Page:Popular Science Monthly Volume 74.djvu/439

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then at his command, the president reached the conclusion that a canal with locks would best fulfil all requirements, and says in transmitting the board report to the Congress:

In my judgment a lock canal as herein recommended is advisable. If the Congress directs that a sea-level canal be constructed, its direction will of course be carried out. Otherwise the canal will be built on substantially the plan outlined in the accompanying papers, such changes being made, of course, as may be found necessary, including possibly the change recommended by the Secretary of War as to the site of the dam on the Pacific side.

When the matter was before the senate committee on inter-oceanic canals, another opportunity was provided for the expression of views by experts. At these hearings. Professor Burr said that he was as strongly in favor of the sea-level canal as he ever had been.

The more I reflect upon it, the more it seems to me that that plan is the one which the United States Government should adopt.

In discussing the Gatun dam, which is a feature of the lock-canal project as adopted, he says:

It is proposed to build this dam by simply clearing off the surface material and then spreading the earth, suitably selected from the canal excavation, in layers, and so building it up to a height of 135 feet, making its base something like half a mile wide.[1] In my judgment, that is a dangerous experiment on a colossal scale, which this government is not justified in undertaking.

Continuing, Professor Burr states that he has no objection to earth dams under suitable conditions if properly designed and founded. Anything like a flow of water through the permeable material under the dam should be prevented. No suitable means for accomplishing this are provided in this design. He indicates measures that are ordinarily taken to check the flow of water under a dam, and instances several failures of earth dams. In speaking of the dams near LaBoca resting against Sosa Hill, the construction of which was subsequently undertaken, but owing to the yielding, unstable character of the marsh lands on which they were to rest, have been abandoned. Professor Burr says:

The dams on the Pacific side are smaller, and the risks, perhaps, may be of less magnitude; but they are of the same character, and there is the same objection to them, in my opinion. This dam between LaBoca and the high ground opposite would be founded largely upon the most slippery kind of mud. Any one who has been there and has seen the bottom of the Rio Grande estuary exposed at low tide, I think will agree with me that it is a very lubricating material; and if you were to put a bank of earth on it, even if it were half a mile thick, I think it would be in great danger of being pushed out bodily.

In speaking of the operation of locks, he calls attention to the fact that the experience at the lock at St. Mary's Falls is not a safe guide for reaching conclusions regarding the safety of six such locks as will be required for the Panama Canal. Their lift is 50 per cent, greater,

  1. As now contemplated, the dam is to be constructed by the hydraulic fill method.