METEOROLOGY. 
tJie wind at the rate of 70 miles an hour, 
while a perfect calm existed in tlie city and 
neighbourhood. 
There are many circumstances attending 
the operations of the air, which we term 
wind, that serve for a basis for well-founded 
conjectures, and those united to the result 
of daily observation, render the explanation 
of its phenomena tolerably satisfactory. It 
must be clear to the most common capacity, 
that as the rays of the sun descend perpen- 
dicularly on the surface of the eartli under 
the torrid zone, that part of it must, receive 
a greater portion of heat than those where 
they fall obli((uely ; the heat thus acquired 
communicates to the air, which it rarities 
and causes to ascend, and the vacuum oc- 
casioned by this operation is immediately 
fdled by the chill air from the north and 
south. Tlie diurnal motion of the earth 
gradually lessens to the poles from the 
equator : at that point it moves at the rate 
of fifteen geographical miles in a minute : 
this motion is coinraunicated to the atmos- 
phere in the same degree ; therefore if part 
of it was conveyed instantaneously from la- 
titude 30" it would not directly acquire the 
velocity of that at the equator; conseqently 
the ridges of the earth must meet it, and 
give it the appearance of an east wind ; 
the effect is similar upon the cold air pro- 
ceeding from the north and south, and this 
similarity must be admitted to extend to 
each place particularly heated by the beams 
of the sun, 
The moon being a large body, situated 
comparatively near the earth, is known to 
affect the atmosphere in its revolutions by 
the pressure of that upon the sea, so as to 
cause the flux and reflux of it, which we 
term tides, it cannot, therefore, be doubted 
that some of the winds we experience are 
caused by her motion. 
The regular motion of the atmosphere, 
known by the name of land and sea-breezes, 
may be accounted for upon the above prin- 
ciple : the heated rarifled land air rises, and 
its place is supplied by the chill damp air 
from the surface of the sea ; that from the 
hills in the neighbourhood becoming cold 
and dense in the course of the night, descend 
and press upon the comparatively jighter 
air over the sea, and hence the land breeze. 
Granting that the attraction of the moon, 
gnd the diurnal movement of the sun, affects 
our atmosphere, there cannot bea doubt but 
a w’estward motion of the air must prevail 
within the boundaries of the trade winds, 
{he consequence of which is an easterly 
current on each side : from this then it pro- 
ceeds that south-west winds are so fre- 
quent in the western parts of Europe, and 
over the Atlantic ocean. Mr. Kirwan at- 
tributes our constant south-west winds, par- 
ticularly during winter, to an opposite cur- 
rent prevailing between tlie coast of Mala- 
bar aud the Moluccas at the same period ; 
this, he adds, must be supplied from regions 
close to the pole, “ which must be recruited 
in its turn from the countries to the south 
of it in the western parts of our hemis- 
phere.” 
The variable winds cannot be so readily 
accounted for, yet it is evident that, though 
they seem the effect of capricious causes, 
they depend upon a regular system, arrang- 
ed by the great author of nature. That acr 
curate and successful observer of part of 
his works, the celebrated Franklin, disco- 
vered in 1740 that winds originate at the 
precise point towards which they blow. 
This philosopher had hoped to observe an 
eclipse of the moon at Philadelphia, but w as 
prevented by a north east storm, that com- 
menced at seven in the evening. This he 
afterwards found did not occur at Boston 
till eleven ; and upon enquiry he had reason 
to suppose it passed to the north-east at the 
rate of about 100 miles an hour. The man- 
ner in which he accounts for this retrogade 
proceeding is so satisfactory, that we shall 
give it in his own words, particularly as his 
assertions are supported by recent observa- 
tions both in America and Scotland. He 
argued thus : “ I suppose a long canal of 
water, stopped at the end by a gate. The 
water is at rest till the gate is opened ; tiien 
it begins to move out through the ^ate> and 
the water next the gate is first in motion, 
and moves on towards the gate ; and so on 
successively, till the water at the head of 
the canal is in motion, which it is last of all. 
In this case all the water moves indeed to- 
wards the gate; but the successive times of 
beginning the motion are in the contrary 
way, j:iz. from the gate back to the head of 
the canal. Thus, to produce a north east 
storm, I suppose some great rarefaction of 
the air in or near the Gulph of Mexico ; the 
air rising thence has its place supplied by 
the next more northern, cooler, and there- 
fore denser and heavier air; a successive 
current is formed, to which our coast aud 
inland mountains give a north-east direc- 
tion.” According to tlie observations made 
by Captain Cook, the north-east winds pre- 
vail in the Northern Pacific Ocean during 
the same spring months they do with u?, 
