ATKINS ON FISH- WAYS. 595 



pools farther down, but ou starting afresh the chances are that they 

 will again follow the main current, to be again baiiled by the insnrmount- 

 able fall. In this way they will repeatedly pass the month of a fish-way 

 that opens into the main stream at some distance below the obstruction 

 without noticing it, being attracted by the superior volume of the main 

 river, while one whose entrance is in close proximity to the fall will soon 

 be discovered. 



The mode of securing an accessible location is sufficiently simple. It 

 has been the general practice heretofore, in building ways for salmon 

 and alewives, to place the upper end at the crest of the dam, or very 

 near it. If the height to be overcome is very small, only a short fish-way 

 isrcqnired, and it can generally bebniltfor its whole length straightdown 

 the river, without carrying its lower end too far from the dam. But if 

 a great length is required, the simplest way of avoiding difficulty is to 

 turn the lower part of the fish-way at whatever angle may be required — 

 even directly reversing it in many cases — and bring the lower end back 

 to the vicinity of the dam. Tbus, if the fish-way must be 350 feet long, 

 it may be carried from its upper end 200 feet down stream and then 

 brought back 150 feet, so that it will discharge its waters 50 feet from 

 the dam. These reversed fish-ways have been built in many places, 

 and this may be considered the most eligible form of Smith's, Foster's, 

 and similar devices. In Pike's and Gail's spiral fish- ways, the same end 

 is sought and attained by keeping the whole structure within a few feet 

 of the dam, so that, on whichever side the water is discharged, itw ill 

 always be sufficiently near the dam. In some cases it is practicable to 

 place the upper end of the fish-way in a canal at such a distance below 

 the dam that it may slope directly toward the latter and end near it. 

 Such a location has been adopted in plans recently devised for a fish-way 

 at Augusta, on the Kennebec. In devising a way for shad through the 

 dam at Columbia, ou the Susquehanna, the Pennsjdvania commissioners 

 deemed it essential that the foot of the fish way should be no farther 

 down the stream than the face of the dam, so that in searcliiug for its 

 entrance the shad should not be compelled to fall back at all, but should 

 find it as a gap in the dam itself, in and above which the whole body of 

 the fish- way was placed. So far as accessibility is concerned, such a 

 location is perfect. 



A fish- way may with propriety be located at either end of a dam which 

 is built straight across the river and at right angles with its course? 

 other things being equal ; but it is always desirable to have it nearer to 

 the strongest current and the main channel of approach. This deside- 

 ratum cannot, however, always be secured; considerations of conven- 

 ience and safety oftener dictating the location. 



If the dam crosses the river obliquelj^, the best location is generally at 

 the upper end, toward which the fish naturally tend as soon as they en- 

 counter the obstruction. This is illustrated by the success of the fish- 

 way at Warren, on the Saint George, where both the obliquity of the 



