[ 40 ] 



fome experiments (fee Sect. IV. and VL) ap* 

 peared to be chiefly a compound fait of the 

 vitriolic acid and volatile alkali, forming fal 

 vitriolatum ammoniacum this I procured in 

 the proportion of about i ■$ grain, in two ounces 

 of the moifture. 



From what appears to be the contents of the 

 city air, as above related, many particulars refult, 

 which may afford fome inlight into the nature 

 and caufe of the different difeafes in the city from 

 thofe without. There is reafon to prefume, 

 that putrid effluvia are noxious to animal 

 bodies \ they may very often introduce a fer- 

 ment into a fubject difpofed to the putrefactive 

 fermentation, and hence have a tendency to 

 promote difeafes which arife from a putrid 

 diathefis. 



But in populous cities, where prodigious 

 quantities of thefe effluvia are daily generated, 

 one might fufpect very fatal effects, fevers of 

 the moil dangerous kinds, more frequently to 

 occur. It may be here fuggefted from the fore* 

 going experiments, that a vitriolic acid is de- 

 tached from the coals burnt in this city, which 

 \miting with the volatile alkali from putrid 

 matters, may form a compound in no refpeft 

 injurious to the human machine. 



There appears from Experiment I. a material 

 circumftance, which, until very lately, we were 

 unacquainted with ; we find that from all fer- 

 menting vegetables a fixed air is detached, 

 which has fometimes proved a fudden poifon 

 to animals. The fame air is generated from 

 various fources, being exhaled from the earth, 

 3s well as rifes from all breathing animals ; and 

 |hpugh a certain proportion of it when difFufed 



in 



