THE KEY OF THE PACIFIC.*
MOST of us are aware that the Nicaragua Canal is a work of great difficulty, but few really understand what the cutting of a canal from Greytown to Brito across the Isthmus means —a stupendous piece of canal engineering to which the Suez Canal is child's-play. The Suez Canal is a sea-level canal,. and a child digging a trench in the sea-sand with a. wooden spade does in miniature what Ferdinand de Lessepe and the Khedive did with the aid of the kourbash and. the corvee. The difficulty is the same with both, the shallow- ing of the waterway by shifting sand, and, therefore, the necessity of continuous dredging, that is the only true diffi- culty. It is not, then, strictly speaking, an engineer- ing difficulty, but is simply a question of money and patience,. and it is, of course, peculiar to the Suez Canal. The Panama. Canal was also supposed to be a sea-level canal, it was to cut sheer through everything, and the distance would be a little- over forty-six miles. At one point the height to be eat through was over WO ft. of most unstable rock, and it. is the Culebra Cat together with the Chagres River that constitute difficulties outside the range of practical 1 • The Key of the Pacific : the Nicaroyies Canal. By Archibald Ross Colquhoun„ F.R.G.S. With numerous Illus:raticor. Plan,„ and lisps. kudon : A. Constabw and Co.
engineering, according to Mr. Colquhoun, The Chagres River drains a basin of fourteen hundred square miles, and is liable to the most violent floods, and nowhere in the streams or torrents of Burmah or India or Indo-China had he seen a more formidable thing than the Chagres River. Yet Lesseps' canal, being at sea-level, was at the mercy of a tropical flood. This he afterwards saw, and locks were de- signed, but he would have had no means of supplying water to the highest level of the canal but by building reservoirs and pumping from them. We know the rest—half the money was stolen, Lesseps was not an engineer,—moreover he was an old man and had made his name,—and the Panama Canal, which might have been a monument to French enthusiasm, became a monument of official corruption.
Now the Nicaragua Canal is nearly one hundred and seventy miles in length, but there will be only some twenty- seven miles of excavated canal, the rest of the waterway being reaches of the San Juan River and basins made by dams in the Deseado and San Francisco valleys on the Atlantic side of Lake Nicaragua, and two sections of canal with an inter- mediate basin, on the Pacific side. Lake Nicaragua occupies the summit of the canal, the Bailing line across the lake being fifty-six and a half miles. Its highest water-mark is 110 ft. above sea-level and its area is four thousand square miles with a watershed of four thousand more. It has large out- lets, and the variation in level does not exceed 5 ft. There- fore it is not liable to sudden or great fluctuations in volume, and forms a magnificent reservoir for the whole canal. It is the absence of dangerous features that has led Menocal, the moving spirit in the great scheme, to contrive a plan by which so less than one hundred and fifty-four miles of the route is at "summit level," the level of the waters of Lake Nicaragua. The locks, only six in number, three on the Pacific side and three on the Atlantic, are close to their respective oceans, and do all the lifting—one lock lifts 45 ft.—and though this means a great pressure on the lower gate, it is not considered impracticable. The number of locks could be increased, there being plenty of convenient sites, but the fewer they are the less the cost of maintenance and the greater the economy ef time. How does Mr. Menocal propose to insure a high level waterway all the way from Lake Nicaragua to the highest lock on the Atlantic side? By building a series of embankments, as many as sixty it seems, across the intersecting valleys and dips, culminating in the Ochoa Dam below the confluence of the San Carlos with the San Juan, and so making a series of basins. The same is done in the Deseado Basin, thus keeping the canal at "summit level" right through the great divide cut to the highest lock. The success of the whole scheme depends on the Ochoa Dam, which is to be placed between two hills, and is to dam up the San Juan. The length of the crest of the weir is nearly a quarter of a mile, excluding abutments; it is to rise 70 ft. from the river-bed, and to be 500 ft. through at the base, and well it may. It is proposed to construct this dam by simply dumping boulders of varying size from cable- ways spanning the valley, and to fill in with smaller materials, such as gravel and clay, on the up-stream side. Menocal thinks that as long as he can preserve his high-level water- way it does not matter whether the Ochoa Dam is water-tight, indeed he thinks it would be safer if it were not. Major Dutton, whose report on the Nicaragua Canal is often quoted by Mr. Colquhonn, was struck with the idea of a Loose-rock dam,—it certainly has the elements of simplicity and boldness. The percolation of water does not necessarily endanger the dam, and provided the water has other outlets besides pouring over the top the wear and tear would not be too great for the crest of the dam. Major Dutton thought the strain, even when 8 ft. of water might be rushing over the weir, as nothing compared to what a breakwater of like construction at Holyhead has to stand from big Atlantic waves. That may be, but the Ochoa Dam is to us the weakest point of the ,canal. Not that it is inherently impracticable, for if the material of the dam gets firmly bedded on a good rocky floor it will hold. The completion of the great work, the same expert tells us, will be its success, as it will have to stand annual floods of some duration. We see no reason, then, why it should not stand when completed, but the con- struction will be tedious, and we are afraid that floods will cause much disappointment by destroying the beginnings of the dam. Even in India there is nothing quite com-
parable to it ; there are higher dams, but they are water- tight earthworks, with or without masonry shells. English
opinion, which is ever cautious, seems to be against the Ochoa Dam, and in Engineering we are told that, allowing regular lockages to go on every hour, it will make no appreciable difference to the San Juan River even in the dry time, and that the whole regulation of the water in that river will fall upon the dam, which must have a clear overfall in the dry time of more than a foot, and in the wet of 4 ft.,—in fact, that no "rubble dam," whatever the dimensions of the crest, could stand the spilling of such a volume of water over it. This opinion differs from that of Major Dutton and Mr. Menocal, and we think it is too sweeping; it has yet to be seen if such a dam could not last and could not be kept up by dumping fresh material, and so maintaining the level of the canal. The La Flor Dam is second only in importance as it will form the Tola Basin on the Pacific side of Lake Nicaragua ; its dimensions are even greater than the other, but it is proposed to build it with a solid core of masonry, and it will not have the pressure or the variation in pressures of the other.
The three great difficulties of the Nicaragua Canal are these, Ochoa Dam, the Divide Cut, and Greytown Harbour. There is no essential difficulty in the "cut," but the magni- tude of the boring and blasting work necessary to excavate a cutting three miles long, with an average depth of 140 ft., and 100 ft. wide at the water-line, means a heavy expense. Borings made at regular intervals have revealed as yet nothing of a dangerous nature in the stratification of the rocks, and the collapse of the Culebra cutting in the Panama canal can hardly be repeated. The walls, too, can approach the perpendicular if the rock is trustworthy, and that means a vast economy. A tunnel is also practicable. Greytown, the Atlantic entrance of the canal, is unfortunately situated in the very teeth of the North-East trade winds, and the sand silts up the harbour almost hourly, so to speak. The proposed breakwater would in time, we do not doubt, effect the saving of the harbour, but opinion generally is against the practicability of Greytown. Nor, with Engineering, do we doubt that if the stupid folly of meddlesome seventeenth-century idiotcy was repaired, and the San Juan allowed to resume its old bed, that the scour would keep open the channel. However, the Commis- sion which has recently reported will not look at Greytown.
The report of the Commission must not be received, as we fear it will be, as conclusively proving Menocal to be wrong and his critics right. We have not forgotten how the English engineers sent to report on the Suez scheme—with the brilliant exception of Hawkshaw—pooh-poohed it as an impossibility. Menocal and his assistants made a most careful survey, for with only twenty miles of artificial canal in the plan they surveyed four thousand, so as to master drainage, contour, and all points that concerned the effective- ness of the canal, and this sometimes through jangles that required the machete every foot, and sometimes through mud and water waist-high. So that we trust the average individual with common-sense will banish all comparisons with Panama from his mind. Why, the nature of the rock in the Culebra cutting was never ascertained, or even Lesseps might have hesitated, and the fact that he had imagined a sea-level canal to be possible, with a river like the Chagres ready to rise 40 ft., and so swamp everything and everybody, stamped the Panama project and its pro- jector as unscientific.
The original estimate of the expense of the Canal by Menocal, which was thirteen millions, has been nearly doubled by the Commission, and they are right, and for their twenty- six we should put thirty. Experience, as Mr. Colquhoun says, shows that the original estimates were exceeded in the case of the Suez and Manchester Canals by something like 300 per cent. We have never any difficulty in spending money on our little frontier warfares, and to suppose that the advance of a regular army of workers through a tropical marsh could be anything but a pouring out of money and a terrific waste of life, shows ignorance of climate and the adverse conditions under which machinery has to work.
Mr. Colquhonn has little doubt that the Nicaragua Canal is "the demand of the age," and that it is bound to be an accomplished fact before, shall we say, the middle-aged man reaches the allotted span of life. We have waited, he says, four centuries for it. David the Buccaneer is reported to
have said that he valued the treasures of Granada as but a barrel of wine compared to the knowledge he obtained of Lake Nicaragua and the possibility of controlling the two oceans. Humboldt, Goethe, and Napoleon M. have all prophesied vast potentialities. Nor can there be any doubt that the opening of the canal will counterbalance the enor- mous advantage the English have gained in the Suez Canal ; indeed, to use an Americanism, it will "go one better." It will give a great impetus to trade, and the easy connec- tion between the Pacific coast of South America and the Atlantic coast of North America will alone revolutionise American trade. Twenty-eight hours is allowed for transit of the canal on a reasonable calculation—two oceans in twenty-eight hours ! The Manchester Canal has come too late for Manchester—the palmy days of cotton-spinners are no more—but the Nicaragua Canal, though late, is not too late to bring a golden wave of prosperity that shall flood the Americas from Cape Horn to Alaska. The Atlantic States will be in touch with China and Japan, and thousands of miles nearer to Australia and New Zealand.
Mr. Colquhoun has not forgotten the State of Nicaragua itself, and his pen describes social and political Nicaragua every whit as clearly as it does the great problem of the canal. The State has great resources, mineral and vegetable, a large Indian population—docile and industrious—and a climate that will not decimate the workers as the Isthmus of Panama did in six weeks. The country itself cannot supply the workers, the Central American being less able even than his neighbours to endure physical labour, but the West Indies can, and as long as there is a negro left a dollar a day will bring him.
Menocal, the designer of the canal, must be a man after Mr. Colquhoun's own heart, and with plenty of the necessary -tact, and he ought, we think, to have a fair field and the money, if the jealousy of the 'United States will allow him both. Mr. Colquhoun's subject is so engrossing that we have only the space to thank him for a most masterly, thought- -fill, and moderate review of the canal problem as it is.
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