182 L O R D A N S O N ’ S V O Y A G E
derably hotter than what was at any time felt by a (hip of Mr. An-
. Jon's fquadron, in running from hence to Cape Horn and back again,
and paffing twice under the fun; for, in the fummer of that year,
the thermometer'in London (being one of thofe graduated accordin
g to themcxho&oiFahreriheii) flood once at 78°; and thegreateft
height at which a thermometer of the fame kind flood, in the
'foregoing'Ihip, I find to be 76°: this was at Si. Catherine's, in the
'latter end of December, when the fun was within about three degrees
o f the vertex. And as to Peterjburg, I find, by the a61s of
the academy eftablifhed there, that, in the year 1734, on the 20th
and 25 th o f July, the thermometer rofe to 98° in the fhade; that
is, it was twenty-two divifions higher than it was found to be at
St. Catherine's; which is a degree of heat, that, were it not autho-
rifed by the regularity and circumfpection with which the obferva-
tions feem to have been made, would appear altogether incredible.
I f it fhould be afked, how it comes to pafs then, that the heat
in many places between the tropics is efteemed fo violent and in-
fufferable, when it appears by thefe inftances, that it is fometimes
rivalled or exceeded in very high latitudes not far from the polar
circle? Iftiall anfwer, that the eftimation o f heat, in any particular
.place, ought notto be founded upon that degree of heat which
may now and then obtain there ; but is rather to be reduced from
the medium obferved in a whole feafon, or perhaps in a whole year:
.and in'this light it will eafily appear, how much more intenfe the
fame degree of heat may prove, by bring long continued, without
remarkable variation. For inftance, in comparing together St. Catherine’s
and Peterjburg, we will fuppofe the fummer-heat at
St. Catherine's to be 76°, and the winter-heat to be twenty divifions
Ihort o f i t : I do not make ufe of this laft conjedlure upon fuffi-
cient obfervation ; but I am apt to fufpefi:, that the allowance is
full large. Upon this fuppofition, then, the medium heat all the
year round will be 66°,' and this perhaps by night as well as day,
with no great variation : now thofe who have attended to thermometers
will readily own, that a continuation of this degree of heat
for
R O U N D T H E W O R L D . 183
fora length of time, would, by the generality o f mankind, be fly led
violent and fuffocating. But Peterjburg, though, a few times in
the year, the heat, by the thermometer, may be confiderably greater
than at Si. Catherine’s, yet, at other times, the cold is immenfely
Iharper, the medium for a year, or even for one feafon only, would
be far Ihort of 60°. For I find, that the variation of the thermometer
at Peterjburg is at leaft five times greater, from its higheft
to its loweft point, than what I have fuppofed to take place at
St. Catherines.
Befides this eftimation of the heat o f a place,, by taking the medium,
for a conliderable time together, there is. another circum-
ftance, which will ftill augment the apparent heat.of the warmer
climates, and diminifti that of the colder, .though I do not remember
to have feen it . remarked in any author. T o explain myfelf
more diftin&ly upon this head, I muft ohferve, that the meafure o f
abfolute, heat, marked by the thermometer, is not the certain criterion
of the fenfation o f heat with which human bodies are affected
; .for as the prefence and perpetual fucceflion of frelh air is
neceflaty to our refpiration,..fo there is a fpecies of tainted or ftag-
nated air often .produced by the continuancemf great heats, which,
being lefs proper for refpiration, never fails to-excite inus.an idea,
of fultrinefs and fuffocating warmth, .much beyond .what the heat
of. the air alone, „fuppofing it pure and agitated, would occafion.
Hence it follows, .that the mere infpeftionof the thermometer w ill
never determine-the heat which: the human body feels from, this
caufe; and hence it follows too, that the heat in mofl places between
the tropics, muft be much more troublefome.andunealy, than,
the fame degree o f abfolute heat in a high latitude: for the equability
and duration of. the tropical heat contribute to impregnate,
the air with a multitude of fleams and.vapours from .the foil and
water; and thefe being, many of them,- of an impure and noxious
kind, and being not eafily removed, by.reafon of the regularity o f
the winds in thofe parts, which only (hift the exhalationsfrom place
to place, .without difperfing them, the atmofphere is by this means'
rendered