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ENGINEERING WONDERS OF THE WORLD.
THE ROTARY OPENING UP A CUT.
THE ROTARY ENTERING A CUT.
switchback thrown across the range for opera-
tion during the construction of a tunnel. On
this part of the line 4 per cent, grades and
sharp curves were numerous, and drifts had
accumulated to a depth three or four times
that of the rotary. This last fact made it
necessary to advance the plough a few feet,
and then withdraw it and allow snow to
slide into the cut before attempting another
attack. After a leg of the switchback had
been cleared the rotary had to be taken to
the foot of the mountain, and headed by a