AMERICAN AGRICULTURIST. 
[August, 
Q3k 
est Danish settlement, lat. 72° 47', three hundred 
and seventy miles within the Arctic circle, Dr. 
Kane found at the Governor’s house, “ a little 
paling, white and garden-like, inclosing about 
ten feet of prepared soil covered with heavy glass 
frames; under which, in spite of the hoar-frost 
which gathered on them, we could detect a few 
bunches of crucifers, green radishes, and turnip 
tops. It was the garden, the distinctive append¬ 
age of the Governor’s residence..At last 
came the crowning act of hospitality, pale, 
yet blushing at their tips, and crowned each with 
its little verdant tuft, ten radishes ! Talk of the 
Mango of Luxon and of other luxuries of the trop¬ 
ics ; but the palate must cease to have memory 
before I yield a place to any of them alongside 
the ten radishes of Uppernavick.” 
But we can not pursue this subject. Enough 
has been said to remind us what a wonderful 
provision God has everywhere made for the 
welfare of his creatures ; that even amid polar 
snows, where we should naturally look only for 
barrenness and death, even there can be found 
life, and growth, and beauty. 
--- - ■ — -- 
The Barometer—Its Usefulness to Farm¬ 
ers and Others. 
Of the construction of the Barometer and its 
uses, very little is known by people generally. 
We propose here to give a few plain illustrations 
of the instrument which will help the unscientific 
reader to understand it. The word Barometer 
means weight-measurer (from baros, weight, and 
mctron, measure.) The barometer is used to meas¬ 
ure the weight or pressure of the air, and to in¬ 
dicate changes in the pressure. Storms, drouth, in¬ 
deed almost all changes in weather are preceded 
by changes in the pressure of the air ; hence the 
barometer is very useful to those who have crops 
to gather, and indeed to all classes whose busi¬ 
ness or pleasure makes it desirable to have some 
previous indication of the kind of weather that 
may be looked for. 
The air which surrounds the earth extends up¬ 
ward (or outward) from the surface for a great 
distance, constantly decreasing in density and 
weight as we ascend from the surface of the 
earth. At the level of the sea, 100 inches of air 
weigh about 31 grains. A cubic foot of air 
weighs about 536 grains; and about 13 cubic 
feet of air weigh a pound. (A box 2^ feet each 
way contains nearly a pound of air. A common 
barrel contains about one-third of a pound of air.) 
Though the air extends 40 to 50 miles upward, 
and probably much beyond this, in an extremely 
rarified state, yet were the whole atmosphere re¬ 
duced to a uniform density similar to that at the 
level of the sea, it would extend upward onl. 
26,100 feet, or about 5 miles. The entire weight 
of air on our globe is 11.624,914,885,408,838,323 
pounds, or more than eleven quintillion pounds ! 
This w’eight of air is equal to a layer of water 
over the entire surface of the earth nearly 34 
feet deep, (33.92 feet.) 
As the whole air is equivalent to 26,100 feet in 
bight of the air at the level of the sea, and as 
one foot of air weighs 536 grains, it follows 
that there is piled up upon every foot of the 
earth’s surface a column of 26,100 feet of air, 
weighing 26,100 times 536 grains, or full 2,000 
pounds. As there are 144 square inches in a 
foot, it follows that the weight of the air or down¬ 
ward pressure is nearly 15 pounds upon every 
square inch. Illustration. —Lay a board, one foot 
square, upon the end of a scale beam, and then 
withdraw the air from under it so that there 
hall be no upward pressure, and the air will 
press down the board with the force of a tun. 
The reason why we do not perceive this enor¬ 
mous pressure of air upon our bodies, and indeed 
upon every thing around us, is, that the air being 
a fluid, presses in all directions alike, so that 
while the air presses down upon any spot, at the 
rate of 15 pounds to the inch, the air around and 
under presses up just as much. Illustration .— 
Place a tun of iron or lead upon a board a foot 
square, and then remove the air from above the 
board, and the surrounding air will press under 
the board and lift it up with the tun of metal upon 
it. Take a teacup, bowl, or a quart cup, and fill 
it even full with water ; cover it with a piece of 
newspaper, fitting closely upon the rim ; then 
carefully invert it, and the water will not run 
out. The paper furnishes a smooth surface for 
the air to press up against the water. The same 
would be the case if the cup were 30 feet high, 
the upward pressure of the air being greater than 
the downward pressure of the 30 feet column of 
water. 
Fig. 1. 
Take a tube like fig. 1, say 40 feet long, and fill 
it with water. .Now turn it up to the position 
shown in fig 2, and the water will partly run out, 
but the surface of the water in the 
long arm, at a, will stand nearly 34 
feet (33.92) higher than in the short 
arm at b. The reason of this is, 
that there being no air left above a 
to press down, the column of air, 
26,100 feet above b, will just bal¬ 
ance or hold up the 34 feet column of 
water between a and b. Place one 
end of a pump log or pipe in water,and 
put into it a tight piston. Now 
draw up this piston so as to lift off ^ 
the pressure of the air inside, and 
the air upon the water on the out¬ 
side will press the water up into the Fig. 2. 
pipe nearly 34 ft. But if the piston 
is drawn above 34 feet, the water will not follow 
it further, because the pressure of 
the air is only equal to a column 
of water 34 feet high. On this 
account, we provide force pumps, 
instead of suction (air-lifting) 
pumps, for wells over 30 feet. 
If we take a tube of two arms 
like fig. 3, and into one arm, w, 
pour water, and into the other, 
m, pour mercury (quicksilver), we 
shall find the water standing 13) 
times higher than the mercury, 
because the latter is 13) times 
heavier than water. A column of 
water 34 feet, will balance a col¬ 
umn of mercury 2)- feet. 
The Mercukia., Barometer— If in fig. 2 we 
put mercury instead of water, the mercury will 
sink down so as to stand only about 30 inches high, 
because a column of air 26,100 feet high, is about 
as heavy as a column of mercury 30 inches high. 
Take a tube closed at one end, and say 33 inches 
long, and fill it with mercury. Then close the 
open end tightly with the finger, and place it in 
a cup of mercury, as shown in fig. 4. The mer¬ 
cury in the tube will ordinarily sink down to a 
point between 29 and 30 inches high. There is no 
air in the upper end of the tube to force the mer¬ 
cury down ; and the surrounding air presses upon 
the mercury in the cup, and balances the column 
30 inches high. It is precisely the same as if 
31 
20 
23 
this colamn of 30 inches of mercury were staftd- 
ing upon one end of a scale beam, and a column of 
air of the same size, but 26,100 feet high on the 
other end of the beam—they balance 
each other. This cut (fig. 4) shows 
the simplest form of the barometer. 
The numerals upon the side of the 
tube indicate the hight of the column 
of mercury above the surface of the 
mercury in the cup, and consequent¬ 
ly show the amount of the weight 
or pressure of the air which balances 
or supports this column of mercury. 
There are many forms of the mercu¬ 
rial barometer, but they are all made 
essentially on the same principle. 
In one kind, the tube is enclosed in 
a wooden frame, with a glass face. 
In another, the end of the tube is bent 
upward, as in fig. 2. In another, a 
leather bag holds the mercury at the 
bottom, instead of the cup, which 
makes the instrument more port¬ 
able. Too much space would be re¬ 
quired for a description of these va¬ 
rious modifications ; and our main 
object is only to illustrate the prin¬ 
ciple of the barometer, and to speak 
of some of its uses. 
Fig. 4. 
Variations of the Barometer. —As the hight ol 
the column of mercury depends upon the column 
of air pressing it up, it will readily be seen, that 
should we carry the barometer above the level 
of the sea, there would be less air above to press 
upon the mercury, and of course it would not rise 
so high. Thus: if a column of air 26,100 feet 
high supports a column of mercury 30 inches 
high, it will easily be seen that if we carry the 
barometer up one-thirtieth of the hight of the air 
(or 870 feet), there would only be twenty nine- 
thirtieths of the air left to press u-p the column of 
mercury, and it would stand only 29 inches high. 
Illustration .—One of the early experiments in the 
discovery of the barometer, was that o*f Perrier. 
He filled two tubes, and found that at the foot of 
a mountain, the column of mercury in each tube 
stood 28 inches high. On taking one of the tubes 
to the top of the mountain, which was nearly 3,200 
feet higher, he found the column of mercury only 
24-f inches high. The column fell as he ascend¬ 
ed the mountain, and rose as he descended. 
It is easy to perceive, therefore, that a barom¬ 
eter is a most useful instrument for determining 
the hight of mountains and high land. (The air 
is more and more rarified as we ascend, so that 
considerable allowance must be made for this. 
So also we must take into account the tempera¬ 
ture, moisture, etc. Accurate formulas are made 
for all these variations, so that it is now perfectly 
easy to know the hight of any locality by observ 
ing the hight of the column of mercury in the 
barometer, and applying the corrections for tem¬ 
perature, etc.) With some of our readers who 
live nearly on the level of the sea, the mercury 
will range a little below 30 inches, during most 
of the year, while with others who live on ele¬ 
vated land, it will stand at 28, 27, 26, or per¬ 
haps as low as 25 or 24 inches in some cases. 
The Barometer as a Weather Guide .—If the air 
always remained at rest, and equally dry and 
warm, the pressure would be uniform, and the 
column of mercury would remain at the same 
hight, in all localities at the same elevation above 
the sea level. The greatest cause of varia¬ 
tion, however, is the change in pressure produced 
by winds. If a current of wind set towards a 
particular point, of course, the air will be com- 
