i 9 THE IMPROVEMENT OF RIVERS. 



All the gates were of timber, the two last being paneled. Where the gates are of 

 metal they require less power, being usually much lighter than corresponding sizes in 

 timber. 



At the Canadian lock at Sault Ste. Marie, above referred to, the electric motor used 

 to operate a leaf about 37 feet by 40 feet is of about 25 horse-power, and at the lock at 

 the same locality on the American side a hydraulic motor of approximately the same 

 horse-power is used for a metal leaf about 43 feet by 50 feet. At the Cascade locks 

 of the Columbia River, Oregon, a metal leaf somewhat similar in size was found to 

 require about 10 horse-power for its operation under ordinary conditions, and at the 

 large lock at Bougival on the Seine, near Paris, the hydraulic motor (consisting of a 







cylinder press attached directly to the gate) for operating a wooden leaf about 39 feet 

 by 26 feet can exercise a direct force of 14,000 pounds.* The amount of power required 

 will of course depend largely on the method and point of application. 



The spars and operating gear for river locks should, where exposed, be all de- 

 signed so that they can be detached without difficulty and carried out of danger from 

 high water. Where this has not been done, damage from drift has frequently 

 resulted. 



Gates for Large Locks. The question of the design of gates for locks of unusual 

 size was taken up in 1899 by a Commission of Engineers, for the United States Gov- 

 ernment, in connection with the surveys for a proposed ship canal between the inland 

 lakes and the Atlantic. f The widths of the proposed locks were 60 and 80 feet, and the 

 lifts from 30 to 41 feet, with depths on the sills from 21 to 30 feet. This required some 

 of the gates to be designed for possible heads of over 70 feet, far in excess of any yet 

 employed. The investigations therefore were exhaustive, and the results are the more 

 valuable as they combine international opinions and practice. 



The most economical rise of sill was found to be about one-fifth of the chamber 

 width, or about twenty-one degrees. The ordinary mitering type was adopted for the 

 gates, as it possesses more than any other the merits of reliability, simplicity, and 

 strength, and steel was selected for the material, wood being inapplicable to the 

 conditions. The pure arch form, which has hitherto been principally used for wide- 

 span locks, was discarded in favor of a girder section with a straight down -stream face 

 and an up-stream face straight for about one-third of its length, and then curved in 

 toward both ends. The middle was made 4 to 4$ feet wide, and the ends about 

 2 feet wide. Comparative estimates showed that an arch would not save more than 

 10 per cent of weight, while it would possess the disadvantages of being much more 

 expensive in manufacture, and of having less stiffness and strength to withstand 

 shocks, since its section would be thinner than that of the girder gate. It would also 



* Annual Reports, Chief of Engineers, U. S. A., etc. 



t Report of the Board of Engineers on Deep Waterways between the Great Lakes and the Atlantic Tide- 

 waters^Washington, D. C., 1900. Appendix on Lock Gates by Henry Goldmark and S. H. Woodard, 



