The Best Isthmian Canal
WHILE the importance of connecting the seaports of our Atlantic and Pacific coasts by a short water route has been long appreciated in a general way, it needed the exciting incident of the passage of the Oregon around Cape Horn to develop a strong popular sentiment on the subject. The demand would naturally have been limited to the best possible ship canal, leaving the question of route to be determined in the usual technical manner; but, unfortunately, remembrance of the disastrous failure of the old Panama Canal Company ten years ago, and total ignorance of the work accomplished by the new company, were widespread through the country, and it was currently believed that that route had been proved to be impracticable, and that Nicaragua afforded the only possible solution of the problem. Having personally traversed both routes, and given over three years to a professional study of the details of one of them, I may be pardoned for believiug that these circumstances have placed us on the verge of a very serious mistake in this important matter.
The question is now narrowed down to selecting the better of two possible routes, — that by Panama and that by Nicaragua. Their respective merits have received technical discussion, and the following natural advantages possessed by Panama over Nicaragua will hardly be disputed by persons conversant with the subject. (1) Good natural harbors, familiar for many years to navigators, opposed to artificial harbors, one of which at least will demand constant outlay for maintenance. (2) A land route less than a quarter as long ; a summit level to be surmounted of only about half the height, involving only half the number of locks. (3) Curvatures more gentle than on any existing or projected ship canal, contrasted with curves too abrupt for rapid passage. (4) Far less danger from earthquakes than exists in Nicaragua; no troublesome winds or river currents to be encountered ; much less rainfall where heavy excavation is demanded. (5) And finally, location in a single country where every interest will favor the canal, and thus render its protection against malicious injuries far easier than in Nicaragua, where for many miles the route lies close to the border of two states which are often hostile, and are always jealous of each other.
There are besides economic considerations, such as very considerable progress in actual construction, — about two fifths of the canal bed is actually excavated ; important facilities for completion, including a parallel railroad, numerous quarters for laborers, many locomotives, dirt cars, dredges, excavators, and other tools on hand. At Panama there is a fortunate absence of the troublesome engineering problems which beset the way in Nicaragua, such as the maintenance of the level of the lake, a vast inland sea, within the narrow limits of six feet, — and this notwithstanding natural fluctuations about double that amount, due to phenomenal evaporation and very heavy rainfalls. This regulation of level is absolutely necessary, on the one hand to avoid drowning valuable private property on the border of the lake, and on the other to maintain the depth needful to navigation over the rocky bed of the San Juan River, which constitutes an important part of the route for shipping. Another great difficulty is to prepare appropriate foundations for the dam at Boca San Carlos, at about one hundred feet below mean water level, — and this in a great river a third of a mile wide, that cannot be temporarily diverted during the progress of the work. Last, but not least, there is the advantage of vastly less cost for operation and maintenance when completed. As to all these matters there is absolutely no contention possible between the two routes. It appears, judging from recent discussions, that the advocates of the Nicaragua route appreciate these facts, and now put forth only two claims that come fairly within the province of an engineer. These are : (1) that the distance between our Atlantic and Pacific seaports is considerably less, and hence that the time of transit must be materially less, by the Nicaragua than by the Panama route; and (2) that the trade winds on the Pacific are more serviceable to sailing ships, and will favor their passage by Nicaragua more than by Panama. These claims will now be considered.
The latter may be conceded, but is entitled to little weight. Very few sailing ships pass through any existing canal. That class of vessel is not suited to navigate contracted channels, and greater or less facilities for approach would not be likely to exert a controlling influence between two routes, one of which is short, and the other long and difficult. The relative cost of towage would have to be considered, and would probably decide the choice. As to the actual facilities for approach, Admiral Walker covered the ground in his testimony before the Senate Committee on Interoceanic Canals, on May 11, 1900. He said : " Between Colon and Greytown, for sailing ships, there is not very much difference as to winds; but between Panama and Brito the advantages for a sailing ship would be decidedly with Brito ; ” adding, “ The shipping in these days is going to steam, so that the question of wind is of very much less importance than it was fifty years ago.” It would appear that the least of the Panama advantages enumerated above should outbalance this questionable one on the side of Nicaragua.
The other claim, that there would be an important gain in time for our coastwise steamers by the Nicaragua route, is worthy of careful investigation. The first element to consider is the actual relative distance. The following figures have been stated on the authority of Commander Todd, of the Hydrographic Bureau of the Navy Department, the unit being the statute mile : New York to Colon, 2281 miles; New York to Greytown, 2372 miles ; New Orleans to Colon, 1589 miles ; New Orleans to Greytown, 1448 miles; San Francisco to Panama, 3777 miles; San Francisco to Brito, 3109 miles ; New York to Honolulu via Panama Canal (47 miles), 7699 miles; New York to Honolulu via Nicaragua Canal (190 miles), 7438 miles.
From these data it appears that the gain to a steamer in a voyage from New York to San Francisco via Nicaragua would be 434 miles ; from New Orleans to San Francisco, 666 miles ; and from New York to Honolulu, 261 miles. Assuming an average sea speed of 10 knots (11.5 statute miles), these gains in time will be 37.7 hours, 57.9 hours, and 22.7 hours respectively. It remains to inquire how much of this seeming advantage will be offset by longer delays in traversing a canal via Nicaragua than one via Panama. Such delays result from lockages, and from difficulties in maintaining full speed arising from curvature, strong winds, and local currents, if such exist on the route.
The delays to be caused by lockages in the two canals raise the question of the total height to be overcome. For the Nicaragua route, nature has fixed this at the level of the lake, about 107 feet. For Panama, it is a matter of choice, to be determined within the limits of economical excavation by the parties in interest, but it will always be less than 107 feet, — a fact of much more importance than the original heights of the divide, so often quoted. The new Panama Canal Company, contrary to what has been repeatedly asserted, has adopted a single definite projet, but one carefully adjusted to permit a decision as to the height of the ultimate summit level to be deferred until progress in the construction shall make known which of two heights is preferable. These two heights are 102 feet and 61 feet, the latter to attain 67 feet in great floods of the Chagres, which occur only at long intervals. The higher level has been adopted provisionally, to guard against interest costs resulting from any delay in completing the cut at the Culebra; but if the United States government adopts the route, the lower level will doubtless be given the preference, and it will therefore be assumed in the following comparison : —
Delays from lockages result from two causes: (1) loss of time consumed in actually raising and lowering the ship, and (2) loss of time in the needful preparations for so doing. The former admits of exact estimate, based on experiments at our great lock Poe at Sault Ste. Marie, and confirmed by experience there and on the Manchester Ship Canal. The limit of speed in raising and lowering which is found to be safe is two and a half feet per minute. This calls for 86 minutes for overcoming the ascents and descents on the Nicaragua route, and 49 minutes for those via Panama. The delays in the needful preparations depend on the number and adjustment of the locks. Careful observation of the passage of great ships through the Manchester Ship Canal has furnished the following figures, including the slackening of speed in approaching the lock, delays in entering and making fast, time spent in manœuvring the gates, delays in unlashing and leaving the lock, and time lost in regaining full speed. For each passage of a single lock these delays aggregate 21 minutes; and for two locks in flights, 30 minutes. On the Panama route there will be five locks, four of them disposed in flights of two. On the Nicaragua route the Walker Commission propose ten single locks. These data give the following as the total loss of time in lockages in traversing the two canals : via Nicaragua, 8 hours and 26 minutes ; via Panama, 3 hours and 32 minutes : gain for Panama, 4 hours and 54 minutes.
The speed which can be maintained in traversing the water way will be governed by the dimension of cross section, the curvature at changes of direction, the force and direction of the prevailing winds, and the currents when any are to be encountered. Experience on existing ship canals has also shown that a limit is imperative to protect the banks from erosion. This limit is generally fixed at 6 knots (6.7 miles) per hour. Another important element in determining the practical rate of transit is the length of the levels between the locks; for if short a high speed cannot be attained in traversing them. The routes will now be compared as to these elements.
In the matter of dimensions of cross section both conform to modern requirements ; in all other respects Panama possesses great advantages.
For facility in navigation an absolutely straight canal would, of course, be the ideal one; but such perfection is hardly to be attained in practice. The canal which most closely approximates to it, or, in other words, which has its route determined by curvatures of the longer radii, has obvious advantages in respect to ease and safety of operation.
On the Panama route the minimum radius of curvature is 1900 meters, and only one per cent of the entire distance between oceans approaches this limit (2078 yards). The ruling radii are 3000 or 2500 meters (3281 or 2734 yards), and 42 per cent of the route lies between these limits ; 57 per cent follows straight lines. For Nicaragua, the report of the Walker Commission is not very definite as to this important element. It gives (page 16) 1000 yards as the minimum curvature in the canal proper, but does not specify what it is in the 57 miles of the crooked San Juan River; where Lull’s survey, adopting the five cut-offs planned by him, indicates for the deep water channel six curves with radii between 233 yards and 1500 yards ; fifteen curves, between 500 and 833 yards; and twenty-one curves, between 833 yards and 1170 yards. Many of these curves have hills abutting on one side or both. The total change of direction in the entire distance amounts to 4607°, or about 13 complete circles. This matter of curvature is of immense practical importance. The Suez Company has been compelled, since the canal was opened to traffic, to increase its radius from a minimum of 700 meters to a minimum of 1800 meters (736 yards to 1968 yards).
In conducting a ship through a canal or narrow river, where currents are to be overcome, or where strong winds are to be encountered, either blowing across the route or acting from the rear to force her from her course in passing curves, the difficulties and risks of navigation are vastly increased. In this respect there is absolutely no difficulty on the Panama route. In Nicaragua ships must navigate for 57 miles the crooked San Juan River, which must carry the greater part of the lake drainage, and which traverses a gorge that Admiral Walker states is swept by strong trade winds during the greater part of the year.
As to length between locks on the Panama route, there is only one level (1.3 miles) less than 15 miles in length. On the projet of the Walker Commission the following lengths appear : 3.5 miles, 4.6 miles, 0.8 of a mile, 0.9 of a mile, 1.9 miles, and 2.4 miles.
In view of these facts, it would appear reasonable to accord an average speed of transit to the Panama route equal to that authorized by existing canal regulations (6.7 miles per hour), especially as for some miles in Lake Bohio it can be largely exceeded. The Nicaragua route is manifestly subject to unusual difficulties. On the Suez Canal, in 1898, the average rate of speed was only 5.5 miles per hour, and this with curves of nearly double the radius of those projected for Nicaragua, and with no winds or currents to cause delays. It would seem a very liberal estimate to accord an average speed of 5 miles per hour, allowing full sea speed (11.5 miles) in the 58 miles of deep lake.
Adopting these figures, we find for the relative times of transit by the two canals the following figures : —
|By Panama, 46 miles at 6.7'miles|
|Loss in lockages||3||32|
|Add 20 % for contingencies||2||05|
|Time of transit||12||39|
|By Nicaragua, 132 miles at 5 miles|
|58 miles at 11.5 miles per hour||5||03|
|Loss in lockages||8||26|
|Add 20 % for contingencies||7||58|
|Time of transit||47||51|
These figures, allowing full speed by night, show that a steamer crossing the Isthmus from ocean to ocean will require 35 hours more time if going by way of Nicaragua than if going by way of Panama. This practically offsets the seeming advantage of Nicaragua, given above, due to shorter ocean routes. In other words, a steamer leaving New York via Panama is really 12 hours nearer Honolulu, and less than three hours further from San Francisco, than if she went by way of Nicaragua. Even as between New Orleans and San Francisco the advantage of 666 miles in favor of Nicaragua counts for only 23 hours in time. Such gains are unworthy of serious consideration in voyages of this length ; but even they are overstated. Further allowance must be made for increased probabilities of detention, arising from inferior harbors, and from having to traverse a land route four times as long, and a much longer part of it by night (as must be done if the transits are to be made in 48 hours and 13 hours respectively). No attempt will be made to assign a numerical value to this additional loss of time, which may vary between wide limits in different transits of the Isthmus ; but evidently the loss via Nicaragua will be very important, and it much more than covers the insignificant gains indicated by the above figures. As a matter of fact, the advantage as to time lies decidedly on the side of Panama.
In fine, this claim of gain of time by Nicaragua must be relegated to the class of visionary arguments so often advanced to offset the solid merits of the Panama route. It is certain that if we are to have the best possible canal to connect our coasts, one not liable at any time to be superseded by a rival with which it could not compete, it must cross the continental divide at Panama. Nature has so decreed, and it is idle to contest the decision.
Henry L. Abbot.