можете мне текст перевести MEASURING ATMOSPHERIC PRESSUREThe air surrounding the earth

Сможете мне текст перевести
MEASURING ATMOSPHERIC PRESSURE
The air surrounding the earth is really a mixture of well-known
gases: about 77% nitrogen, 21% oxygen, and 1% argon. The remaining
1% includes small quantities of such gases as carbon dioxide, hydrogen,
neon, krypton, helium, ozone, and xenon. The atmosphere is
the most dense at sea level. For measuring the atmospheric pressure
a device, called a barometer, is used. There are in common use today
two kinds of barometers the mercury barometer and the aneroid
barometer.
The mercury barometer was invented by the Italian physicist, Evangelista
Torricelli, some 300 years ago. Torricellis experiment is illustrated
in Fig. 4. A long glass tube is filled with mercury and the
finger placed over one end as shown in the diagram. This tube is then
inverted with the open end in a dish of mercury and the finger is removed
as in the diagram. At the instant the finger is removed, the mercury
level drops in the tube to a height h as shown. The mercury drops until
the pressure due to its own weight inside the tube is equal to the atmospheric
pressure outside. At sea level
the height at which the mercury
column stands is about 30 in.
This height will be the same regardless
of the diameter of the
tube or the length of the vacuum
space at the top. It was the
French philosopher and mathematician,
Blaise Pascal, who
first showed that when a mercury
barometer is taken to the top
of a mountain, the height of the
mercury column drops considerably.
It drops because there is
less air above that point and
hence a lesser downward pressure
on the free mercury surface.
Standard atmospheric pressure is
defined as the pressure equivalent
to a column of mereury 76 cm
high when the temperature is
О С. (This is equivalent to 29.92 in. of mercury at 32 F.) Standard atmospheric
pressure is equivalent to 14.7 lb/in2.
Some barometers work on a different principle from the mercury
weather glass. They are known as aneroid barometers. An aneroid
barometer consists of a thin metal box from which the air has been removed.
The atmospheric pressure pushes in (presses) the sides of the
box. As the pressure decreases they will spring outwards. This movement
is magnified and communicated to a pointer by a system of levers.
Some aneroid barometers are self-registering (they are called barographs).
Instead of a pointer a lever is moved. This carries an inked
stylo, which moves over a roll of paper fixed to a drum which is slowly
turned by clock-work. In this way continuous records of the atmospheric
pressure can be taken for periods of a week or longer.
Atmospheric pressure not only varies with altitude but also with
time. Although the time variations are small and do not follow any
regular law, they can be and are used by the weather bureau for predicting
weather conditions. When the barometric pressure begins to
fall, it is a sign of changing weather. If the pressure goes on falling rain
usually follows. As the storm passes, the barometer rises again. So,
watching the changes of barometric pressure the weather for that place
can be forecast.
If you look at the dial of a household barometer you can see the
following readings: Very dry, fair, rain, much rain, change, stormy.