[Illustration: TRACING AND PROFILE OF THE PANAMA CANAL.] [Illustration: M. EIFFEL’S PROPOSED SLUICES FOR THE PANAMA CANAL.] The proposed modification of the original plans has been so designed as to enable the works of the tide-level canal to be continued without interruption. The lock canal was to be at sea-level from Colon to the fourteenth mile, where the first lock with a lift of 26¼ feet would be placed. The second lock with the same lift was to be placed 23-1/9 miles from Colon, and the third and fourth locks, with lifts of 36-1/11 feet each, at 27¼ and 28¾ miles respectively, making the summit-level 124⅔ feet above the Atlantic. The canal was to descend to the Pacific by three locks of 36-1/11 feet drop, situated at 35½, 35-9/10, and 38-2/5 miles respectively from Colon, and one lock of 26¼ feet drop at 36¾ miles, thus making up the difference in level of 134½ feet between the summit-level and low-water of spring tides at Panama. It has been suggested that in the event of difficulties occurring in the excavation of the Culebra cutting, the summit-level might be raised to 160¾ feet, by inserting a lock with a lift of 36-1/11 feet on each slope of the Cordilleras, whereby time might be gained by a further reduction in the amount of excavation. The section adopted for the level canal was to be maintained in each reach. The width of the locks was to be 59 feet, and their available length 590 feet. At the Colon entrance, the canal was to have a bottom width of 590 feet for 1·86 mile, and at the Panama end, 164 feet for 3¼ miles; whilst the channel in the Pacific, from the shore at Boca to Naos, was to be 164 feet wide. Allowing a speed of 6¼ miles per hour in the long reaches, and 2¼ miles in the short reaches, and one hour for passing through a lock, a single ship would traverse the canal in seventeen hours twenty-eight minutes, and in a convoy in twenty-eight hours twenty-five minutes. Accordingly, ten vessels, or 25,000 tons, could pass through the canal in twenty-four hours, so that, if necessary, 9,125,000 tons of traffic could be accommodated annually. The water supply required for this traffic was estimated at 1,050,000 cubic yards per day, which could be obtained from the Chagres, the Obispo, and the Rio Grande. With the summit-level at 124⅔ feet above the sea, it could be supplied from the reservoir created by the large dam at Gamboa; but if the summit-level was raised to 160¾ feet above the sea, pumps not exceeding 3600 H.P. would be needed for lifting the supply the additional height. The gates for the locks were designed to be hollow-iron counterbalanced caissons, suspended from a frame with rollers, running on a roadway supported by a swing-bridge across the lock, and continued above the recess at the side, into which the caisson was to retreat for opening the lock.