t70 THE IMPROVEMENT OF RIVERS. 



of i in 34 and provided with six steps each 5 inches high, with slopes between of i in 

 40. The inflowing water, which was 4.6 feet deep at its commencement, was reduced 

 by velocity to a depth of 3.3 feet at the outlet. The chute is closed by a needle dam. 



The lock and dam were opened to navigation Feb. 22, 1899. 



Dam No. 3 at Libschitz. In this dam, where the lift is 12.7 feet, there are two 

 openings, a weir 160 feet long, with 10.4 feet on the sill, and a pass 213 feet long, with 

 14.7 feet on the sill. The weir is closed by means of needles 12$ feet long provided 

 with hooks which go over the escape-bars, as at the dam at Joinville-sur-Marne. They 

 are supported by trestles 4 feet apart, 13.7 feet high, and weighing with all attach- 

 ments 1400 Ibs. each. These trestles are formed of Manncsmann tubes, protected 

 when down by a sill i foot 6 inches high, the lowering being accomplished in the same 

 manner as at the Klecan dam. 



The trestles, of both the pass and the weir, are lowered towards the center pier, 

 which is composed of cut stone and is 19 J feet wide, with its coping 20 inches above pool. 



The pass is closed by wooden Boule gates, supported by trestles formed of channel- 

 irons. Five gates are used to each bay, four lower ones, each 3! feet high, and one 

 top one, i foot 7 inches high. The lowest gate is 5 inches thick. They are put in place 

 and maneuvered by a small traveling crane. 



The trestles are 4 feet i inch apart and 19.7 feet high, and weigh 2800 Ibs. each, or 

 with all attachments, 3740 Ibs. each. 



The rails for the service car are hinged to the top members of the trestles and carry 

 sheet-iron floors between, and form the connection between the members. The recess 

 of the sill is 3 feet 3 inches deep. 



The raising or lowering of the trestles is accomplished by means of a crab fixed 

 on the bank, operating a long steel chain which passes above the trestles and to which 

 each one is attached at the middle of its top member by a cast screw-clamp when its 

 turn comes for lowering. This clamp is bolted to the trestle and forms the surface 

 over which the chain slides, no sheave being used. The trestles are clamped 8 feet 

 apart on the chain and can be raised six at a time. They are 7 feet 4 inches wide on 

 top and provided with a hand-rail, and two widths of floor are used, one on each side of 

 the chain. By this means a double track is provided for the service cars. 



The lock and gates are similar to those at Klecan, but the filling-wickets slide 

 horizontally and are mounted on a truck with six wheels, to avoid sliding friction, 

 after the manner of a Stoney gate. The emptying wickets, which lift up, are simi- 

 larly mounted. All are worked by hand. 



A raft chute is provided of construction similar to that at Klecan, except that it 

 is closed by a segmental, counterbalanced drum shutter, like a Taintor gate, lowered 

 into a recess in the floor. This chute is 324 feet long, commencing with a four per cent 

 grade, reduced to one per cent, and is provided every 20 feet with steps 5 inches in height. 

 The work was completed in 1900. 



