Eastern times. [volume] (Bath, Me.) 1846-1857, 1852-07-29
The Formation of Dew,

The Formation of Dew.
In surveying any part of nature, the philo-
sophie mind discovers much that is amusing
and interesting. Whether the research be |
confined TO an investigation of the ear,h--of
the mountains and hlls-plains and valleys
rocks and sands-rivers and oceans--,hat d.
versify its figure, or whether we examine the
beauties, curiosities and wonders, and ever va
rying scenery that adorn lis surface, we are at
every step Of our discovery, forcibly struck
with the beauties of nature and the valuable
lessons which they teach. And in many in
stances we are too apt TO overlook what would
well pay US for investigating. because ii is so
commonplace and simple Hence, by so DO
ing, we curtail our means of knowledge, and
consequently one of the most fertile sources of
happiness. For 10 those who are in the habit
ual practice of studying the operations and
workings of nature--ihe springhg grass, the
waving grain, the gigantic trees OF the forest,
spreading far around their shelterihg branches,
benealh whose shade the schoul boy is wont to
spend the hours of his pastime, and even the
still falling dew, afford matter that will pay
them richly for investigation, and open TO their
minds high source OF happiness.
Knowing with what delight the younger
members of the family search your instructive
and interesting columns, it is hoped few re-
marks upon the last named. the falling dew,
r,,,, ~, rroya a,,irol,,
The formation of moisture upon the outside
of pitcher containing ice water, or other water
sufficiently cold has not escaped the notice of
the most unobserving. Even the sons of the
backwoodsmen have observed it, and not con-
tent with the mere observation, they have en-
quired for the cause, and those who would
blush TO have persons think they were ignorant
of SO simple thing, have answered these qnes-
tions by saying 1t is caused by the pitchers
sweating > this, these urchins carefully store
up within their memories, TO reason upon at
their leisure. After much reasoning and talk
upon the subject, and reviewal of all they
have heard about cold water sweats, they final
ly come TO the conclusion that if water possess
ess the power of causing SO hard and impene-
trable substance as pitcher to sweat SO pro-
fusely, its effects upon the human system have
never been overrated and its value in produce
ing perspiration beyond calculation That
cold water sweats when judiciously applied,
are very beneficial 10 human beings, there is
probably no doubt; but TO suppose that pitch
er 'sweats,' on the same principle, would be as
absurd as i. is laughable.
To understand what does cause it to sweat,
we have only to remember thai the atmosphere
always contains some portion of waterY vapor,
and it will be observed that if the water in the
pitcher is warm, no moisture will be deposit
ed on its surface. And We can ascertain the
dew point, by dropping ice into the pitcher
AS soon as sufficiently cold, the water is seen
to commence collecting. The cause, we then
see, is the vapor of the air coming in contact
with body so much colder than itself, that it
is condensed And now, keeping this in mind
we shall be prepared to understand how dew is
formed. The earth, during the day, is con-
stantly receiving heat from the sun. After
the sun has set, and the atmosphere becomes
colder than the earth, the earth commences
giving off its heat, and it continues TO pass off,
until the earth becomes so cold, that the vapor
of the atmosphere is condensed as it comes in
contact with it. 1t will also be noticed, that
on some cloudy nights there is no dew. To
I - ~ 1a, fxhe he
manner in which the earth is cooled down.
We have said that when the atmosphere be-
comes colder than the earth, the earth COM
mences giving of its heat. Now on clear
night the heat passes up high, it being well
known that heated air always rises; but 1t
there are clouds short distance from The earth
the heat Oh reaching them, is reflected back to
the earth. and thus the process continues, the
earth receiving nearly as much heat as it gave
j. off; consequently the earth and atmosphere
being nearly of the same temperature, no dew
is deposited and the nearer their approach TO
the same temperature, the less dew there is
and other things being equal, the greater the
difference the moro dew; therefore we see
the reason of some bodies being dripping
with moisture, while others are nearly dry.
Green substances as grass and such bodies
as iron, being better conductors Of heat, than
such bodies as boards, dust Of the streets, are
those upon which we find but little dow
Portland Transcript.