A Train Entering a Tunnel
Imagine yourself seated in a luxurious air-conditioned dining
car enjoying a delicious breakfast of bacon and eggs, toast and
milk, while your train speeds merrily along hundreds of feet underground.
This is happening every day in parts of our country where railway
tunnels pierce great mountain ranges.
Many passengers entering and leaving New York City pass directly
under huge ocean liners steaming to and from their piers on the
North River. In Washington passenger trains pass through a tunnel
that carries them almost directly beneath the Senate Office Building,
the Supreme Court Building and the Library of Congress.
The tunnel ranks with the bridge among the most interesting
features of the railroad. There are more than 1,500 railroad tunnels
in the United States, ranging in length from a hundred feet or
less to several milescarrying railway traffic beneath city
streets and skyscrapers, under busy rivers and harbors, through
hills and beneath rugged snowcapped mountains.
The tunnel is the direct opposite of the bridge. The bridge
carries the railroad above the earth's surface; the tunnel carries
it beneath the earth's surface. Both are difficult and expensive
to build; therefore, both are avoided whenever possible. There
are many instances where tunnels are necessary to provide a more
direct route between two points than would otherwise be possible,
to enable the railroad to traverse mountains at fairly level grades,
or to gain favorable entrances to large cities and obtain adequate
terminal areas in those cities without seriously disturbing surface
The first railroad tunnel in America was built in 1833 to carry
a railroad line through the Allegheny Mountains in Pennsylvania.
In the years that followed many other tunnels were opened.
All of them were eclipsed by the Hoosac Tunnel, more than 25,000
feet in length, completed in 1875, to carry a railroad line through
Hoosac Mountain in western Massachusetts. This tunnel is still
Since 1900 two longer railroad tunnels have been built in this
country. One of these is the Moffat Tunnel, carrying a railway
line for more that 32,000 feet through James Peak in Colorado.
This tunnel was completed in 1928. At its highest point, Moffat
Tunnel is 9,257 feet above sea level.
The other tunnel, the longest in the Western Hemisphere, is
the Cascade Tunnel, 41,152 feet in length, piercing the Cascade
Mountains in the State of Washington. It was completed in 1929.
The most stupendous tunnel project in the history of American
railroading, from the standpoint of total cost, was the twin-tube
tunnel under the Hudson River and the four-tube tunnel under the
East River in New York, together with terminals and yards under
the rivers and under the teeming city itself. This project, completed
in 1910, employed many thousands of workmen and great quantities
of equipment, tools and machinery. It cost in the neighborhood
of 113 million dollars.
The construction of a great railway tunnel calls for engineering
skill of the highest order, for an error in reckoning might prove
extremely costly. In the construction of the Cascade Tunnel boring
through solid rock was carried on from both the eastern and the
western portals. When the construction forces met, each nearly
four miles from their respective portals, the engineers found
that they were only a fraction of a foot out of perfect alignment.
This small error in reckoning was easily rectified.
Many tunnels are bored through solid rock by the aid of pneumatic
and electric-drills and explosives. A temporary railway track
is extended from the portal into the bore as fast as the drilling
proceeds, and this is used to carry off loose rock and boring
dust. It is also used to transport workmen, equipment and materials.
Electric fans or ventilator pipes keep fresh air circulating in
the bore. Pumps draw off seepage water.
Some tunnels are built for one track only, others are built
for two or more tracks, depending upon anticipated traffic and
other operating conditions. Many tunnels are lined with concrete,
brick or timber, or a combination of these materials, and many
are made waterproof to prevent seepage. Linings strengthen the
walls and ceiling and increase the safety of train operations.
Many railroad tunnels are electrified, and trains are operated
through them by electric locomotives.
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