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



some examples of such coustructions may be found in the United States^ 

 but I have no iDformation of any. 



(L'.) The inclined-plane fishway, as it is termed by Mv. Atkins, in which 

 the descent of the water is effected by a regular inclinaticn of ihe floor 

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

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

 of the incline is made very long in i)roportiou 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 to 

 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 Sogers' are examples of the 

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

 of construction, 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 w ith a return section so as to deliver the dis- 

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

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

 floods and ice. The fishway of Mr. J. D. Brewer is j^eculiar 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 masonry 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 applied 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 16, requiring a length of incline 

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

 water 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 River, the total length 

 of the incline is about 450 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 species of fish. In all, however, 

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

 water through them, constitute very serious objections. 



