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I had visited the Varina once, reaching her on the 3d March, Lieutenant Michler arriving in the latter part of the same day in the Bonga.

My examination of the valley of the Atrato leads me to venture the theory that it was originally a portion of the Gulf of Darien, which, by the gradual process of ages, has been filling up with the débris from the adjacent mountains. In this I am sustained, first, by the extraordinary depth of the river, which has not sufficient force of current to have cut for itself a channel of such a depth (it in some places exceeding 100 feet); the alluvial character of the soil, too, as anywhere exhibited, indicates comparatively recent origin; again, the waters of the Gulf of Darien are without current, except such as is imparted by the constantly outpouring Atrato, which, being fresh, is only on the surface, and this gulf receives annually a vast quantity of matter contributed by the hard winds and westerly currents of the Caribbean Sea, which are perpetually wafting organic substances towards the Gulf of Darien. To me it appears to be a very natural and simple theory that through these two opposing agencies the valley of the Atrato has been for ages the depository of mountain detritus and ocean drift.

The northerly winds blow quite fresh throughout the winter months, and, opposed by the current from the river, cause a rough sea across the entire gulf. The disturbing effects thus produced were constantly visible to us, and the changes are of daily occurrence.

On the numerous logs and snags which are strown over the flats outlying the mouths of the river the deposition rapidly forms islets on which vegetation soon takes, and I have more than once seen some of these islets rooted up from their anchorage and swept off into the gulf. The same changes may be observed about the mouths of the Mississippi, which are almost identical in character with those of the Atrato, and the utter failure thus far of all attempts to improve the bars of the Mississippi suggests to the mind that engineering science has not devised a method by which channels of even a very moderate depth may be cut in the more difficult regions of the Atrato.

PART II.—In this second part of my report I shall proceed, sir, to give an estimate of the amount of work and time required in the construction of a ship-canal connecting the waters of the Pacific Ocean with the Gulf of Darien, via the Atrato, Truando, and Nuquah Rivers. It has been proposed that an open cut, or a canal without locks, be made from the Atrato River to the Pacific; said canal to be 30 feet deep and fulfilling all the requirements of commerce.

Having given most careful consideration as to the necessary width of a ship canal which shall in every way fulfill the conditions required, I am of the opinion that the bottom width of said canal should not be less than 100 feet, which will be barely sufficient for giving surface width enough to allow two first-class vessels to pass each other at the lowest rate of speed. One of them, indeed, must lie against the bank while the other passes. (Ocean steamers are from 65 feet to 80 feet "over all.")

But as I am directed to make an estimate of the excavation required for a canal of 100 feet in width at the water-surface without its cost, I will give such estimates, although such work would be contrary to the laws of nature.

A canal dug in the most favorable condition of soil requires that its banks shall have a side slope of 2 feet base to 1 foot rise, or an inclination requiring 2 feet sectional width for a vertical rise of 1 foot, and, although the soil of the morass to be traversed by this interoceanic canal is far from being such as will admit of a rise so rapid, I propose, in the

following estimates, to adopt that slope, in order to place the subject on the most tangible footing.

With the foregoing requirements, I pass to the consideration of the amount of earth and rock excavation from the mouth of the Truando to the Pacific.

To facilitate these calculations, and also to place the matter before you in the most intelligible manner, I will divide the route as follows: Division 1. From the Atrato to the foot of the Rapids of the Truando; distance 38 miles, rise 173 feet; earth and mud excavation.

Division 2. From the foot of the Rapids to their head; distance 4 miles, rise 25 feet; rock cutting.

Division 3. From the head of the Rapids to the mouth of the Hingador River; distance 10 miles, rise 3 feet; earth and mud excavation. Division 4. From the mouth of the Hingador River to the Totumia, through the depression in the Cordilleras; distance 10 miles; average depth of cutting 180 feet; rock cutting.

Division 5. Through the Totumia to the sea (tide-water); distance 3 miles; rock and earth.

ESTIMATES.

Division 1.-Thirty-eight miles in length.

A canal 30 feet in depth, being an open cut, will, at the Atrato, be 30 feet deep; at the upper end of division, 473 feet deep. A side slope of 2 to 1 mile give a surface width, at lower end of division, 120 feet; at upper end, 188 feet.

Material to be removed, earth and logs:

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Cubical contents of excavation in Division 1: Cubic yards, 13,242,240.

Division 2.-Four miles in length.

Cutting 473 feet deep at lower end; 72 feet deep at upper end; ma terial, basaltic rock. In rock cutting we require, of course, very little slope, and in the following the calculation is based on a slope of 1 to 4 nearly. In order, therefore, to preserve the surface width of 100 feet, I

* A width at surface of less than 120 feet is not attainable, and I have already stated that I assume a slope more rapid than the soil will probably bear.

will, in the deep cuts, assume a bottom width of 85 feet, which, with the slope indicated, give a water level width of 99 feet. It must be remembered that in the rock we must have more room at the bottom, to avoid all risk of injury to the sides and copper of vessels from contact with the rock.

DIVISION 2.-CROSS-SECTION, LOWER END.

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Cubic contents of rock cutting in Second Division: Cubic yards, 4,721,728.

Division 3.-Ten miles in length.

Cutting at lower end, 72 feet deep; at upper end, 75 feet deep. The substratum of this excavation, say one-half, estimated as rock upper stratum, earth and mud.

The base of the earth cutting to be 10 feet wider on each side than the top of the rock cutting.

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Cubical contents of rock cutting: Cubie yards, 6,816,480.

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Cubic contents of earth excavation: Cubic yards, 14,289,440.

Division 4.-Ten miles in length; average depth of cutting, 180 feet; material, rock.

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Cubical contents of rock excavation in Fourth Division: Cubic yards, 45,760,000.

Division 5.-Three miles in length; average depth of cut, 30 feet deep to tide-water; earth and rock.

CROSS-SECTION OF CUT.

Area 1,800 square feet, 200 square yards.

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Cubic contents of earth and rock in Fifth Division: Cubic yards, 1,056,000.

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Very reasonable doubts must arise as to the utility of a ship-canal of only 100 feet in water-surface width. Independent of the impossibility of vessels passing each other is the important consideration of wear, there being so little space afforded for the transit of even moderately. sized steamers that the agitation of the waters must inevitably cause great damage to the banks and require the constant use of the dredging machine. No durability whatever can be expected in a canal so narrow without walling up its banks; the soil is such as to afford no stability for piles.

In a pecuniary point of view, the saving would not be commensurate with the sacrifice of width, as the more confined space for work will increase proportionally the cost of removing the material in the rocky portion of the route.

In order to permit vessels to pass each other, basins must be provided at proper and frequent intervals, say at distances of 3 miles apart. This would require twenty basins, which should not be less than 400 feet long, or an aggregate of 8,000 feet in length of basins, which may be roughly estimated at 1,701,216 cubic yards of additional excavation.

It must be understood that the canal projected will be about 65 miles in length. Allowing that vessels may traverse it at a rate of speed not exceeding 4 miles per hour (which will be the maximum speed allowable, and, indeed, too high a rate for works so insecure), sixteen hours will be required in making the transit from the Pacific to the waters of the Atrato, without taking into consideration the delays caused to such as are obliged to lie in the basins while others are passing. This delay would constitute most serious objections to the transit of a canal so

narrow.

But the brief time given me for the discussion of this reduced canal forbids my enlarging upon the many objections which suggest themselves to my mind.

The body of my report explains already the manner in which my survey was made. The distances given by me from the foot of the Palos Caïdos to the mouth of the Hingador are geographical, based on carefully established points, as named in the appendix. I give the distance by the general course of the stream, regardless of its numerous sinuosities, and nearly as a canal would be traced out. All other distances were carefully measured.

BREAKWATER AND JETTIES FOR ARTIFICIAL HARBOR ON THE PACIFIC TERMINUS OF THE CANAL.

In estimating the cost and length of time required in the construction of this essential part of the work, I shall be guided by the work already referred to in Plymouth Sound, though that is by no means a fair criterion of this work, as the structure made by the British Government was carried on under every advantage of available science and with conveniences not attainable on the Pacific coast.

Cost excluded, it will be found in my report opening an entrance into the Atrato from the Gulf of Darien.

I must confess myself utterly at a loss as to the framing of an idea as to the method by which this essential portion of the work can be accomplished.

Three miles of dredging are required, to the depth of 30 feet, through a soil of the softest kind of ooze.

When I consider that the best ability of our country has, as yet, failed to discover a means of deepening the bars of the Mississippi, it

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