e 
in a Letter to Dr. Prieftley. Ist 
foda, and bole, (cinere, nitro, et cimolid,) for more effeCtually 
clearing their bodies from naftinefs when they bathed., I 
need not remark to you, that I employ the word ‘¢ nitre,”” 
Not in its ancient, but modern fenfe, 
It is highly defirabie that fome of our men, whofe opinions 
have weight with the public, would perufe the work of Lan- 
cifi, phyfician to Pope Clement XI, on the noxious exhala- 
tions of marfhes. (De Nox. Palud. Efflaviis.) By the per- 
fevering and luminous refearches of this great man, it was 
found, as long ago as the year 1716, that marfh-water, by 
fimple diftillation, (Jd7d. Lib. II. c. xii.) manifeited an acid 
quality ; and that calcareous {tones (Ibid. Lib. If. ¢.1i.) were 
better for paving the ftreets of cities than /liceous ones, be- 
caufe the alkaline nature of the former was adapted to imbibe 
the noxious moifture of the air, and fweeten the acid falts 
with which it abounded. Indeed, much of the matter des 
tailed by the writers.of our days on local fources of dif- 
tempers, may be found better obferved, and better ftated, by 
Lancifi, than in their writings. By the by I obferve he 
mentions the Englith philofopher Mayow, (Jdid. Lib. I, 
P. ii. cap. 2.) 
If the philofopher of Rome had reafoned upon his own 
' difcovery, he could not have failed to draw the inference, 
that by alkaline. fubffances might the HyDRA of peftilence 
_ be overcome.—As I have mentioned this moniter, I fhal] 
paufe a little to give you my opinion of the allegory among 
the ancients concerning her: and I attempt the explanation 
the more willingly, as I believe Lord Verulam has faid no- 
thing about it. The fable is this :—In Peloponnefus, between 
_Mycenz and Argos, there was a fen or marth of fome extent 
galled Lerna. This muddy and ffagnating pool was inhabited 
by Hydra, a horrible and devouring moniter with feveral 
heads ; fomé {ay feven, others nine, and others fifty. The 
gaalignity of her poifan was fugh that 2 wound from an ar+ 
Yow dipped into it was inftantly mortal. She made dreadful 
t 
; 
9 
a 
- 
. 
, 
havoc among the people of the furrounding country, and dez 
youred a great number of their fheep and other cattle. In 
obedience to the orders of the tyrant Euryfiheus, Hercules 
went to fight this deftructive and formidable creature. On 
hig 
