I054 BULLETIN OF THE BUREAU OF FISHERIES. 



2. The fishway proper is 4 feet wide inside, with orifices in the cross 

 partitions varying from 12 inches by 12 inches at the outlet to 18 inches by 18 

 inches in the uppermost cross partition near the inlet, allowing fish of the size 

 of shad, rockfish, salmon, etc., as well as smaller fish, to pass through. 



3. The mean depth of water in the compartments is 3 feet. 



4. Plenty of light is admitted through the open spaces between the 

 protecting timbers on top, thus allowing ready inspection and easy removal of 

 any debris lodging in the fishway. 



5. The cross partitions are set at a slight angle to the axis of the fishway, 

 and the floor of the fishway is slightly slanting, to bring the orifices in the lower 

 ends of the cross partitions and cause a current in the angles formed between 

 the cross partitions and the floor, thus automatically removing any accumu- 

 lation of sand, gravel, mud, and rubbish. 



6. The crest of the uppermost cross partition is at an elevation equal to 

 that of ordinary high water, so as to keep the water supply in the fishway nearly 

 the same at ordinary and high-water stage, avoiding thereby the need of any 

 regulating gates. 



7. The top and sides of the fishway are kept well above ordinary high 

 water, to prevent the flooding of the fishway and possible injury. 



8. Heavy timbers strongly bolted together are used in the construction of 

 the sides and top of the fishway when built of wood, with strong fender pieces 

 above the intake secured to the dam with heavy iron straps, to protect it against 

 drift ice and l9gs during freshets. 



9. Both the intake and the outlet are well submerged below mean water 

 level, and the intake is protected against floating debris, etc., by a substantial 

 iron grating. 



The necessary volume of water for supplying a fishway of the dimensions 

 as described here should not be less than 8 cubic feet per second. 



The construction of the fishway is alike adapted to wood, masonry, or 

 concrete, and it may follow either a straight line or have angles and returns, as 

 the local conditions may require. The construction is applicable to the various 

 forms of existing dams and natural waterfalls. The cost of construction of a 

 fishway built of timber as per illustration under ordinary conditions will be 

 about $1,000. 



Fishways of this design have proved quite efficient and have been built in 

 late years at various dams in the Susquehanna River and its tributaries; others, 

 built of concrete, were constructed at a number of the large electric-light and 

 power dams in several of the states. (See fig. 21, p. 1056-1057.) 



