Imágenes de páginas

Fig. 7. — Culebra Cut at Culebra, looking north from west bank, showing dredges at work on Cucaracha slide. Dredge in foreground is of suction type and discharges material through pipe line. Other dredges are of dipper type, depositing on scows. This is the final operation on Culebra Cut, and shows how canal will be cleared of possible future slides.

ments of relative advantages and disadvantages before them, which type was to be adopted.

The essential facts regarding the two types of canal can be most clearly set forth in a table such as the following, to which is added a third column showing the characteristics of the canal as actually built:

COMPARATIVE DATA Sea-level canal and lock canal as proposed by the Board of Consulting Engineers and canal as built.

[blocks in formation]

Includes sanitation, civil government, land damages and purchase price from French, not included in first two columns.

Not only was the sea-level canal of inferior dimensions and greater cost, but its winding channel would not be conducive to easy or safe navigation, and the time which a vessel in the high-level canal would lose in the locks would be lost in the sea-level canal in slowing down for passing other vessels on account of the very narrow channels; in fact, two vessels of any size could not pass in the 21 miles of 150-foot width unless one of them tied up in specially provided turnouts, similar to the custom in the Suez Canal. The sea-level canal was not considered superior from the standpoint of safety; the sinking of a single ship could block the canal indefinitely; the many stream diversions along the banks of the canal and the great dam at Gamboa were potential sources of danger in time of flood to a canal which was in the lowest part of the valley, and would form the receptacle for flood debris.

It is illuminating to read the following extract from the comment of Secretary of War Taft, on the report of the Board of Consulting Engineers:

The majority of the Board makes objection that locks are unsafe for the passage of the great seagoing vessels contemplated by the act, due to the disastrous consequences that might result if the gates are injured by vessels entering; that the lifts proposed are beyond the limit of prudent design for safe operation and administrative efficiency; that locks delay transit.

Lock navigation is not an experiment. All the locks are duplicated, thereby minimizing such dangers, and experience shows that with proper appliances and regulations the dangers are more imaginary than real. The locks proposed have lifts of about 30 feet, or less than those heretofore advocated by engineers of such high standing that the objection is believed to be not well founded. The delays due to lockages are more than offset by the greater speed at which vessels can safely navigate the lakes formed by the dams than is possible in the sea-level canal, and the argument on this point in the minority report seems to me to be the more weighty.

The advocates of the sea-level canal express doubt as to the stability of the dams at Gatun and at La Boca, if founded on the natural soil, and advance the opinion that "no such vast and doubtful experiment should be indulged in."

It appears, however, that the dams proposed are to be founded on impervious materials, thereby conforming to the views of the

majority, and are to have such ample dimensions as to insure the compression of the mud and clay rather than its displacement. Furthermore, the estimates include an allowance for additional safeguards against seepage if subsequent detailed investigations show the necessity for extra precautions. The construction of earth dams to retain water 85 feet deep is not experimental, and as the dams proposed have greater mass and stability than similarly constructed dams of greater heights, it appears that the apprehensions as to the safety of the dams are unnecessary.

When I visited the Isthmus a year and a half ago and went over the site and talked with the then chief engineer, I received a strong impression that the work of construction upon which the United States was about to enter was of such world-wide importance and so likely to continue in active use for centuries to come, that it was wise for the government not to be impatient of the time to be taken or of the treasure to be spent. It seemed to me that the sea-level canal was necessarily so much more certain to satisfy the demands of the world's commerce than a lock canal that both time and money might well be sacrificed to achieve the best form, and this feeling was emphasized by reading the very able report of the majority. But the report of the minority, in showing the actual result of the use of the locks in ship canals, in pointing out the dangers of so narrow and contracted a canal prism as that which the majority proposes, and in making clear the great additional cost in time and money of a sea-level canal, has led me to a different conclusion.

We may well concede that if we could have a sea-level canal with a prism from 300 to 400 feet wide, with the curves that must now exist reduced, it would be preferable to the plan of the minority, but the time and the cost of constructing such a canal are in effect prohibitory.

I ought not to close without inviting attention to the satisfactory character of the discussion of the two types of canal by the greatest canal engineers of the world, which insures to you and to the Congress an opportunity to consider all the arguments, pro and con, in reaching a proper conclusion.

The following is the essential part of the decision by President Roosevelt, dated February 19, 1906, which

« AnteriorContinuar »