JOINT SESSION OF SECTIONS D AND I.

THE QUESTION OF ISTHMIAN TRANSIT. By Commander H. C. TAYLOR, U. S. Navy, Poughkeepsie, N. Y.

[ABSTRACT.1]

REFERENCE to the three routes considered, Nicaragua, Tehuantepec and Panama.

Brief description of Panama canal and its present condition; work done, debt incurred.

Proposed plan of ship railway across Tehuantepec, brief description. Advantages of Nicaragua discussed.

Development of Central America.

Establishment of industries.

The international question.

Neutrality of the canal.

Possible aggression of powerful maritime nations.

The relation of the United States to the canal in the future.

THE ENGINEERING FEATURES OF THE NICARAGUA CANAL. By Civil Engineer R. E. PEARY, U. S. N., Washington, D. C.

[ABSTRACT.]

THE Nicaragua Canal is known by name, probably, to ninety-nine out of every hundred persons in this country; but the revised route, the en. larged capacity and the new features presented as the result of the last survey, made two years ago by the United States government expedition in charge of Civil Engineer Menocal, United States Navy, are not so well known and of them I will speak. The distance from ocean to ocean by the proposed route is 169.8 miles. Of this distance, however, only 40.3 miles are actual canal, the other 129.5 miles being free navigation through Lake Nicaragua, the Rio San Juan and the valley of the San Francisco. Beginning at the port of Brito on the Pacific side, the canal ascends the valley of the Rio Grande by four locks, and cutting through the low "divide" enters Lake Nicaragua 17.27 miles from Brito at an elevation of 110 feet above the sea. The route then extends across the lake, which is 40 miles wide and over 90 miles long, to its outlet into the Rio San Juan, a distance of 56 miles. Then down the broad deep reaches of the majestic San Juan to the dam, 64 miles from the lake. This dam, 1,255 feet long and 52 feet high, backs the water of the river the entire distance to

1 This and the three following papers will be printed in full and can be had from the authors.

the lake and makes it simply an extension of the lake. On the north bank of the river just above the dam a short section of canal, less than two miles long, cuts through the hills into the Y-shaped valley of the Rio San Francisco lying north of the San Juan and separated from it by a range of hills. An embankment 6,500 feet long and 51 feet high in the centre, built across the stem of the Y, floods this valley to the level of the water above the dam and makes about ten miles of lake navigation. At the eastern end of this lake commences the eastern division of this canal and pierces the "divide" by a cut 14,200 feet long and averaging 149 feet in depth. At the eastern end of this cut is the upper lock of the Atlantic flight. From here the canal descends the valley of the Deseado by three locks to the sea level and stretches across the lagoon region back of Greytown to the harbor eleven and one-half miles distant. From the last lock to Greytown, the same as at Brito on the west side, the canal is enlarged, forming an extension of the harbor eleven and one-half miles inland. The lake and river must form a part of any and every canal route through Nicaragua, and the location as a whole is the result of Civil Engineer Menocal's complete and exhaustive personal knowledge of the entire country from ocean to ocean, gained in the course of eight different surveys extending over a period of fifteen years and supplemented by a conscientious study of all that has been done by others in that region. Of the 40.3 miles of actual canal, about twenty-seven miles will be excavation pure and simple, while the remaining thirteen miles will be largely if not entirely excavated by dredges. With the convenient dumping ground for earth excavated, with a large portion of the rock from the summit cut utilized close at hand in the construction of the locks, the dam across the Rio Grande, and in pitching the slopes of the canal, and a still larger quantity to be consumed in the construction of the breakwaters at Brito, the work in this section admits of the most economical execution. The "divide" cut from the basin of the San Francisco to the upper lock, 14,200 feet in length and with an average depth of 149 feet, is, it is admitted, a very serious job, but with the neighboring streams offering water at a high head for removing the surface earth by hydraulic mining, with a large plant of power drills worked by compressed air, from the same source, and the use of modern explosives to remove the rock, with a large proportion of the excavated rock to be used in the construction of the locks and the damn, and in pitching the slopes of the canal; and a still larger quantity utilized in the construction of the harbor at Greytown; with the laborers above the miasma and mosquitoes of the swamp and exposed to the pure breath of the "trades" the work can be done without serious difficulty.

There are two features of this project which to many who have not made such structures a study cause a question of safety to arise; one is the dam, which at one stroke gives us sixty-four miles of river navigation, and the other is the embankment, which at a second stroke gives us over eight miles of lake navigation and completely solves for that portion of the canal from the dam to the "divide" (thirteen miles) the important problem of

protection from surface drainage, but neither of them is anything more than "small potatoes" when compared with many others scattered about the world and serving much less important purposes than those under consideration, and beside the Quaker bridge dam they are pigmies. Right here at the Croton reservoir is a dam which is to-day standing twice the strain that either of them will ever be called upon to resist. The locks are magnificent structures of concrete 650 feet long, 80 feet wide, and 30 feet deep, capable of containing any merchant vessel afloat, except the Great Eastern and possibly the City of Rome. The necessary machinery for moving the locks and culvert gates, for hauling the ships in and out of the locks, for electric lights and other purposes will be worked by hydraulic power furnished by the locks themselves.

In regard to the general question of locks the late Colonel John C. Stevens, for many years president and chief engineer of the New Jersey Railroad and Canal Company, and justly regarded as the most eminent canal engineer in this country, said in an article published in the American Engineer of Jan. 30, 1885:

"Locks are absolute sources of safety. A sea-level canal being sunk below the level of the surrounding country thereby becomes a drain, and is necessarily subject to all the risks from water that such a location entails, however skilfully the plans may be designed and the earthworks constructed. Unknown and uncertain risks must be assumed and the chances taken thereon. The precise amount of these will vary, but under the best conditions they may be appreciable, while under those that are unfavorable they will be such as to seriously impair the value of the work as a reliable channel of trade. The adoption of the lock system raises the canal above the ordinary drainage, and thus materially lessens the dangers which arise from that insidious enemy, water; and if the canal is well located they can generally be entirely removed."

And the same distinguished Ashbel Welch, to whom Colonel Stevens refers, says: "An artificial strait, a water course without impediment and all such phrases have a magnificent ring, but to spend millions of dollars for an idea or to satisfy an unreasoning or an uninformed public opinion is bad engineering. That is the best engineering, not which makes the most splendid, or even the most perfect work, but that which makes a work that answers the purpose well at the least cost. The demand of the public for a canal without locks reminds one of Charles Lamb's youthful Chinaman, who for want of knowing any cheaper way burned down his house to roast his pig." Again, "as for accidents, there is less danger with suitable appliances than on any other 1,000 feet in the canal, for vessels are under more perfect control." Stephenson, the celebrated English engineer, says: "It is a curious fact illustrative of the strength of prejudice that when Whitworth proposed to form a lock at Leith in 1786 it met with strong opposition on the ground of its being dangerous to shipping." And he adds, "such an objection, it is almost needless to add, is never now heard of."

To-day not a vessel discharges at Liverpool or Havre that does not pass through the dock gates, which is equally or more difficult than entering a lock, and I could fill a page with a list of French and English ports at which every vessel must pass through two locks before she can reach the quay to discharge. Much has been said about the harbors at the termini of the Nicaragua route, but neither time nor space will permit me to enter into the discussion here. It may be said, however, that there is no practical route for a canal across the American Isthmus that has good harbors, and it is believed that those at the termini of the Nicaragua canal can be made first class at less cost than those of any other route. There is nothing more difficult in the improvement of Brito Harbor than has been successfully accomplished at numerous French and English breakwater protected ports and harbors, and the maintenance of the harbor of Greytown will be a much less serious job than is the maintenance of the Port Said entrance of Suez, with the enormous silt discharge of the Nile driven across its mouth by strong littoral currents.

Lake Nicaragua has a surface area of some 2,000 square miles and a drainage area of not less than 8,000 square miles, and the Rio San Juan, its only outlet, discharges at its lowest stage, near the close of the dry season, eight times the maximum supply required by the locks. An inexhaustible supply of the best building material, such as lime, natural cement, stone and timber, can be obtained on the line of the canal, and with an abundance of palm leaves for thatching, such temporary buildings as are required for the accommodation of the working force and the protection of property can be constructed at little more expense than that of handling the material.

At Suez the traffic has been seriously delayed by the dimensions of the canal and the inadequate number of the turnouts. In the present project, not only have enlarged prisms been provided for, but large basins are proposed at the extremities of the locks. These basins, the enlargement of the canal at each end, with the lake, the river, and the San Francisco basin, will permit vessels to pass each other without delay at almost every point on the route. In 22.37 miles, or 57 per cent, of the canal in excavation the prism is large enough for vessels in transit to pass each other, and of a sectional area in excess of the maximum area in the Suez Canal; the remaining distance in which large vessels cannot conveniently pass each other is so divided that the longest is only 3.67 miles in length; that, with two exceptions, those short reaches of narrow canal are situated between the locks and can be traversed by any vessel in less time than is estimated for the passage of a lock; consequently, unless a double system of locks be constructed, nothing will be gained by an enlargement of the prisms. In the lake and in the largest portion of the San Juan River vessels can travel almost as fast as at sea. In some sections of the river, and possibly in the basin of the San Francisco, although the channel is at all points deep and of considerable width, the speed may be somewhat checked by reason of the curves.