Ellsworth American., 1915-11-03
THE CANAL SLIDES.
Not ssShdes'' Strictly Speaking, but
Bulges from the Bottom.

Bu1ges from the Bottom.
lwiilis Fletcher johnson In Boston Trow-
scrtpt.l
Isthmlan nature is getting the bulge on
the Panama canal. Purists in speech will
please observe that the expression 10 not
slang. 1t is literal description OF the
disasters in the Gaillard cut, formerly
Culebra cut. Men speak Of "slides", and
slides there have been and are, and per-
haps will be. But these are not the most
serious Of the troubles. It is not that
earth and rocks from the sides OF the cut
ting slip down into the bed of the canal,
but that the bed OF the canal itself literally
bulges up, like . volcano island thrown
up from the floor Of the sea.
This extraordinary phenomenon is made
possible by the peculiar geological struc-
ture Of the Isthmus. There is fairly stiff
and stable crust. But beneath IL 10 q stra-
tum Of unstable material, almost in q state
OF fux. The great cutting Of the canal at
Culebra severed the surface crust, and
left the under stratum free to ooze up,
under the pressure of the neighboring
hills. Consequently the floor of the canal
bulges up, and the sides bulge in, and the
channel is blocked; now perhaps for some
months. A homely illustration OF it may
be made with q pie, with an upper crust
and Q mass Of soft mincement or what not
beneath it. Cut strip out Of the crust,
and scoop out the mince for half its
depth; and then press upon the remain
ing crust near the side of the cutting. The
mince will instantly bulge or flow forward
and I'LL up the little trench. That, on q
gigantic scale, is what is happening at
Culebra.
When our engineers first took hold OF the
canal, eleven years ago, they were
troubled with some actual slides; masses
OF earth anc rock from high up on the
banks becoming detached and slipping
down into the cut. That was because the
French had made the sides of the cut too
steep, and also because OF a lack of
conference and strength in the rock and
soil formation. The cure for it, as was
confidently expected, was partly in max
ing much iatter slopes, and partly cover
ing the slopes with vegetation, the dense
root masses OF which would form a strong
SOD and thus would give the soil coher-
ence. This theory was correct as far ss it
went. Mere sloughing off of earth and
rocks from the upper parts Of the banks
would never have been formidable, and
could have been overcome in the way sug-
gested.
An entirely different problem was
recognized, however, when the bulging
processes began in the very bottom Of the
cut and at the base instead of the crest OF
the side. Then it was fondly imagined
that this was made possible by the fact
that the cutting was empty and there was
nothing but atmospheric pressure to hold
the soil in place. When water was let in
its weigh would be almost as great, depth
for depth, as the earth which had heen re-
moved, and its pressure would, it was
hoped, assure stability to the floor and
sides. But this hope has not been full
filled. The bulging continues, in spite
OF the water. Indeed, it is believed that
the bulging is worse with the canal filed
thdh IL Wodid IL thC CuL WCIC cupby dHu
dry. And the bulging becomes more and
more extensive. Months ago there were
blockades which could be dredged away in
a few days. Nov there is talk of weeks
and of months Of complete suspension Of
traffic, with not the slightest assurance
that within twenty-four hours after the
reopening of the canal another and still
worse '.slide" will not occur.
The problem is really one OF the most
embarrassing that the engineers have had
to deal with in the whole course OF the en-
terprise. 1t is the only one in which they
have been confronted with an entirely un-
known and practically unknowahle factor.
For while the general principle of tn Q
"slides" is known, as we have explained
it, the extent to which the process may
continue is not known and can scarcely
be ascertained. Nobody can calculate how
many million cubic yards OF soft material
there is beneath the surface crust, nor how
much Of it will yet be forced out by the
pressure OF the adjacent hills. 1t would
be discouraging to think that we should
have to keep dredging out the ooze until
the hills had sunk to the level of the
canal; for, seeing that some OF the hills
which are near enough to exert pressure
upon the walls and floor of the canal prism
are two or three hundred feet high, that
might mean the dredging out Of as much
material as has already been taken out in
the whole enterprise. Whether it would
be possible to provide the canal with an
artificial lining which would restrain
the bulging is highly problematic. A
complete tube can be thus lined without
difficulty, because there is pressure on all
sides of it. But thus to line the bottom
and two sides of ditch which at the top
is open would be very difficult and
probably impossible thing.
In these circumstances it is natural to
recall the old "Battle of the Levels", and
to discern in them arguments in favor of
both sides. The advocates OF the present
high level and lock system may point out
that had the cut been carried down q