FISHWAYS 99 



l 



it has been used in Europe to a considerable extent, there are only 

 a few installations in this country. It possesses many advantages 



PIG. 49A. Dam of Wasmngton Water Power Company, Showing Arrange- 

 ment of Rolling Gates. 



over other types of flood gates on account of the larger size in 

 which it can be built. For example, rolling dams have been built 

 in Europe with lengths up to 115 feet and depths of 28 feet. 



3. FISHWAYS 



In many States the law demands that dams be provided with 

 means whereby fish can easily ascend and descend according to 

 their natural habits in search of spawning grounds and of food. 



Many different designs, of more or less value, are in use, 

 the illustrations in Fig. 50 showing fishway recommended by the 

 New York State Conservation Commission. This type is termed 

 the Improved Coil Fishway, and consists of a number of compart- 

 ments arranged in steps and separated by cross-partitions. These 

 are provided with orifices, alternating from side to side, through 

 which the fish may pass from compartment to compartment, 



