Evening star., 1900-12-10
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ITS VARIED USES
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Compressed AiraHas Already Accom-
plshed Wonders.
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A SIMPLE AND 81 PRACTICAL FORCE
Of Great VaIaeoin All Kinds of
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Undergroilnd Work.
F FUTU RE POS SIBILITIES
4 SIMPLE AND i :. PRACTICAL FORCE
F UTURE POS SIBILITIES

| Not satisfied with Harvesting electricity
| and forcing steam to serve his ends, man
! has at last shackled the very atmosphere
| he breathes and compelled it to do his
| work. The cheapest of natures products
| has now become the most valuable. Com
| pressed air has already accomplished mar
| vels and at this date only little is known
OF its eventual possibilities 1t is ventilat-
Ing the mines Of Pennsylvania. propelling
street cars in New York city and forward
| ing mails in Berlin. 1t drills holes in the
diamond mines of Kimberley and rings the
| chimes of ST. Patrick's Cathedral in New
York city. 1t polishes the walls Of weather.
beaten buildings and paints their interiors.
1t closes doors, sweeps carpets and builds
bridge foundations far below the surface of
! the water. S
| The compression of air Is very simple and
also very ancient. 1t dates back to the
air appliances Of Ctesibus. about $50 B. c.
| Not until 1910 was a practical air COM
| pressor built however, and this was the
| basis Of the present system of operation by
| compressed air. An air compressor con-
sists of cylinder of cast or gray iron; in
which piston moves to and fro. When
| the piston moves in it congresses the air
| within the cylinder against one end That
| Is the entire secret of air compression.
Steam, water other power moves the
piston. After the piston has done it's work,
the compressed air is forced through a
valve into. pipe leading to a tank or reser-
voir., In cases where great pressure is re-
quired, the air is forced into another cyfn-
der where 1t Is still further compressed.
| Then it passes to third cylinder where it
| receives its final compression.
Cooled and Heated.
Under great pressure air generates a
high degree of heat. and In order to obviate
danger from this cause all modern air COM
pressors are surrounded by coils of pipe
through which cold water runs in steady
stream. This serves to cool the machinery
and also the air. The latter, however, is
again heated before being used, as COM
pressed air does one-third more work when
heated.
When the air Is first released from the
reservoir where 1t has been crushed into
the smallest possible space it is dead and
relastic. This is due to the fact that tie
confined quarters of the Individual mole
cules constituting the air do not permit
them to move about. AS soon as heat is
/ introduced the air Becomes elastic again.
The most important to which COM
pressed air is put is IN the propulsion Of
cars and vehicles. In this system the car
carries it's own motiYe power in steel tubes
beneath the seats.
Compressed Air Cars.
Paris has the most extensive system of
compressed air cars. Next comes that Of
the 2Sth and 10Th street crosstewn lines III
New York city. The plant for compress
ing the air used on these lines is situated
at oath street and Hudson river. The air
compressor is probably the largest in the
world. The engine operating it is of 1000
horse power. The fly-wheel Is twenty-five
feet in diameter and weighs l2OOO pounds
There are four cylinders In the COM
pressor. In the firstrrthe air is compressed
to 40 pounds to the square inch; in the sec
ond to $50, in the third to $50 and in the
fourth to 2,:D0. The engine and COM
pressor, which are in one, are sixty feet
high. In the storage station are six hum
dred cylinders of the finest nickel steel
tested to withstand pressure OF 1900
pounds to the square inch. Into these re-
ceptacles air is forced and kept until need
eG. & 5..r
When a car is ready for a trip its tanks
(beneath the seats) are connected with the
steel cylinders bicycle pump is con-
nected with the tire. The air is turned on.
and in a few minutes the car Is ready TO
start. Thus supplied each car can travel
fifteen miles without recharging. For
wardng mail through pneumatic tubes is
another valuable application of air force.
Many Of the large citices of this country
transfer mail by the pneumatic system,
which Is almost instantaneous
In Mining Operations.
Great success has attended the use Of
compressed air in mining operations Not
only does the compressed air renew the vi
tally of the vitiated atmosphere in the bow
els of the earth, but in many mines it oper-
ates the rock drills, the elevators, the cars.
A good example Of this subterranean
work can be found in the construction OF
the underground rapid transit road in New
York city. At the upper end of Union
Square the contractors have erected huge
air compressor, which operates the drills,
hauls the dirt out Of the excavations,
freezes the quicksand, furnishes fresh air
to the workmen and pumps the water out
of the tunnels. The men working In the
tunnels use pneumatic tools. pneumatic
hammer. a miniature rockdrill, as 1t were
work of six armed with
ordinary tools. Pneumatic chfsels and au-
gers are also used.
Varied Uses of Air Force.
Another remarkable use for compressed
air Is to paint houses. The great apprais-
ers' stores In New York city and the main
buildings at the Chicago worlds fair were
painted by means Of liquid paint forced
through the nozzle Of tube by means of
air pressure. In this manner one man can
do the work of a dozen old-fashioned paint
ers. A variation Of this is to polish the
surface Of weather-beaten walls. In place
of the paint very fine, hard sand Is used
The tremendous force of the air blows the
sand against the walls with such power
that the friction produces high polish.
What will probably interest the housewife
most is the pneumatic carpet sweeper and
duster. Instead of Scraping along the car
pet. missing two-thirds Of the dust and
dirt, the pneumatic sweeper blows the
refuse into convenient receptacle, whence
1t can be removed at leisure.
/ All those who have Travelled on railroads
have been saved discomfort and danger
by the air brake. which Is now in almost
| universal use. This same principle that can
stop an expires strain within few hundred
feet can also play the chimes of st. Pat
! rick's Cathedral: The chimes weigh $500
pounds. and when first installed were
played by electricity. Owing to the uncer-
tainty OF the current and the proclivity
of the apparatus for getting out Of order
| some other motive power was sought
Finally compressed air was selected. Elec-
tricity is still used as the communicating
agent between the keyboard in the church
and the belfry. The air is compressed in
| the two towers, and Is released by the cleo
trlcity. whereupon the hammers drop upon
| the bells. and the, chimes send their melo-
dies into the world. The adr is also used to
produce sound in the great organ.
For Practical Purposes.
In Australia compressed air has been en-
ployed in depriving sheep Of their woolly
| covering. The shearing machine is some
what similar to the clipper used in every
barber shop: The difference is in the ma
nipulation. Instead OF being operated at
dignifed speed by the hand Of the operator