204 
REPORT ON THE PANAMA CANAL 
ground occur, warning is frequently given by the appearance of cracks 
peripheral to the coming slide. In some instances cracks exist for a 
long time before important movements take place. They are well illus- 
trated upon Culebra Hill, west of the great break. As soon as they are 
formed they should be filled up, in order that they may not intercept 
surface water and lead it into the sMe. 
3. Drainage of Undisturbed and Threatened Areas .-Undisturbed and 
threatened areas near the slides should be thoroughly drained both by 
surface and by tile drainage, to keep as much water out of them as pos- 
sible, for they may become unstable and they may supply water to the 
slides. The drainage water should be carried from the neighborhood 
of the slides as directly as practicable. Experiments with tile drainage 
on a small scale would soon show whether it is effective enough to justify 
its extension. The surfaces of the ground east of the East Culebra 
Slide and in places west of the West Culebra Slide, slope away from the 
adjoining slides, and the water can be readily removed. But a con- 
siderable area above the Cucaracha Slide drains naturally into it; some 
of the drainage can be diverted to the east, but the rest should, so far 
as possible, be collected by surface and tile drains, and be carried to the 
Canal through a large concrete-lined surface drain. 
4. Drainage of the Great Slides.— A complete system of open drains 
should be established on the great slides and the water carried away as 
directly as possible. The main drains should be made impervious on 
the Cucaracha and, so far as practicable, on the two Culebra Slides. 
5. Drainage by Tunnels. — Drainage by means of tunnels might be 
adapted to a few special cases, but should be tried with caution, and 
extended only in cases which promise results commensurate with the 
cost. The tunnels should be built underneath the sliding ground in 
the undisturbed material and strongly timbered so as to avoid risk of 
collapse, which would not only destroy the tunnel but would also dis- 
turb the overlying material. From the main tunnel smaller branches 
may be extended into the material to be drained and frequent borings 
made from the surface to conduct drainage water to the tunnels from the 
overlying strata. Such a system would be expensive, but might be 
effective in draining the area tapped by it. 
Relief of Pressure. — It is suggested that a cut be made by sluicing in the 
East Culebra Slide, starting at an appropriate point on the Canal, and 
diverting from it diagonally in a general southeasterly direction, in the 
zone of gentle slopes and in such a position as to reach the large pond 
which now exists on the slide. This cut would partly separate the 
roughly rectangular slide into two approximately triangular parts, and 
