1881.] 
AMERICAN AGRICULTURIST. 
7 
Explaining the Barometer and its Uses. 
The Greek word metron means a measure. 
Another Greek word, baros, means weight or 
pressure. Putting these two words together 
we have baros-metron, or our English word 
barometer, which means a measure of weight 
or pressure. The use of this word is limited 
to instruments for measuring the weight or 
pressure of the air.* Air would seem to have 
almost no weight, but 
the air in an ordinary 
barrel actually weighs 
- 8 3 /4 ounces ; or 2°/ 8 bar- 
Fig. 1. 
Fig. 2 . 
1 
rels of air weigh one pound. The air in a 
room only 10 feet square and 10 feet high 
weighs over 76 pounds. The weight of all 
the air on the surface of the earth is so great 
that it presses down upon eveiy square inch 
nearly 15 pounds (14.61), and upon every 
square foot 2,104 pounds, or over a ton! 
If we sink a deep tumbler in the water, 
and when full lift it nearly out, fig. 1 , with 
the mouth downward, the pressure of the 
air upon the water in the dish will keep the 
water up in the tumbler. If the tumbler 
were 84 feet long, the ail’ would still push 
the water up on the inside nearly to the top, 
but it will not push it any further up, how¬ 
ever high the tumbler may be, because 
the whole weight of the ah is equal to the 
weight of only about 33'/ a feet of water. 
If we put mercury (quicksilver) in the dish 
instead of water, the same effect will 
take place, but the mercury will rise 
only about one-fourteenth as high, 
because it is about 14 times heavier 
than water. Take a glass tube, (a, 
fig. 2 ,) 38 inches long, closed at one 
end, fill it with mercury and put the 
finger over the top end. Now tuna it 
down into a dish of mercury, b, and 
the mercury in the tube will sink 
down to c, leaving a vacuum above 
it. If the tube is an inch square on 
the inside, we will find that about 30 
inches deep will weigh nearly 15 
pounds. That is, the whole weight of 
air pressing on one inch is about 15 
pounds. Our glass tube of mercury, 
is a baros-metron, or as we English it, 
a barometer, a measurer of the weight 
or pressure of the air. We can set the 
lower open end of the tube in a box or 
bag of mercuiy, and the effect will be 
the same, for the air will press upon 
the bag and push the mercuiy up 
about 30 inches high in the tube. 
There are a good many foi’ms of 
barometers. A common one is shown 
in fig. 3, which is arranged to be car¬ 
ried about, and the top part is marked 
^ 3 off with fine lines, say a tenth of an 
' inch apart, so that we can see and 
note when the mercury goes higher or lower, 
as it will do if the pressure of the air is 
*The Greek word thermos means heat or warmth. So a 
ihermos-metron, or thermometer, means a measurer of heat. 
greater or less. This one has a thermometer at 
the left of the top to show the temperature also. 
Some Uses of the Barometer. 
If we go up on a hill or mountain, there is 
less air above to press upon the mercury, and 
it will sink down in the tube, say about one 
inch for eveiy 650 feet we go up. Then at 
one mile high (5,280 feet), the mercuiy would 
sink some eight inches, and show only about 
22 inches high in the tube. In this way, 
with good barometers and with proper al¬ 
lowances for heat, etc., they actually measure 
the hight of mountains very accurately. 
But the greatest use of the barometer is to 
foretell changes in the weather. If from 
any cause the air is lighter, or has less pressure 
in any place, the air from other places will 
flow in there, producing a wind. So if the 
mercuiy falls we may usually expect the 
ail- from elsewhere to come rushing in. If 
the seaman sees the mercuiy in his barom¬ 
eter fall very rapidly, he hurridly takes his 
sails in and gets ready for a strong wind, or 
hurricane, perhaps. But on land we gener¬ 
ally expect that if a wind from one place 
meets the air in or from another place which is 
warmer or colder, it will produce precipitation 
of moisture in the form of rain. There are 
several rules for judging by the movement of 
the mercury up or down when there is likely 
to be wind or rain, or both, and this can be 
done several hours in advance. So we see 
how a barometer can be very useful to farm¬ 
ers, and indeed to almost everybody. The 
rules for judging or predicting usually go 
with barometers, and we omit them here. 
The Weather Bureau at Washington, hav¬ 
ing telegraph lines to all parts of the country, 
can learn where the barometer is high, and 
where low, and thus tell where the air will be 
likely to move as wind ; and by knowing the 
temperature, etc., the kind of weather, the 
movement of storms, their rapidity, the time 
of their approach, etc., can be foretold with a 
great deal of accuracy. Every farmer may 
well have a barometer and learn to judge 
from it for his own locality. A very good 
barometer was described in the last Sep¬ 
tember American Agriculturist, on page 383. 
Conversion of Wagons into Sleds. 
A few years ago a member of our family 
was caught “ on wheels ” about sixty miles 
from home, a fall of a foot 
of snow making it impos¬ 
sible for him to return with 
a wagon. Being handy 
with tools, and where oak 
planks were to be had, he 
made a sled in a day, put 
his wagon upon it, and 
F'S-came home in good shape. 
In this case the sled was simply two 
runners cut from the plank, long enough to 
hold the wagon-body, and fastened together 
by plank cross-pieces securely nailed to the 
runners. The wheels were removed and 
the body lashed to the runners by ropes. 
Four independent runners may be quickly 
made, one to go in place of each wheel. Each 
runner is of three pieces of board, two form¬ 
ing the sides, and the other the top. Figure 1 
is a cross-section, showing the position of the 
side-pieces and the axle of the wagon. The 
outer side-piece is sawed full of kerfs at the 
front end that it may bend around and meet 
the other side-piece. The inner side of this 
piece is shown in figure 2. Cleats to give 
strength are put on the side. The runner is 
shown complete in figure 3. A spring wagon 
thus arranged with runners make a quite 
passable sled. This contrivance is not for 
general use, but only for an emergency. 
Another method occasionally found con¬ 
venient, is shown in figure 4. Two stout 
Fig. 3. —THE RUNNER FINISHRD. 
hickory saplings are smoothed on two sides 
and grooves made for the wheels to stand in. 
The runners thus made are fastened to the 
wheels by stout wires which pass through 
holes bored in the runners—the front ends 
being bent upwards and fastened to the fel¬ 
loes in the same way as the bottom part. 
A Harrow and Smoother Combined. 
Mr. “C. H. S.,” Miami Co., O., sendsasketch 
of an appliance which he thoroughly tested 
while preparing his wheat ground. It is a 
combination harrow which answers two 
purposes, viz.: “First, crushing the clods; 
and second, securing a smooth surface by 
covering the harrow marks in advance of the 
drill, so that the seeds may reach a uniform 
depth. The poles should be the same length 
in feet as the harrow is in width ; diameter to 
suit the soil. Two holes, large enough to ad- 
A HARROW WITH SMOOTHING LOGS. 
mit the chains, should be bored about one 
foot from each end of the poles—the poles be¬ 
ing keyed apart the same distance with small 
wedges of wood to keep from clogging.’' 
