f 9 1 ] 
of philofophiqal inquiry, which they difcover. 'Jfhey 
appear to mg to contain many new, curious, and 
valuable obfervations ; but one of the concjufions, 
which he draws from his experiments, I am fat if- 
fed, from my own obfervations, is ill founded, and 
from the nature of it, muft be dangerous. I mean 
his maintaining, that there is nothing to be ap- 
prehended from the neighbourhood of putrid 
marfh.es . 
I was particularly furprized, to meet with fuch 
an opinion as this, in a book infcribed to yourfelf, 
who have fo clearly explained the great mifchief 
of fuch a htuation, in your excellent treatife on 
the difeafes of the army. On this account, 1 have 
thought it not improper, to addrefs to you the fol- 
lowing obfervations and experiments, which I 
think clearly dernonftrate the fallacy of Dr. 
Alexander’s reafoning, indifputably eftablifh 
your dodtrine, and indeed juftify the apprehenlions 
of all mankind in this cale. 
I think it probable enough, that putrid matter, 
as Dr. Alexander has endeavoured to prove, will 
preferve other fubftances from putrefaction ; be- 
caufe, being already faturated with the putrid 
effluvium, they cannot readily take any more ; but 
Dr. Alexander was not aware, that air thus load- 
ed with putrid effluvium is exceedingly noxious 
when taken into the lungs. I have lately, however, 
had an opportunity of fully afcertaining how very 
noxious fuch air is. 
Happening to ufe at Caine, a much larger trough 
of water, for the purpofe of my experiments, than 
I had done at Leeds, and not having freffl water 
N 2 fo 
