696 PHILOSOPHICAL TRANSACTIONS.'i [aNNO 1775, 



about to all the different parts of the room, but standing still most of the time 

 in the coolest spot, near the lowest thermometer. The air felt very hot, but 

 still by no means to such a degree as to give pain : on the contrary, I had no 

 doubt of being able to support a much greater heat ; and all the gentlemen 

 present, who went into the room, were of the same opinion. I sweated, but 

 not very profusely. For 7 minutes my breathing continued perfectly good ; 

 but after that time I began to feel an oppression in my lungs, attended with a 

 sense of anxiety ; which gradually increasing for the space of a minute, I thought 

 it most prudent to put an end to the experiment, and immediately left the room. 

 My pulse, counted as soon as I came into the cool air, for the uneasy feeling 

 rendered me incapable of examining it in the room, was found to beat at the 

 rate of 144 pulsations in a minute, which is more than double its ordinary 

 quickness. To this circumstance the oppression on my breath must be partly 

 imputed, the blood being forced into my lungs quicker than it could pass through 

 them ; and hence it may very reasonably be conjectured, that should a heat of 

 this kind ever be pushed so far as to prove fatal, it will be found to have killed 

 by an accumulation of blood in the lungs, or some other immediate effect of an 

 accelerated circulation ;* for all the experiments show, that heating the air does 

 not make it unfit for respiration, communicating to it no noxious quality except 

 a power of irritating. In the course of this experiment, and others of the 

 same kind by several of the gentlemen present, some circumstances occurred to 

 us which had not been remarked before. The heat, as might have been ex- 

 pected, felt most intense when we were in motion ; and, on the same principle 

 a blast of the heated air from a pair of bellows was scarcely to be borne; the 

 sensation in both these cases exactly resembled that felt in our nostrils on inspi- 

 ration. The reason is obvious ; when the same air remained for any time in 

 contact with our bodies, part of its heat was destroyed, and consequently we 

 came to be surrounded with a cooler medium than the common air of the room ; 

 whereas when fresh portions of the air were applied to our bodies in such a 

 quick succession, that no part of it could remain in contact a sufficient time to 

 be cooled, we necessarily felt the full heat communicated by the stove. It was 

 observed that our breath did not feel cool to the fingers unless they were held 

 very near the mouth ; at a distance the cooling power of the breath did not suf- 

 ficiently compensate the effect of putting the air in motion, especially when we 

 breathed with force. 

 - A chief object of this day's experiments was, to ascertain the real effect of 



• Since this experiment, I have observed the mucus from my lungs to be more serous than before, 

 and to incline more to a saltish taste, though the lungs themselves seem perfectly sound in all other 

 respects ; which raises a suspicion that some of the smaller arteries suffered a degree of dilatation from 

 the increased impulse of the blood. — Orig. 



