cubic yards of material, which developed during the dry season and were composed wholly of material so dry that when loaded on the trains the cars were almost hidden during the windy season by clouds of dust. One of these slides was moving on surface which had a slope of one vertical to six horizontal, and its rate of advance was about two and one-half feet per day for several months. A steam-shovel made 103 cuts across the toe of this slide with the position of the loading track unchanged."

**

But while the slides have been an annoyance and have added heavily to the task in hand, they have been of great value in demonstrating the utter impossibility of constructing a sea-level canal across the Isthmus, thus vindicating the wisdom of the minority members of the International Consulting Board and the foresight of President Roosevelt, Secretary Taft, and the first Canal Commission in favoring and securing the adoption of the lock plan now nearing successful completion. A sealevel canal would cost billions of money, Scientific American, November 9, 1912.

in all probability would never be completed, and if completed could not be kept open for navigation. This is the united opinion of the engineers on the Isthmus.

The great feature of the constructive part of the work has been the Gatun Dam and the locks connected with it. No part of the great project has been more furiously or more ignorantly assailed and none has been more ludicrously misunderstood. The majority of visitors from the United States and elsewhere who have been passing in great swarms over the Isthmus during the past two years or more have expected to see a dam towering more or less straight into the air for a distance of several hundred feet. What they see is a low-lying ridge which does not look in the least like a dam, but more like the sloping bank of a pond or river. James Bryce, the distinguished English author, traveller, and diplomatist, who visited the Isthmus in September, 1910, spoke of the canal project as the "most gigantic effort yet made by man on this planet to improve upon nature." No part of that

project is an improvement more in harmony with nature's work than the erection of this dam at the extreme southern point in the valley of the Chagres, where the encircling hills most nearly approach each other.

If nature had intended to place a great lake among the hills of the Isthmus at

By courtesy of the Popular Mechanics Magazine. Towing locomotives.

Panama, she would have put a barrier across the valley at this point. It converts the great valley of the Chagres into a huge reservoir which impounds all the water that flows into it, not only from the Chagres River, which is the principal source of supply, but from many other smaller streams. It is about a mile and a half long, measured on its crest, nearly half a mile wide at the base, about 400 feet wide at the water surface, and only 105 feet high, measured from mean sea level. Of its total length only 500 feet, or onefifteenth, will be exposed to the maximum water head of 85 to 87 feet. It is not one continuous dam but two separate dams, with a hill of solid rock in the centre, through which a spillway or regulating channel has been cut. One end of each

dam abuts against the rock and the other against the encircling hills of the valley.

The united dam itself has a central section or core composed of an impervious mixture of sand and clay, pumped by hydraulic process from the river bottom of the valley, held in place on both sides by thick walls or sections of earth and rock

brought from Culebra Cut. It contains about 21,000,000 cubic yards of material, about equally divided between core and walls. It is not only as solid as the everlasting hills, but more scientifically constructed than they are, more pains, if one may say so without irreverence, having been taken in its making. That it will hold water was demonstrated during the wet season of 1912, when the lake behind it rose to a level of fifty-seven feet, or within thirty feet of the maximum to be attained, and there was no sign of leakage either under it or through it. No apprehension is felt by its constructors that when the lake rises to its full height, as it will by the end of the present year, the dam will prove less impermeable or immovable.

There was rainfall enough during the last rainy season to have filled the lake to its maximum, had the work on the spillway dam and the top gates of the upper locks been advanced sufficiently to permit of it. The spillway dam, which at that time was only fifty feet in height, will be completed to its full height above sea level, and the top gates of the upper locks, which will hold back the waters of the lake to a point well above the top of the dam, will be in place and completed.

The spillway is a concrete-lined channel, 1,200 feet long and 285 feet wide, cut through the centre of the hill of rock in the middle of the dam. It is in the form of an arc of a circle, with the bend toward the lake, and is composed of heavy walls of concrete, comprising about 140,000 cu

bic yards, rising to a height of 69 feet above sea level, or 16 feet below the 85foot level of the lake. On its crest are 13 concrete piers, with their tops 115.5 feet above sea level, and between these will be suspended regulating gates of steel which will be moved by machines up and down on roller trains in niches in the piers. These gates are to regulate the water level of the lake in case it should rise above the maximum. With all of them open, they will permit of a discharge of water greater than the maximum known discharge of the Chagres River during a flood.

Adjacent to the north wall of the spillway there will be a passage for the transmission of water from the lake to turbines for the generation of electricity with which to operate the lock machinery, the machine-shops, dry-dock, coal-handling plant, and batteries, to light the locks and Canal Zone towns, and to operate the Panama Railroad. The water used for the purpose will be mainly surplus and will not interfere with the operation of the canal. A hydraulic station will be erected near the spillway dam capable of generating six thousand kilowatts.

The construction of the dam, so far as the placing of material is concerned, was completed several months ago. Its lake slope is being riprapped with rock which will withstand the effects of water, and its land slope is being levelled off. Nature is rapidly covering the finished portions with tropical growth and by the time the canal is thrown open to traffic all signs of construction will have disappeared from view. The visitor of the future will stand on its summit and ask, "Where is the dam?" If he recalls the fierce and persistent assault which was made upon both the site and the method of construction, an assault which endured for three years and attracted the attention of the whole world, he will wonder what inspired it. It was an assault as unreasoning as it was ven

omous. No weapon was too contemptible or too ridiculous to be used, and no ally too unworthy to be welcomed. Engineers who had advocated the sea-level plan threw aside professional etiquette and even professional pride, and sometimes openly, but oftener anonymously, gave the color of expert knowledge to gross and shameless misrepresentation. Every man with a canal plan or with an invention he wished to have adopted for canal work; every contractor whose bid

Vessel passing through locks.

had been rejected by the Canal Commission-all these were sure of a hearing in this chorus of misrepresentation and defamation.

No rumor was too ridiculous to be credited. An unconscious humorist, eager for journalistic fame, sent to an American newspaper a report that a great underground lake had been discovered under the Gatun Dam-and the newspaper published it, without hint of a grin! This feat excited the ambition of a rival, who was an equally unconscious humorist, and he, when an insignificant slump in one of the toes of the as yet unbuilt Gatun Dam occurred, cabled to New York and the world that the dam had "sunk." These two grotesque "yarns"-underground lake and sinking dam-coming one after