#14 
both thermometers were noted, the fpirits 
ftood the higheft: it was only in 6 in- 
ftances that the variations either way ex- 
ceeded 3%, in general they were much le‘s. 
ath. At the hour of 6.—17 times the 
two thermometers coincided ; 22 times 
the mercury ftood the higheft, and in aijl 
the remaining 213 obi/ervations of both 
thermometers at this hour, the fpirits 
ftocd the higheft; on the roth Sept. and 
sth Ogtober, this difference amounted to 
4°; on the 3d April to 32°; on &th 
May, and 16th Sept. to 32°; on art 
June, 28:h Auguft, 13th Oétober to 3°; 
on 23d May, 15th Auguf, and sth Sep. 
tember to 23°; on 4th, 27th and 28th 
April, rrth and 26th May, r7th June, 31ft 
July, gth and 15th September to 23°, 
sth. At the hour of 9 P. M.—x1 times 
the two thermometers coincided ; 8 times 
the mercury ftood the higheft (feldom 
more than 1°) and in all the remaining 
¥16 obfeivations, in which both thermo- 
meters were no'ed, the fpirits ftood the 
highelt; this difterence amounted on the 
zoth June to 43°; on the 26th June to 
44°; on 19th May to 4°; on rsth July 
r~ 
wie 
to 33°5; on 17th June to 3$°3 on roth 
‘June, and 7th July to 34°53 on 2oth 
May, 27th June, and 13th July to 3°, &c. 
6th. The x2th December, was the 
only day in my journal, wherein the mer- 
cury always ftood higher than the fpirits, 
which with the 8th September, and 2d, 
sth and 21ft January were the only days, 
in which the fpirits were not at fome 
hour of obfervation, higher thin the mer- 
cury; during 19 days, the fpirits were 
higher at every hour of obfervation than 
the mercury ; and in 21 other days, they 
coincided in the firft part of the day, 
and the {pirits were afterwards the higheft : 
the two thermometers did not coincide 
during any one day. 
7th. The greateft height of the mer- 
cury, which was noted during the above 
interval, was 852°; on the 28th June, 
1801, at oh A. M. and the Jowelt was 
12°, on the r2th January 1802, at 12 
o'clock P. M. 
From the above it muft IT think be evi- 
dent, that fpirit thermometers are unfit 
for meteorological obfervations, or any 
ether where the heat is liable to fudden 
variations. It would, however, be of 
ufe'to have a fpirit thermometer attached 
to’ the fame plate wich the mercurial 
thermometer intended for ufe, and having 
lines drawn acrofs from each degree on 
one thermometer to the correfponding de- 
gree on the other thermometer, for readily 
noting whenever the mercury was ob- 
ferved, whether the fpirits flood higher 
or lower, and how many degrees; which 
would indicate any recent and confider- —3. Oil for making pictures in the chae 
Authenticity of Chaucer's Portrait. 
[ April 1, 
The convexity of the top of the mer- 
cury in a barometer tube, fhews when 
the mercury therein is rifing, and its con- 
cavity when it is falling; and it is de- 
firable that thofe who regularly note the 
ftate of the barometer at’ certain hours, 
would by the fign + and —, or fome 
other marks after each obfervation, de- 
note this rifing or falling ftate of the 
mercury: and in like manner, by the 
help of an attached fpirit thermometer, 
denoting the riling or falling ftate of the 
mercury in the thermometer, this alfo 
might be fet down; and it might have 
its ufe alfo, to ftate all the confiderable. 
differences between the mercury and the 
{pirits, as I have done above. 
Yours, &c. Joun Farey, 
12 Crown fireet, Wefiminfler, 
15 February, 1804. 
Fo the Editor of the Monthly Magazine. 
SIR, 
SHE Letter of Count Truchfefs, in 
I your laft, conveyed to my mind fuch 
thorough fatisfaction in regard to the au. 
thenticity ot Chaucer’s portrait, that, did. 
I not think an acditiona! remark or two 
might firengthen iis teltimony to thofe 
who may ftill be fcrupulous, I would cers 
tainly withhold my obfervations. ; 
The great difficulty feems to be, whe- 
ther this portrait, painted in oil, could have 
been produced during the Lite of Chaucer, 
fince, according to the moft generally: re- 
ceived opinions, the art was not difcover- 
ed till nine years jubfequent to the poet’s 
death, by Johnab Eyck, ina fearch for 
varnifh. 
But Mr. Rafpe, in his Critical Effay on 
Oil-painting, publifhed in 1781, has 
proved its exiftence long before the pre- 
tended difcovery cf Van Eyck ; and even 
ci‘ed a German writer upon painting, of 
the ninth or tenth century, (whofe manu- 
{cript yet exifts in this country,) who 
mentions the ufe of coals for the purpofe 
of beating the oil-preparatwus. 
Governor Pownal, in the ninth volume . 
of the Archeologia, has produced, from 
the facrifty of Ely, fome accounts that are _ 
as explicit as poffisle, that oil was ufed in 
the mixture of colours both in the reign of 
Edward II, and Edward III. The firft 
fiys—** In tres lagenis et dimid. olet pra 
ymagnibus fuper columnas depingend.”-— 
The next, “ In 31 lagenis et dimid. olet 
pro color. temperand;” and the 
third, ‘ In oleo empt. pro picture facicnd. 
in capella.” Could oil-painting, fays 
Lord Orford, be more exactiy defcribed 
at this day ?—-r. Oil for painting images 
on columns.—2. Oil for mixing colours, 
(which is diftinguifhing it from varnifh.) 
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