The Washington herald., 1913-03-23

times 1t has moved across and complete
ly closed the drainage channel in the
center. Over 100000 cubic yards have
been taken out Of this slide since the
American work began. and the slide II
still moving and the steam shovels are
still digging away at its front
No Slides in Rock Hills.
The highest elevations along Culebra
Cut are at Gold Hill and Contractors
Hill The rock of these hills has never
shown any tendency to slide, but the
most serious slide on the cut occurred
directly next these hills. 1t il supposed
that the heat Of the eruptive material
| forced up when the hills were in the
making in prehistoric times weakened
the rocks on either side and rendered
them liable to slip. Just north Of Gold
Hill there are enormous slides on both
banks of the cut On the side next Gold
| Hill Is slide which started two years
ago and has been increasing and extend
ing farther back ever since. Another
| break occurred early in 1911, which ex-
tended the back Of this slide more than
LOO feet from the center line of the
canal and increased its area to seventeen
| acres
| On the opposite Of the cut, at Culebra
village. is another slide, which now covers
|
| end. either. for the earth has cracked
and moved for a considerable distance
| farther back. From these two slides
| alone about 100000 cubic yards have
already been removed. and more than
100000 cubic yards are stin in motion.
Earth Moves Like Glacier.
These are the biggest of the slides
I The others are all small In comparison,
lalfhOnuh in ha
idea of the smaller slides may be given
by description of the slide which took
place near Las Cascades This slide be-
gan motion in August. 1908. but for time
moved unusually slow. This movement
continued for a period of three years and
extended back to a distance Of 80 feet
until about eight acres OF moving earth
and rock were involved. When II did
finally start on its downward plunge the
huge mass of earth and rock flowed for
ward like glacier clear to the center Of
the canal.
The occurrence Of slides in the earth on
steep slopes Is a common thing on great
engineering works. The slides of rock.
however. Is very rare. The causes OF the
breaks and slides which have occurred
in the Culebra Cut are Of much interest
Nearly all the rock in Culebra Cut disin-
tegrates when exposed to the air. GeoIo-
glsts say II is weakened by seams and
fractures and some OF IL SO soft that II
can be picked to pieces with the fingers
One of the greatest causes OF slides IN
the past has been the occurrence Of thin
seams Of Ignite, usually only a few
inches thick and very slippery. On the
east side OF the cut the dip OF the rock
Is toward the cut. 80 that wherever a
seam of this Ignite occurs the rock above
tends to slide down into the cut on the
slippery slope formed by the Ignite. Fre-
quently. when sudden movement oc-
ours and the slide gets the upper hand,
they have come down 50 rapidly as to !
bury steam shovels, wreck trains and
kill men working on them before they
could be moved out OF the way. Now
the engineers are having a strict watch |
kept of the mace of the mountain. and |
when stones and pieces OF dirt begin to
rattle down the shovel is moved at short |
notice. Oftentimes the slide will hang
and threaten to come down suddenly |
but it may remain that way for days at |
a time.
Francis r. Weller. a prominent engi- |
neer of Washington. said that the larger |
part OF the material in the slides Is |
earth, and yet there is a good deal of |
rock also in motion. He claims that the |
falling of this solid rock into the canal
prism when filed with water will make