M* THE IMPROVEMENT OF RIVERS. 



could easily maneuver a gate of 5.8 square feet under a head of ?J feet.* Ordinary 

 rollers were also experimented with, but gave less satisfactory results. The effort 

 required to lift the ordinary sliding gate under pressure reaches in certain instances 

 as much as 2000 pounds. 



Ijiirgc sluice-gates moving on rollers have l>een used in England since 1876, where 

 they were introduced by Mr. Stoney, an English engineer, and are known as the Stoncy 

 gate. They have been used up to 16 feet in width, some of the most recent exam- 

 ples being found on the great reservoir dams of the Upper Nile. 



On the Libschitz dam (Bohemia, 1900) with 14 feet 9 inches on the sill, the Botile 

 gates used were five in number for each bay, four being 3} feet high, and the top one 

 i foot 9 inches high. The woodwork of the lowest one is 5 inches thick. The trestles 

 are spaced ij meters apart, and are 19 feet 8 inches high, and weigh about 3000 Ibs. 

 each. The recess behind the sill is 3^ feet deep. 



On the Boul6 dam, at the head of the Louisville canal, Kentucky, which is at 

 present the only dam of its class in this country, the trestles are spaced 4 feet 



apart, and are 7 feet high, 

 and are composed of i"X4" bar 

 iron. The depth on the sill is 5 

 feet, and the lowest gate is j inches 

 thick. The dam consists of three 

 openings, each 200 feet long, and 

 one opening about 50 feet long. 

 It was built in 1899, and is used 

 as a flushing weir for the basin at 

 the head of the canal. 



On the Moskva, in Russia, a 

 combination of needles and 

 is to be found, constructed about 

 1876. The needles are placed 

 immediately above the trestles 



DAM COMPOSED OP BOULB GATES AND NEEDLES, AS USED ON THE and are suppO rted as usual, and 

 MOSKVA, RUSSIA. 



the gates, which are planks 9^ 



inches wide and of a length equal to the width between each trestle, are laid hori- 

 zontally, being supported by the needles instead of by the trestles. 



Remarks. The Boule gate has proved to be an excellent device, as it is simple, 

 and with proper appliances can be maneuvered under the full head of water. It is 

 also cheap in construction, as it requires no great width of foundation, having in this 

 respect an advantage over the Chanoine dam, which is almost always provided with 

 the service bridge for ojerating. Comparative estimates of the two types for the 



* Annalcs des Fonts ct ChausstVs, April, 1896. 



