There are at least five routes which at one time or another have been chosen and seriously considered as possible locations for the Isthmian Canal. They are: the Atrato-Napipi, the San Blas, the Tehuantepec, the Nicaragua, and the Panama routes.

The Atrato-Napipi route follows the river Atrato, which empties into the Gulf of Darien, as far as the mouth of its tributary, the Napipi, thence up that river through the mountains and empties in Capica Bay. See Fig.1, No. 1.

The San Blas route runs from the bay of the same name on the Atlantic side to the river Chipo which empties in the Gulf of Panama. It is only forty or fifty miles southeast of the Panama route. See Fig.1, No. 2.

The Tehuantepec route begins at the bay of Coatzacoalcos in the Bay of Campeche and ends at the harbor of Salina Cruz in the Gulf of Tehuantepec. See Fig.1, No. 3.

All modern engineers thrust these aside as impracticable, the first two because of the necessity for tunnels and the last because of its great length and number of locks. They will, therefore, receive no further attention.

The choice of the location for an Interoceanic canal has long been conceded by practical engineers to lie between the Nicaragua and Panama routes. A consideration of the natural advantages and disadvantages of these rival lines follows.

Since the Nicaragua route has been abandoned the features of the proposed construction will receive no attention. It is highly probable that this route would never have been seriously considered by the United States had it not been for the fact that the Panama line was for many years under the control of France and apparently was destined to continue so for a considerable period.

Logically the question of harbors first suggests itself. Natural harbors do not exist in Nicaragua nor could one be excavated and maintained on the Atlantic side without a continual battle with forces which, in the last fifty years, have transformed what was once an excellent harbor at Greytown into a lagoon partially enclosed by an ever advancing line of sand brought down by the river San Juan. Experience on the South Atlantic and Gulf coasts of the United States has given abundant evidence of the results of a fight with such forces. In his “The American Isthmus and Interoceanic Canal” W. Henry Hunter says, “The policy which fights against the forces of nature is a mistaken one; it is foredoomed to failure. Nature may be aided in her operations; her more gigantic forces may to some extent be curbed and controlled; but an almost certain Nemesis pursues any effort which may be made to arrest and to determine in an absolute way a process so continuous as that of the filling up of the Greytown bight.”

Brito, the Pacific terminus, is little better than Greytown since “even in the calmest weather there is a nearly constant surf, with breakers from four to ten feet high.” Therefore, the terminus at Greytown would always be in danger of being filled up by the Atlantic waves and the one at Brito would constantly be liable to destruction by the Pacific breakers.

On the other hand the natural harbors of the Panama route have successfully met the demands of commerce for the last four hundred years. On the Pacific end practically no harbor improvements will be necessary. On the Atlantic the present needs are satisfied, but the large steamers of the future may require deepening which can be done and the resulting channel easily maintained since there is no persistent filling in process such as characterizes the Greytown harbor.

Volcanoes have long been plentiful in Central America, especially near the proposed Nicaragua canal. Nicaragua Lake, so geologists say, owes its separation from the Pacific to a great upheaval. There is now an active volcano near which ships would have to pass. From January 1, 1901 to April 30, 1904, a period of forty consecutive months, the instruments of the Instituto-Fisico Geografico, located 60 miles from the locks of the proposed canal, recorded 43 tremors, 91 slight shocks and 35 strong shocks, some of which lasted 16 minutes. Similar observations at Panama for the same period revealed only 6 tremors and 4 slight shocks, the longest being for a period of only 10 seconds. The lock gates of a canal might very easily be injured by earthquakes; and common sense would dictate that other things being equal, the canal should be placed where the shocks are fewest. Strong trade winds rush through the San Juan gorge at all seasons. The rainfall near the Atlantic is enormous, averaging from 260 to 270 inches per year, and rain may be expected any day. In the western part the fall is only 65 inches, and there is also a well defined dry season. Clear vision is essential to safe passage through the canal and it is extremely doubtful if it could be obtained under the above conditions. Still more serious perhaps is the excessive curvature of the channel for 50 miles of its course. It is impossible to reduce the curvature to the limit which experience on the Suez canal has proved necessary for safety and speed. Furthermore the channel must carry off to the sea the drainage from 12,000 square miles of territory. This cannot do otherwise than create currents and eddies unfavorable to navigation.

The Panama route has no continued strong winds; the curvature is comparatively favorable; the annual rainfall is from 140 inches on the Atlantic coast to about 60 inches on the Pacific, with a definite dry season of three months; and the concensus of expert engineering opinion is that there need be no objectionable currents if proper provision is made for the regulation of the Chagres river. This phase will be discussed later as will also the question of curvature.

Much has been said about the advantages furnished by Lake Nicaragua which covers about 70 miles of the Canal route. However, for 29 miles of that distance, an artificial channel through soft mud would be necessary, and dredging would probably be practically continuous for maintenance.

From a purely engineering standpoint the most serious objection to this route is the liability to interruption for lack of water in seasons of extreme drought which are not at all uncommon in that region. Upon first thought it seems that a lake 3,000 square miles in extent cannot be other than an ideal source of supply, but such is not the case. By the proposed dam on the lower San Juan river the channel of the stream would become an arm of the lake through which all shipping would have to pass, the depth of water being, of course, dependent upon the lake level. This level has a natural variation of 13 feet. Under the projected conditions the whole outflow would pass over the dam about 50 miles away from the lake proper. The present high water mark cannot be exceeded without flooding valuable lands, nor, on the other hand, can the channel depth be made as great as desirable because the river bed is crossed by many rock ledges, and the cost of excavation fixes a limit to the depth economically practicable. The Isthmian Canal Commission of 1899–’01 concluded that the variation would have to be reduced to 7 feet. This means that the level would be held between 104 and 111 feet above tide water and the river bed excavated enough to give a minimum sailing depth of 40 feet. Records show no regular succession of high and low lake years; and as it is plainly impossible to keep a reserve sufficient to control such an enormous expanse of water, the regulation of this most important matter would be left to the judgment of the operator controlling the overflow at the dam. Carelessness or bad judgment on his part might therefore easily stop traffic for an indefinite period.

There is a similar question in regard to Gatun Lake of the Panama line although the majority of authorities anticipate no trouble from that source. A more complete discussion of this danger will be given later.

Concerning the actual difficulties of construction at Nicaragua, little need be said inasmuch as no work is now contemplated there. The San Juan dam of the Nicaragua and the Gatun dam of the Panama route both present conditions which have never been met before. Also the deep cuts of the Culebra find their counterpart in portions of the longer route.

The time-saving element is of more apparent than real importance because the time lost on the longer sea-voyage for the Panama route would be practically balanced by the gain of time in actual passage through the canal, the Nicaragua route being about four times as long as the Panama route. Henry L. Abbot, in his “Problems of the Panama Canal”, estimates that 34 hours more time would be required for passage by way of the Nicaragua than by way of the Panama route.

An excellent reason for the adoption of the Panama rather than the Nicaragua route was the existence of a good railroad and the fact that the French had actually completed about two fifths of the work required.

SUMMARY OF COMPARISON

Below is given a summary of the comparisons which have just been discussed.