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the Miraflores Locks for the small Miraflores Lake by a dam 2,700 feet long, which joins the west hill to the locks, and a concrete wing wall 500 feet long extending from the locks to the east hill. On this wing wall are erected regulating gates like those in the spillway of Gatun Dam, and the wing wall is thus made to serve as both dam and spillway.
OGEE CURVE OF SPILLWAY DAMS.
The concrete dams across the spillways of Gatun and Miraflores Dams are built on an ogee curve so that the force of the water will be broken as it rushes over.
Gatun and Miraflores Lakes.
Gatun Lake will extend from Gatun Dam to Pedro Miguel Locks, through Culebra Cut, a distance of 31 miles on the center line of the canal. It is formed in the basin of the Chagres River by raising the surface of the river to 85 feet above sea level. The water, therefore, will extend into every part of the valley below that elevation, make islands of what are now hills, and deep inlets of the scores of streams that pour their waters into the river. Its area will be 164 square miles, and it will contain two hundred and six billion cubic feet of water when the surface is at 85 feet above sea level. Every rainy season enough water is poured into the Chagres basin to fill the lake one and a half times. At the close of each rainy season the surface of the lake will be at 87 feet above sea level, and evaporation, use of water for lockages and electric power, and waste may reduce it to the 85-foot level before the dry season (January to May) is over. Throughout the dry season there is a considerable run-off in the Chagres River, and freshets sometimes occur; 80 that there will be a constant addition to the great storage reservoir even during th driest months, probably enough to counterbalance the evaporation, which is estimated at about four feet a year. The ship channel through the lake from Gatun to Culebra Cut varies from 1,000 to 500 feet in width, and necessitated an excavation along the course of the Chagres River of about thirteen million cubic yards.
Miraflores Lake will be a pond about 2 miles in area, in which will collect water used in lockages at Pedro Miguel Locks and the run-off of the Cocoli River. Its surface will be at 55 feet above sea level. The ship channel through this lake will be 500 feet wide and a little over one mile long.
The part of the Panama Canal on which most work has been done, and which will be the last completed, is the cut through the hills of the continental divide, known as “Culebra Cut." This section is 9 miles long, extending from the point where, in its descent to the sea, the Chagres River turns at a right angle from an easterly course to one almost exactly north, to Pedro Miguel Locks where the line of the canal runs into the valley of the Rio Grande. Excavation was begun here by the French on January 20, 1882, and has continued with only three years' interruption (1888–1891) up to the present time. The Bulletin du Canal Interoceanique (issued in Paris by the old French company) published the following cable message from Panama, under date of January 20, in its issue of February 1, 1882:
"The first work on the great cut of the maritime canal was formally inaugurated to-day at Empire in the presence of the dignitaries of the state, the leading citizens of the city, and the great assemblage of the people. The first locomotive has arrived at the newly opened excavation. The city of Panama is celebrating the event with a grand fete."
The French were working in Culebra Cut on May 4, 1904, with 700 men, when the United States Government assumed control. In this section they had excavated about nineteen million cubic yards of earth and rock useful in the present canal, leaving eighty-four million yards to be excavated under the American regime.
The digging here, as at other points, is done by steamshovels, and it is here that the superiority of modern methods of excavation
has been shown. Steam-Shovels. Forty-five steam-shovels dig, and load upon
cars, 60,000 cubic yards of material each 8hour day. This quantity is said to represent about 120,000 two-horse wagon-loads. Trains of 20 cars, each car holding 20 cubic yards of rock and earth, hauled by 100-ton. locomotives, carry away the spoil to be utilized in the dam at Gatun, the breakwater at the Pacific entrance, the new line of the Panama Railroad, or to dumps where it is.
CULEBRA CUT AT GOLD AND CONTRACTOR'S HILL-SUMMIT OF DIVIDE,
merely wasted. The method of work is to drill holes in the rock, fill them with dynamite, and then shatter the material into such fragments as a steam-shovel can handle. Four main lines of railroad track with numerous spurs enable an endless chain of trains to pass through the cut, to p beside shovels for their load, and when loaded pass out to the dumps.
The long trench is kept dry by two methods. Diversion ditches cn either side prevent water from the side hills
from flowing into the excavation. The digDrainage. ging is carried on from a center point or sum
mit on a downward slope toward either end of the cut. A center drainage ditch carries the water by gravity to a sump at the north end, whence it is pumped over a barrier into the Chagres River; and to Pedro Miguel Locks at the south end, whence it flows by gravity through the locks into the old channel of the Rio Grande.
A troublesome but not serious feature of the work are the slides from both banks, 22 in number, and in amount
about twenty million cubic yards. Masses of Slides. earth and rock, from which the supporting
toe has been removed by excavation, slide into the prism of the canal, and must be dug out. On account of these slides it may be necessary to excavate the last ten feet of the rock in Culebra Cut by dredges, after the canal is opened to navigation; but this will not be allowed to prevent the opening in 1913, although it may retard the actual completion. There are no ships in the Panama trade that could not use the canal with a minimum depth of 35 feet of water, and none in the American Navy that might not be taken through with perfect safety.
Supplies and Equipment.
Practically all the supplies and equipment in use on the Canal are purchased in the United States, because a law, passed by the Congress in 1905, makes home purchases obligatory, unless the President should deem prices asked by United States manufacturers exorbitant in comparison with those quoted in foreign countries. This law has had the effect of keeping American manufacturers within bounds in their bids. In only two cases has it militated against them-one in the purchase of the largest dredge in use on the Canal, which was built in Scotland at 50 per cent of the price asked by the only American bidder; and the other in the purchase of Mannesman tubes for the stems of valves in the lock culverts, after the only manufacturer of this class of material in the United States had arbitrarily increased the price with direct reference to the Canal work.
Under the law, any article or supplies of a value not exceeding $10,000 may be purchased in the open market without advertisement or bid. In practice this privilege is seldom used, and nearly all equipment and sup, lies are purchased on competitive bid, after due advertisement. The award must be made to the "lowest responsible bidder.” This system does not always procure the best machines or materials, but it is the most economical in the end; because any other would be a constant nuisance by giving endless opportunity for charges of unfairness by bidders, and of dishonesty by a vigilant and not overscrupulous sensational press.
In making purchases the methods long used by the United States Army, Navy, and other Government departments are followed. Since 1907 the administration has been able to determine from year to year about what amount of materials and supplies is necessary during the following year; and standard articles are purchased in sufficient quantities to last twelve months. The contract entered into obligates the contractor to furnish more of a given article up to 50 per cent, in case the Canal authorities so wish, and absolves the Canal Commission from purchasing within a certain per cent (usually 20) of the estimated amount required. Inspection of materials is made by the technologic bureaus of the United States Government, or, in case such knowledge is not required, by inspectors in the Canal service. Only materials that comply with specifications are accepted. All supplies are handled by the Quartermater's Department, Colonel C. A. Devol, Chief Quartermaster; Capt. R. E. Wood, Assistant Chief Quartermaster; Capt. C. Nixon, Depot Quartermaster.
It is difficult to find terms that will convey a true impression of magnitude where one is dealing with such quantities as are required in the canal work. One easily senses a barrel of cement, less readily a thousand barrels; but 4,500,000 barrels are beyond visualization. Broadly speaking, 3,500 barrels of cement were required every day while the lock building was at its height; and the delivery of this material from New York took all the time of two 10thousand-ton ships, and several smaller ones aggregating ten thousand additional tons. So with steel, dynamite, and other supplies; the amounts are so large as to mean little, because they baffle familiar comparison. In 1910, the year when the work was at its height, there were purchased 350,000 tons of materials, valued at $10,000,000.