Oti the Nature of Ivfeiifihle Perspiration, with the Author s method 

 of computing the quantity of moijiure ivhich iff ues from the human 

 hodijy by that evacuation. 



11 AVI NG had a difcourfe with a certain medical gentleman on 

 the fubjeft of what is called Infenfible Perfpiration, or the great 

 quantity of matter or fubllance which ilfues from our bodies, and 

 which we are unconfcious of, 1 determined to make an experiment 

 on this fubject, by an obfervation of the perfpirable matter ifluing 

 not from my whole body, but from one of my hands only. 



For this purpofe, I took a glafs jar, wide enough to admit my 

 hand, which jar, as far as I knew, never had any thing put into it, 

 except clean rain water ; and having wiped it as dry and clean as I 

 could, I put my left hand into it, Hopping the aperture round my 

 wrift with a cloth, that none of the perfpirable matter might efcape 

 from the glafs, and I then began to drink tea until it not only 

 warmed me, but brought on a moderate perlpiration.^' 



After fome time had elapfed, I perceived the perfpirable matter 

 ilTuing from my hand, colledled on the inlide ot the glals, exhibiting 

 the fame appearance as when in fummer time, a bottle of wine is 

 brought out of a cool cellar into the warm air^ whereupon the 

 moirture in the air will condenfe and fettle on the glafs round the 

 wine. Soon after this, the moiflure was fo increafed, that it ad- 

 hered to the glafs in fmall drops, and at length thofe drops ran down 

 and fettled at the bottom of the glafs. After I had kept my hand 

 in this fituation three quarters of an hour, I took it out of the glafs, 

 and with all the accuracy I was able, I weighed the perfpirable 

 matter which had illued from it, and found it to be the fixtecnth 

 part of an ounce. 



In the latter end of the month of January, I repeated my obferr 

 vation, by again putting my hand, while it was A^ery cold, into the 

 glafs, and fitting down b\ the fire, I began to drink tea, fo hot and 

 fo plentifully, as to produce a copious perfpiration ; and after keep- 



