60 FISH—CULTURAL ASSOCIATION. 
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 
discharge from the fish-way 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 fish-way of Mr. J. D. Brewer is peculiar in the fact, that 
the channel to be followed by the fish is a zig-zag groove exca- 
vated 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 presumed, as to prevent its destruction by 
floods or ice. The Roger's fish-way is recessed into the dam, 
aad 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 pro- 
posed in several of them. 
The experience of fish-way builders in New England has 
shown that for dams ten feet in height or more, it is not allow- 
able to build the incline with a rise of more than one foot in 
twelve to sixteen, requiring a length of incline of 140 feet fora 
ten-foot dam. The actual path, however, travelled 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 in- 
clined plane fish-way rising ten feet vertically, would necessarily 
travel a distance forty to fifty times the height of thé 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 1500 feet, to overcome an ascent of about 29 feet. 
All the different designs of fish-ways 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 labrynthine route to be traversed, and the insig- 
nificant flow of water through them, constitute very serious 
objections. 
AN IDEAL FISH-WAY. 
If it be possible, by any practical construction, to deliver the 
whole volume of a stream, over a dam or other obstruction with 
