1775. 



impression of coolness to their nostrils, scorched just before by the hot air 

 rushing against them when they inspired. In the same manner their now cold 

 breath agreeably cooled tb.eir fingers whenever it reached them. On touching 

 his side, Dr. B. says, it felt cold like a corpse ; and yet the actual heat of his 

 body, tried under his tongue, and by applying closely the thermometer to his 

 skin, was 98°, about a degree higher than its ordinary temperature. When the 

 heat of the air began to approach the highest degree which this apparatus was 

 capable of producing, their bodies in the room prevented it from rising any 

 higher ; and when it had been previously raised above that point, inevitably sunk 

 it. Every experiment furnished proofs of this : toward the end of the first, 

 the thermometer was stationary : in the 2d, it sunk a little during the short 

 time they staid in the room : in the 3d, it sunk so fast as to oblige them to 

 determine that only one person should go in at a time : and Mr. Banks and 

 Dr. Solander each found, that his single body was sufficient to sink the quick- 

 silver very fast, when the room was brought nearly to its maximum of heat. 



These experiments therefore prove, in the clearest manner, that the body has 

 a power of destroying heat. To speak justly on this subject, it must be called a 

 power of destroying a certain degree of heat communicated with a certain 

 quickness. Therefore in estimating the heat which we are capable of resisting, 

 it is necessary to take into consideration not only what degree of heat would be 

 communicated to our bodies, if they possessed no resisting power, by the heated 

 body, before the equilibrium of heat was effected ; but also what time the heat 

 would take in passing from the heated body into our bodies. In consequence of 

 this compound limitation of our resisting power, we bear very different degrees 

 of heat in different mediums. The same person who felt no inconvenience 

 from air heated to 211°, could not bear quicksilver at 120°, and could just 

 bear rectified spirit of wine at 130°; that is, quicksilver heated to 120° fur- 

 nished, in a given time, more heat for the living powers to destroy, than 

 spirits heated to 130°, or air to 21 1°.* And they had, in the heated room 

 where their experiments were made, a striking though familiar instance of the 

 same. All the pieces of metal there, even their watch chains, felt so hot, that 

 they could scarcely bear to touch them for a moment, while the air, from which 

 the metal had derived all its heat, was only unpleasant. The slowness with 

 which air communicates its heat was further shown, in a remarkable manner, by 



* These numbers are the result of some experiments which were made on the first of February, in 

 a room where the heat of the air was ()'o°. Mr. Banks and Dr. Blagden found that tliey could bear 

 spirits which had been considerably heated and were then cooling, when the thermometer came to 

 Uie 130th degree; cooling oil at 129"; cooling water at 123°; cooling quicksilver at 117°. And 

 these points were pretty nicely determined ; so that though they could bear water very well at 

 123", they could not bear it at 125°, an experiment in which Dr. Solander joined them. And their 

 feelings with respect to all these points, seemed pretty exactly the same. — Orig. 



