REPORT 01? BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 8

 into account the short navigation season at the St. Marys Falls Canal, the tonnage per month during the navigation period of 1905 was three times as much through the Poe lock alone as at Suez.
 The Suez Canal is traversed almost exclusively by seaginig ships making long voyages, and therefore of large size. The average measurement of the 4,237 vessels passing in 1904, about 2,700 tons net register, is more than six times that of the vessels passing through the Manchester Canal to its terminus in 1900, and about sixteen times that of the vessels passing through the Kaiser Wilhelm Canal during the last year. It is about 50 per cent greater than the average tonnage of the vessels passing the St. Marys Falls Canal during 1905, but only 10.5 per cent greater than the average of those passing the Poe lock. The portion of the tonnage through the Poe lock which is carried in vessels equal to or ex eeding the average measurement of the ships passing the Suez Canal is largely in excess of the total tonnage at Suez.
 Finally, the aggregate tonnage passing all the four foreign canals above mnention1ed is much less than that passing' the St. Marys Falls Canal, and is even less than that passing one only of the three locks in use there. The average tonnage of the vessels in these foreign canals is but little more than one-fourth the average of those passing the St. MlarNs Falls Canal and -but little more than one-sixth the average of those passing the Poe lock. With these facts in mind there can be no need of further argument that Shis canal, although neither end touches salt water, furnishes abundant proof of the suitability of a canal with locks to serve a great commerce carried in ships of any size.
 The duplicate locks of the Panama Canal will afford convenient passage for an annual net registered tonnage of 80,000,000, as shown in more detail in Appendix L.

 SAFETY OF LOCKS AND OTHER STRUCTURES.

 The most plausible arguments advanced by advocates of a sea-level canal to justify its greater cost and the greater time required to build it are the alleged danger of carrying away the lock gates at either end of the summit level if a ship moving at speed should strike them, and the possible damage to structures through malice or in time of war.
 An accident to gates, if it occurs, is most likely to result from a mistake in the engine room, the engineer sending the vessel ahead when the pilot signals to back, and then the pilot, noticing that the ship's speed is not being reduced and not realizing that the previous signal is not beingcarried out, signals for full power or perhaps signals so rapidly that hie can not be understood. One or the other of these successions of events has usually taken place when a ship has run into lock gates. The carrying away of a lock gate occurs but rarely, but it has occurred three tImies in the Manchester Canal. It has never occurred in the St. Marvs Falls Canal.
 In the Manchester Canal the gYates at the lower end of the lock were struck, the upper gates being open, the ship moving downstream, but in all cases the operating force was able to get the gates at the head of the lock closed, or so nearly closed that they came together and held back the water in the canal. If such an event should occur at Panama, where the locks are in duplicate, traffic through the injured lock would be suspended until repairs could be made. With duplicate gates in stock the repairs could probably be made and traffic resumed through the injured lock without a prolonged delay. In the meantime, traffic would be continued through the duplicate lock, and although, if the traffic were great, it would be subject to some inconvenience, yet it would be maintained.
 if, however, the gates supporting the summit level should be carried away and the current flow unobstructed through the locks with no -means in readiness to stop it, such, for example, as a movable dam, the result would be very serious indeed. It would require many days to lower the level of Lake Gatun sufficiently to render the task of closing the opening through the lock easy, and in the meantime the channel and the works below the lock might be seriously damaged and navigation suspended for weeks or months. The chances for such a disaster are so small that if the Panama Canal were intended for commercial purposes only, the great additional expenditure required to make it a sea-level canal would have few advocates, but the possible need