‘well as “« hydra, 
in a Letter to Dr. Priefiley. 153 
century, wants a Hercules, This interpretation is confirmed 
by another confideration, that the ancients had not only 
their Hydra, who lived in the water, but their Cher/ydra, 
who remained afier the marth or fen was dried up. Cher- 
frdra, being derived’ from the two words, xpc0s, land not fit 
for the plough; and viex, the monfler of the fens; will thus 
mean the venomous and fickly condition of the neighbouring 
atmofphere after the water was exhaled, and the ground at 
the fame time not renderéd arable thereby, typified by a poi- 
fonous ferpent: and was thus expreffive of the rage of pefti- 
lential effuvia, which fometimes, and under certain circum- 
ftances, continue in a virulent a in dry weather, near 
their dried fources. 
Hydra is feemingly mentioned by Virgil (4En, vi. v. 576.) 
‘as 2 fictitious or poetical animal. Bathent, however, with his 
‘uiual prodigious erudition, appears defirous to make the whole 
ftory literally intelligible. (Hierozoici pars pofter. Lib. III. 
cap, xiti.)" But Lancifi, with a more clear and difcriminating 
mind, perceives that important phyfical truths are doricealal 
ander this two-fold allegory, and fhews how they are to be 
unriddled. (De Nox. Palud. Eff. Lib. IL. p. 1. cap. 3.)— 
Jn confidering thefe matters you will not fail to recolleé that 
the claffical writers, and others, ufe the word ‘ hydrus’’ as 
” and fome of them apparently confound 
the two. The former noun of the mafculine gender is pro- 
bably the name of the real animal, the water-/nake, the 
Jatter of the mnaginary one.—But of this enough. 
If peftilential matter, as I obferved before, can be fubdued’ 
by alkalies, then the formation of feptite of pot-afh in the 
‘alimentary canal mu(i be a very frequent and common pro- 
eefs. It is univerfally agreed that peftilential matter may be 
taken into the flomach by fwallowing; and no reafonable 
doubt can be entertained of its production within that organ, 
_and other parts of the intefiinal tube, from the corrupted re- 
mains of food. The whole tenor of prefcription, as explained 
_in my letter concerning the ufe of alkaline remedies in fevers, 
(1 Medical Repof. p. 265.) goes to fhew that the offending 
-eaufe is of an acid quality: and in its worft forms, I think 
_he acid engendered has fepton for its bafis; fince aliment, 
Vou. V. X containing 
