The Panama Canal

by Duncan E. McKinlay

The Two Types of Canal

The difference between the two types of canal is this: A sea-level canal contemplated an excavation from shore to shore at the level of the sea; a lock canal contemplated the construction of a great dam across the valley of the Chagres and the course of the Chagres river, which dam would have the effect of holding the waters of the Chagres river. The accumulation of those waters in time would form a lake, the surface of which lake, of course, would be considerably above the level of the sea on either side. The dam would necessarily have to be surmounted through the agency of locks.

After much controversy and bickering, and a great deal of muck-raking by the newspapers and magazines of the United States and Europe, the plan of a lock canal was finally adopted. This plan contemplated the impoundment of the waters of the Chagres river by a dam constructed at Gatun, a little village about three and one-half miles inland from the shore of Limon bay. This dam when finished would be 7700 feet in length, half a mile in width at the base, and 135 feet in height. It was designed that this dam should hold the waters of the lake at a height of 85 feet above sea-level, but it was constructed 50 feet higher so that all danger might be obviated in case of excessive floods.

AT WORK IN THE CULEBRA CUT.

AT WORK IN THE CULEBRA CUT.

The plan of the canal contemplated that this dam should be surmounted by three locks constructed in pairs, so that in case one series of locks became impaired the other could be used, or ships might pass up one side and down the other at the same time. Each of the locks was to be 1000 feet long, 110 feet wide, and have a lifting capacity of 28½ feet. Therefore, when completed, this series of locks constructed of concrete would be more than 3000 feet in length and about 250 feet in width, without doubt the largest concrete formation ever constructed.

The engineers of the Panama Commission give four reasons for the adoption of the lock system instead of the sea-level type. In the first place, it would take twice as long to construct a sea-level canal as it would a lock canal. Secondly, it would cost twice as much money, and as the lock canal system is costing nearly four hundred millions of dollars, the difference in cost would be a great obstacle to the construction to the other type of canal. The third reason was that in case a sea-level canal was constructed it would be necessary to place locks somewhere along its course because of the fact of the variation of tides between the Atlantic and the Pacific Oceans.

The tide rises and falls at Colon, on the Atlantic side, about 3½ feet, at the time of extreme high tide; while on the Pacific side the tides rise and fall 27½ feet, and this great variation would cause a current to rush through the course of the canal so great that locks would be required for its control.

But the fourth was the most potent reason of all why the lock system was adopted. On the Isthmus of Panama the rainfall amounts to 130 to 150 inches annually. Sometimes the precipitation will amount to 10 or 12 inches in twenty-four hours. The Chagres river is the only agency for the drainage of a vast area of water-shed in the Caribbean sea. Therefore, at times the Chagres river might be a small, inconsequential stream that a boy could wade across, and yet before twenty-four hours had elapsed, because of a heavy rainfall, it might have swelled into a raging torrent that would wreck the strongest battleship of the American navy. The large volume of water discharged by the Chagres river could not be turned into the canal proper, as the currents and the rush of flood waters would soon impair the banks of the canal.