Herald of the times. [volume] (Newport, R.I.) 1830-1846, 1839-06-27
From the n. Y. Evening Post OF the 10Th inst
MIR. EsPY's THEORY OF STORMS.

Professor Espy delivered on Saturday
evening at Clifton Hall, the first OF his lee
tures on The causes and formation Of clouds
and storms. Abont two hundred persons
were present, who listened with much at
tention and interest. lie commenced his
lecture by stating the principles from which
his theory ofmeteorology is deduced. These,
he observed, were already well known to
men of science, though their consequences
had not hitherto been traced out. lie
showed that by cooling the atmosphere, at
the surface OF The earth, down to certain
degree OF temperature. fog or visible vapor.
or what IN higher region OF the atmosphere
is called cloud, is always produced. This
degree OF temperature Is called by phioso-
piers The dew point, and is higher or lower
according to the quantity of moisture con
tanned IN the atmosphere. II The atmosphere
be highly charged with moisture, a slight
reduction Of the temperature will effect the
change; If it be unusually dry, it must be
cooled considerably more. Professor ESpv
then stated the law of temperature at diff.
ferent heights ofthc aimo sphere. AT hun
dred yards above the surface of the earth,
the air is found 10 be very little more than
one degree Of Farenhet's thermometer col
der than at the surface, at two hundred yards
a little more than two degrees colder and so
on, one degree for every hundred yards that
you rise in the atmosphere. The air which
Is raried and mnde lighter by the heat of the
sun ut the surface Of the earth, therefore, is
cooled down to the dew point so soon as il
rises 10 the proper height from the ground,
and cloud is produced BIT there is another
cause which operates Ia reduce the tcmpcra-
ture of rariied air as il mounts to the higher |
regions Of the atmosphere. Air suddenly
expanded, always becomes cooler II by |
means OF an air pump, you exhaust a receiver
Of half the air il contains. the remainder will
Immediately expand so as TO fill the receiver,
and at the same time become ninety degrees
colder. Apply this principle to column of
warm air ascending in the atmosphere. As
II rises, 1t becomes relieved of portion Of
the atmospheric pressure which it sustained
at the surface, and consequently expands into
larger space, aud becomes proportionably
reduced in temperature.
From these laws Mr.. Espy proceeded 10
d'duce his theory of clouds and storms, which
he did, so far as he proceeded on Saturday
evening, with much ingenuity and clearness.
lie showed by neat experiment the forna.
ton Oft cloud in glass tube, by The mere
expansion Of Atmospheric ar. lie gave
briefly the elements of calculation by which .
the height Of the base Of a cumnlose cloud !
from the surface Of the earth may be at any |
time ascertaned by thermometer and n /
tumbler of water. lie gave beautiful ,hco.
ry Of hail storms, showing them to be produ |
ced by ascending columns Of rariicd air,
which"exrand prodiglously as they rise in
the atmosphere and throw off the hail on
each side, from the edges Of the cloud aud not
from it's centre. 1t is owing TO this cause
that hail storms fall; as is observed to be the
case, in tracts with Intervals between them.
Concerning the relation of winds TO storms,
MIR. E,py observed, that 1t has been fully as.
certained that they blow from all sides to-
wards the tract Of country where the storm
is generated, while in that tract there is near !
ly or almost a calm lie gave several ex-
ample OF storms extending over very con.
siderable tract Of country, in regard to which
il had been fully ascertained that The winds
blew towards them from every quarter Of
the surrounding region where the storm was
not felt.