[3] A NEW SYSTEM OF FISHWAY-BUILDING. 45* 



some examples of such coustrnctiousmay be found in the United States^. 

 but I have uo iuformatiou of any. 



(U.) The inclined-plane fishway, as it is termed by Mr. Atkins, in which 

 the descent of the water is effected by a regultYr inclination of ihe floor 

 of the fishway, instead of by " steps " or " pools and falls." In order to 

 control the tendency to acceleration finder the action of gravity the base 

 of the incline is made very long in proportion to the height, and by a 

 series of alternating transverse or oblique partitions the water is con- 

 strained to follow a narrow, tortuous path with continual changes of 

 direction, the friction developed in its movement being sufficient ta 

 overcome the tendency to acceleration. Of this second general form 

 we have many examples in the United States, especially in Xew Eng- 

 land. The common rectangular fishway, the Brackett, the Foster,. 

 Pike's, Atkins', Swazey's, Brewer's, and Eogers' are examples of the 

 various designs that have been employed, each differing in minor details 

 of coTistruction, but all belonging to a common system. 



Most of these forms may be built either on an incline leading straight 

 down from the dam or with a return section so as to deliver the dis- 

 cbarge from the fishway close up to the foot of the dam, or they may 

 be built ill spiral form and boxed over so as to be made secure against 

 floods and ice. The fishway of Mr. J. D. Brewer is peculiar in the fact 

 that the channel to be followed by the fish is a zigzag groove excavated 

 or framed in the floor of the incline, which is built either of mason ly or 

 strong timbers ; the strength of the construction being such, it is pre- 

 sumed, as to prevent its destruction by floods or ice. The Rogers fish- 

 way is recessed into the dam and boxed over, the lower end discharging: 

 the water on a line with the face of the dam. This construction could,, 

 however, be aj)i)lied to any of the forms above indicated and has been 

 proposed in several of them. 



The experience of fishway builders in New England has shown that for 

 dams 10 feet in height or more it is not allowable to build the incline with 

 a rise of more than 1 foot in from 12 to 10, requiring a length of incline 

 of 140 feet for a 10-foot dam. The actual path, however, traveled by the 

 Avater and traversed by the fish ascending would be some two or three 

 times the length of the incline, so that fish passing up an inclined-plane 

 fishway rising 10 feet vertically, would necessarily travel a distance of 

 from forty to fifty times the height of the dam. For example, in the fish- 

 way over the Hadley Falls dam on the Connecticut Eiver,the total length 

 of the incline is about 1:50 feet. The distance to be travelled by the fish 

 ascending it is not far short of 1,500 feet, to overcome an ascent of about 

 29 feet. All the different designs of fishways constructed according to 

 the incline-plane system have, when judiciously located, proved more 

 or less successful in passing certain si)ecies of fish. In all, however^ 

 the labyrinthine route to be traversed, and the insignificant flow of 

 water through them, constitute very serious objections. 



