undertaken so as to come rightly under the head of practical
engineering. In 1803 a tunnel was built through very soft soil for the
San Quentin Canal in France. Timbering or strutting was employed to
support the walls and roof of the excavation as fast as the earth was
removed and the masonry lining was built closely following it. From
the experience gained in this tunnel were developed the various systems
of soft ground subterranean tunneling in practice at the present day.

The first tunnel of any extent built in the United States was that
known as the Auburn Tunnel near Auburn, Pa., for the water
transportation of coal. It was several hundred feet long, 22 feet wide
and 15 feet high. The first railroad tunnel in America was also in
Pennsylvania on the Allegheny-Portage Railroad, built in 1818-1821.
It was 901 feet long, 25 feet wide and 21 feet high.

What may be called the epoch making tunnel, the construction of which
first introduced high explosives and power drills in this country, was
the Hoosac in Massachusetts commenced in 1854 and after many
interruptions brought to completion in 1876. It is a double-track
tunnel nearly 5 miles in length. It was quickly followed by the
commencement of the Erie tunnel through Bergen Hill near Hoboken, N.J.
This tunnel was commenced in 1855 and finished in 1861. It is 4,400
feet long, 28 feet wide and 21 feet high. Other remarkable engineering
feats of this kind in America are the Croton Aqueduct Tunnel, the
Hudson River Tunnel, and the New York Subway.

The great rock tunnels of Europe are the four Alpine cuts known as
Mont Cenis, St. Gothard, the Arlberg and the Simplon. The Mont Cenis
is probably the most famous because at the time of its construction
it was regarded as the greatest engineering achievement of the modern