1798: ] fn Experiment on. the 
the- preface, that this will, m a fhort 
time, be fuperfeded by a-more complete 
edition ; in this cafe, rhe purchafers of 
the prefent, if they wifh, as moft men 
do, to have a perfect work, will probably 
be obliged to pay a guinea for the whole, - 
in three volumes, and may perhaps lofe 
feven fhillings by the firft edition. 
- I mean not more particularly to point 
out Dr. RoL_io as blameable in this 
refpeé& ;-feveral other authors are, in my 
opinion, fully as much fo as he is. I have 
alluded to his book, becaufe it has more 
immediately ftruck me as muchtoo {plen- 
did for general ufe, bur | by no means with 
‘to be underftood as centuring hiny alone, 
Let works cf tafte and ftandards of ex- 
cellence, purchafed by the rich and mag- 
nificent, be published with every embel- 
lifhment and elegance that art can be- 
ftow, but let works, intended for general 
utility and propofed, improvemeuss, be 
contented to appear im a more humble 
drefs, and ata price which may not abto- 
jutely deter the unopulent philofopher 
from fearching into them for wifdom. 
September 22. 5. M. 

For the Monthly Magazine. 
Ax EXPERIMENT ON THE CONGELA- 
TION CF MERCURY.MADE BY Citt- 
ZENS HassenrRATZ, WELTER, 
Ronjour, AND HACHETTE. 
£ hang nitric acid that was to ferve for 
the operation was firft prepared ; 
for that purpole, acid was taken of which 
the {pecific gravity was 1.526, and this 
was\ mixed with a certain quantity of 
fnow, at the temperature of the atmof- 
phere, which occafioned a production of 
heat. Succeflive dofes of {now were af- 
terwards added, till heat was no jonger 
produced. The acid was then reduced 
to the fpecific gravity of 1.420, and was 
of the fame temperature as the atmof- 
phere. i 
After this preparation, a mixture was 
made of three parts of fnow, and one of fea 
falt, containing its water of cry ftallization, 
the temperature of the atmo{phere being 
9° (of Reaumur’s thermometer). By thefe 
means a degree of cold of 17° was ob- 
tained. 
It was obferved that this temperature, 
refulting from the mixture, did not 
change during three days, though that 
of the atmofphere varied from 5? above 
nought to 9° bélow; nor did the mixture 
take the temperature of the atmofphere 
till the {alt was entirely diffolved. 
_ This fecond mixture being made, two 
little glafs pails, one full of fow, the 
~ 
Congelation of Mercury 29 
other of witric acid, prepared im the man- 
ner indicated abeve, were plunged into 
it, and in half an hour cook the tempe- 
rature of the mixture, thatis to fay, 17°; 
but the fhow had not quite reached th 
fame degree of cold. By means .of a 
tn and, {ome of this {now was gradually 
introduced into the pail containing the- 
nitric acid; and the mixture, which bad a 
thermemeter of {pirits of wine plunged 
into it, was carefully ftirred about. The 
thermometer fell gradually, in a manner 
perceptible to the eye, till, in about 
eight or ten minutes, it reached 31°. 
The mercury, inclofed in very thin bulbs 
of glafs, was then plunged into the mix- 
ture alfo, and became perfe€tly folid. The 
perton who held the glafs tube belonging 
to, the bulb, thought he perceived the 
moment of the change, by a flight thock 
which his hand underwent, and which 
may have been occafioned by the fudden 
contraction of the* mercury; a pheno- 
meénon fimilar to what is obferved when 
phofphorus pafies from a liquid to a folid 
fiate, It was alfo perceived that a por- 
tion of the metal was cryftallized. 
The folidity of the mercury was after- 
Wards aicerrained by beating it upon a 
flat plate (uz tas) with a hammer, both 
cooled in the fecond mixture, that is to 
fay, at the temperature of 17° : by this 
operation ic was confiderably flattened. 
One of the experimen-ers took: im-his 
hand fthe metal thus flattened, and fill 
folid, and, keep'ny it there for fome 
time, felt a painful. fenfation, fimilar to 
that of a burn. The mercury left a 
white merk, which afterwards turned 
red; and was’ perceptible ‘for feverel 
days. 
It was remarked that, at the tempe- 
rature of 31°, the addition of more fhow 
did not increafe the cold; but, on the 
contrary, diminifhed’it by a production 
of heat; the moment of its doing fo was 
eafily determinable, becaufe the fnow 
then fwam upon the acid, in the form’ of 
little icicles. 

To the Editor of the Monthly Magazine. 
SIR, 
spe following declaration lately fent 
to a friend for his fignature, in or- 
der to qualify him for receiving a part of ° 
a legacy left by an opulent Diffenter, 
not long fince deceafed, afforded me at 
the fame time amufement and concern. 
“« J —— of —— do hereby declare, 
“ that I am a Minitter, Teacher, and 
‘““Preacher of the Gofpel 5 that I am not 
‘an Unitarian, Arian, Socinian, or 
“© Arminia’ 
