METEOROLOGY, 
man who made these observations termed 
the elevations and depressions now describ- 
ed equatropical motions, and asserts, that 
they were regularly performed while the 
barometers were on the sea, but they were 
seldom observed on a river, or when the 
instruments were on shore. This circum- 
stance leads us to concur with Dr. Thomson, 
in supposing that the singular fact is to be 
ascribed to the motion of the ship, “ which 
by regularly agitating the mercury, might 
make its elevations and depressions more 
sensible and correct than when the baro- 
meter continues stationary.” The range 
of the barometer increases gradually as the 
latitude advances towards the poles, till in 
the end it amounts to two or three inches. 
The following table, composed by the writer 
just cited, will explain the gradual increase 
alluded to, which he compiled from the best 
authorities. 
LatUude 
Places 
K-ange of tlie baromelei 
Greatest 
Annual. 
0” 
0' 
Peru 
0 
20 
_ 
__ 
§2 
23 
Calcutta 
0 
77 
- 
— 
33 
55 
Cape Town 
- 
— 
0 
89 
40 
55 
Naples 
1 
00 
— 
51 
8 
Dover 
2 
47 
1 
80 
53 
13 
Middlewick 
3 
00 
1 
94 
53 
23 
Liverpool 
2 
89 
1 
96 
59 
56 
Peteisburgh 
5 
45 
2 
77 
The range of the barometer is consider- 
ably less in North America than in the 
corresponding latitudes of Europe, par- 
ticularly in Virginia, where it never ex- 
ceeds 1.1. The range is more considerable 
at the level of the sea than on mountains, 
and in the same degree of latitude it is in 
the inverse ratio of the height of the place 
above the level of the sea. 
M. Cotte composed a table which has 
been published in the Journal de Physique, 
from which it appears extremely probable 
tliat the barometer has an invariable ten- 
dency to rise between the morning and 
the evening, and that this impulse is most 
considerable from two in the afternoon till 
nine at night, when the greatest elevation 
is accomplished ; but the elevation at nine 
differs from that at two by four-twelfths, 
while that of two varies from the elevation 
of the morning only by one-twelfth, and 
that in particular climates the Neatest ele- 
vation is at two o’clock The observations 
of M. Cotte confirm those of Mr. Luke 
Howard, and fiarm them it is concluded 
that the barometer is influenced by some 
depressing cause at new and full moon, and 
that some other makes it rise at the 
quarters. This coincidence is most con- 
siderable in fair and calm weather; the 
depression in the interval between the 
quarters and conjunctions amounts to one- 
tenth of an inch, and the rise from the con- 
junctions to the quarters is to the same 
amount. 
The range of this instrument is found to 
be greater in winter than in summer ; for 
instance, the mean at York during the 
months from October to March inclusive, 
in the year 1774 was 1.4S!, and in the six 
summer months 1.016. 
The more serene and settled the weather 
is the liigher the barometer ranges, calm 
weather with a tendency to rain depresses 
it, high winds have a similar effect on it, 
and the greatest elevation occurs with 
easterly and northerly winds, but the south 
produces a directly contrary effect. Ac- 
cording to the Asiatic Researches it is al- 
ways observed to be highest with north 
and north-west winds, and the reverse when 
the south-east prevails ; it falls rapidly pre- 
vious to violent tempests, and is greatly 
agitated while they continue. It has been 
remarked by Mr. Copland in the Transac- 
tions of the Society of Manchester, that 
“ a high barometer is attended with a tem- 
perature above, and a low barometer with 
one below, the monthly mean.” Various 
but almost altogether unsuccessful attempts 
have been made to explain the phenomena 
we have enumerated ; that of Mr. Kirwan 
carries considerable plausibility, though it 
is not considered quite satisfactory. In order 
that his ideas on the subject may be clearly 
understood, we shall give what may be 
considered an abstract of his theory, im- 
proved by Dr. Thomson. The density of 
the atmosphere is evidently greatest at the 
poles, and least at the equator, as the cen- 
trifugal force at the latter, the distance 
from the centre of the earth, and the heat, 
all contributing to lessen the density of the 
air, are at their maximum, when, at the 
pole it is exactly the reverse. In every 
part of the world the mean height of the 
barometer placed at the level of the sea will 
be found to be 30 inches, consequently, the 
weight of the atmosphere is the same in all 
places ; its weight depending on its density 
and height; where the former is greatest 
the height must be the least, and where its 
density is least the height is the greatest. 
Arguing from these facts it will, therefore; 
appear that the height of the atmosphere 
