11(3 
AMERICAN AGRICULTURIST. 
[March. 
HOTS <k (B0WMTO 
The Doctor’s Talks. 
One of my young friends writes: “I saw it 
stated that at the observatory on top of the White 
Mountains the wind was blowing at the rate of 50 
miles an hour. Did they guess at it, or have they 
some way of measuring the wind ? By the way can 
you not tell us something about the wind and why 
it blows?”—Perhaps my correspondent did not 
think of it, but his question is a timely one, as the 
“ Talk ” comes in the most blustering of all months 
— March, which is quite sure to furnish abundant 
illustrations of the wind and its doings. To tell 
you something about wind, we must first ask 
Wliat is Wind? 
The books give a brief but sufficient answer when 
they say, it is “air in motion.” You will then be 
quite sure to ask: “ What sets the air in motion ?” 
The answer to this must 
be, “the heat of the 
sun.” Before we talk 
about the air in motion, 
we must make sure if 
we know a few facts 
about air. I suppose it 
is not necessary to prove 
to those young people 
who are old enough to 
read this, that the air, 
while we can not see it, 
is a real substance, as 
much as a board or a rock. 
If you tie securely the 
neck of a partly blown- 
up bladder, or an India- 
rubber foot-ball, you can not possibly, by pressing 
it with your hands, bring the sides of the bladder 
or ball together. Even if you stand upon it, it will 
hold your weight. This readily shows that air is a 
substance ; you can have another proof by rapidly 
moving a common fan or even a shingle. If you 
move either of these back and forth edge-wise, and 
then flat-wise, you will find a great difference in the 
ease of doing so. When you move the flat surface 
against the air, as in fanning, you find a resistance ; 
there is something, though you can not see what, 
that prevents a rapid motion in this direction, 
a real substance. Like most other substances, 
Air Expands wlieu Heated, 
that is, it takes up more space than it did before. 
If you place the partly filled ball or bladder near 
the fire, the air within will be heated, and will ex¬ 
pand until it quite fills out the thing that holds it. 
Warm air being lighter than cold air, rises. You 
know that in au open fire-place, the warm air is 
passing up the chimney and carrying the smoke. 
Tissue paper balloons are filled with hot air, and 
this being much lighter than cold air, rises, aud 
takes up the balloon. That warm air is always ris¬ 
ing from a heated surface may be shown by one of 
those toys that boys often make. A circle of paper 
is cut in a spiral form, and placed on a wire as in 
figure 1. This when placed on the stove will re¬ 
volve very rapidly, though the upward motion of 
the air is so slight that it cannot be felt. In a room 
where there is a fire in a stove, or where even 
a lamp is burning, there is always a disturbance. 
The Air is Constantly in Motion. 
It rises, when heated by the stove, and there is 
also another motion, coldei; air rushes towards the 
stove to take its place, as shown in figure 2, where 
the arrows show the rising of the heated air, and 
the rushing in of cooler air from all sides. These 
movements of the air, caused in the room by the 
heated stote, by a lighted lamp, or other source of 
heat, so gentle that we do not feel them—currents, 
we call them, are governed by the same laws as 
The More Rapid Jlovements We Call Wind. 
Where air is unequally heated there is motion. 
Franklin was a great philosopher for his day, and 
illustrated very important facts by the most simple 
experiments. He showed that lightning was the 
same as electricity, by means of a boy’s kite and a 
key, and to show that when two bodies or quantities 
of air were unequally heated there would be currents 
between the two, he used simply a candle. You 
can readily try Fraukliu’s experiment. Open the 
door a little between a room in which there is a 
fire, and one where there is no fire, and the air is 
colder—just a crack will answer. If you hold a cau¬ 
dle at the top of the door, the flame will at once be 
bent and point towards the cold room ; if you hold 
the candle near the floor, the flame 'will point in 
the opposite direction, showing that there is a cur- 
Fig. 3.—AN ANEMOMETER OR WIND MEASURER. 
rent of warm air going out above, and another 
current of colder air coming into the room below. 
“ What has this to do with the Wind ?” 
you may ask. It shows in a small way what is 
taking place on the surface of the earth. The stove 
heats the air of the room, and there is a disturb¬ 
ance, the air is set in motion, and its currents are 
passing in various directions. When a portion of 
the earth is heated by the sun, that heats the air, 
which rises, and air from cooler parts comes rush¬ 
ing in to take its place—this air comes with greater 
or less force, and when we can feel it moving, we 
call it wind. You know that the part of the earth 
near the equator is the hottest, the heat of the sun 
falls more directly there than elsewhere. The. 
heated air rises, and air from both the north and 
the south comes in, and we might expect that there 
would be a coustant wind blowing towards the 
equator from both directions. But there is some¬ 
thing else to be considered ; the earth is rapidly re¬ 
volving, aud this changes the direction of these 
wiuds, which in some parts of the ocean blow so 
contantly from the north-east and south-east that 
they are called “trade winds.” There are other 
winds besides these ; wherever there are deserts, 
or wide plains, these become heated and cause 
local winds. The islands in the hot portions of the 
globe have a sea-breeze in the day and a land breeze 
at night. When the island becomes heated, the 
air above it rises, and this starts a current towards 
the island from the sea. As night comes on the 
island soon cools, and when it becomes cooler than 
the sea, the wind blows away from the land. Winds 
are much affected by lakes, mountains, etc., but 
their origin may be traced to the sun, which heats 
the earth’s surface unequally. There is a great 
difference in the force of the wind : sometimes so 
gerrtle that it barely moves a leaf, again so strong 
that we can barely make our way against it, up 
to the violent tornado which sometimes unroofs 
and destroys buildings, uproots trees, and often 
carries men and animals along in its course. The 
rate at which the wind travels is measured by an 
Anemometer, or Wind Measurer. 
The name looks hard to remember. You are 
familiar with the last half of it in thermo-meter, 
and baro-meter, and probably know that meter 
means a measure. If you will recollect that anemos 
is the Greek word for wind, I think you will have 
no trouble with Anemo-meter. There are different 
kinds of these instruments, but the one most in 
use is shown in figure 3. It consists cf four brass 
cups arranged upon arms ; these are readily turned 
by the slightest wind, and they move a wheel work 
which shows how many revolutions the cups make 
in a given time, and consequently how fast the 
wind is moving. A gentle breeze moves four aud 
five miles an hour, a brisk wind 20 to 25 miles, and 
a violent hurricane from 80 to 100 miles an hour. 
Another Boy—Bfiis Sad iPate. 
In the December American Agriculturist we gave 
some account of “ Those Two Boys,” who came to 
our office after a hard experience, and who were 
fortunately restored to their parents. Last autumn 
another boy of 16, who had got similar sea-going 
notions into his head from reading the high-colored 
false stories about life at sea and on ship-board, 
stole away from home in the same manner. Un¬ 
fortunately he fouud a sailing craft just wanting a 
boy, and he was taken in. The vessel went up to 
a Maine port, and on Jan. 1, sailed southward. 
When off Cape Ann, Mass., the vessel was struck 
by a gale and disabled. The men and boys sprang 
into a boat, and for three days aud nights they were 
without food or water, wet with rain and sleet, aud 
chilled with cold. When picked up by a chance 
vessel, two men and our wayward boy were lying 
in the boat pale in death, and frozen to rigidity. 
The poor boy delirious with hunger, thirst and cold, 
had kept asking, “ wheu shall we get to land ? ” 
One of the men stripped off his own coat and 
muffled him in it, but it was of no use. He 
talked of his parents to the last, sent a fond 
message to them, and the sleep of death came on. 
How many similar cases have there been, on the 
196 steamships, aud the many hundreds of sailing 
vessels that have succumbed to the ocean’s fury 
during the single year past. Pity indeed, that the 
watery graves of these deceived and deluded boys, 
led to flee from home and friends, could not have 
been filled by those men who, for the money re¬ 
ceived, write and publish story books and papers 
for boys filled with the enchanting falsehoods that 
carry away the imagination of young lads who 
would otherwise grow up as good men and useful 
citizens. Boys, don’t believe these stories—don’t 
read them—they are sugar-coated poison. 
The Death of Aunt Sue. 
The announcement in the daily papers that Mrs. 
Susanna Newbould died at h'er residence in Brook¬ 
lyn on Jan. 9th, was read with painful surprise. 
The last of her frequent notes to us had been as 
bright and cheery as ever; there was nothing in it 
to show that Aunt Sue was even ill, aud the 
news of her death came to us as suddenly as it will 
to you. Aunt Sue has so long provided our young 
readers with pleasing amusements that they have 
looked upon her as a friend. Many of you who 
have written her, know how kind were her replies 
to your questions, and liow even the briefest note 
seemed to be overflowing with good feeling. One 
must have been personally acquainted with her to 
know how bright aud witty, and at the same time 
how loving aud lovable she was. Besides being a 
talented writer, she was a skilled musician and 
composer of music, and an accomplished artist. 
Some of her notes show her wonderful readiness at 
illustration; where a picture would express her 
idea better than words, a rapid, often highly amus¬ 
ing sketch would tell the 6tory. But with all her 
!H 
Fig. L— nOT-AtR TOT. 
