ATKIXS ON FISHWAYS. 611 



The large size of these fish-ways is deiuanded by the peculiar character 

 of the shad, for the use of which they are designed. They are of too 

 costly a character to be used ou high dams, eveu if it were possible to 

 conduct a body of water down a long open plane like this without the 

 attainment of too great velocity. The tish-way of 18(36 may have given 

 passage to some shad, bat has not met the expectations of its builders. 

 That of 1873 has had one season's trial without fully establishing the 

 fact of its success. 



11. — THE CO:\niON RECTANGULAR FISHAVAY. 



This (Plate XXXI, in operation) is apparently the original style of the 

 inclined-plane fish-way. The partitions are run at right angles with the 

 sides of the fish-way, making rectangular compartments, (commonly 

 square,) with passage-ways one-eighth or one-fourth the width of the 

 fish-way, cut quite down to the tioor, and placed alternately against the 

 right and the left side. This is very closely like Smith's in form and 

 action, being in the latter respect almost identical when well supplied 

 with water. In case of a scanty supplj- of water, the advantage is with 

 the inclined plane, particularlj- for such fish as alewives. This device 

 w.as in common use in the eastern part of Maine for many years previous 

 to Mr. Foster's improvements, which were made about 20 years ago, and 

 is probably of as early origin as Smith's. When well proportioned and 

 located, it is very successful with both salmon and alewives. Among the 

 various modifications introduced, the following deserve notice : 



First, to avoid the violent swirling of the water, which takes place 

 when the floor is an interrupted plane, the bottom of each passageway 

 is blocked up a certain distance above the floor, resulting in an increase 

 of the depth of water in the compartments without increasing the vol- 

 ume flowing, and making a perpendicular fall at each passage-way. In 

 the latter result lies the only disadvantage, and this can be overcome by 

 placing against the lower side of the blocking an inclined plane, which 

 shall support the descending body of water. It should be remarked that 

 the blocking of the passage-ways turns the structure into a step-fish-way, 

 and that the same mode of overcoming the difficulty of the perpendicular 

 fall may be applied to any step-fish- way. 



Secondly, to check the force of the water across the pool, and thereby 

 prevent a difficult cross-current in the j)assage-way, an arm is attached 

 to the upper side of each partition -wall and at right angles with it. 

 This modification has been many years in use at Warren ou the Saint 

 George Eiver. 



Thirdly, to avoid the large eddies and accompanying waste of space 

 caused by the large compartments, the partitions are placed nearer to- 

 gether. When the distance between the partitions is equal to the width 

 of the passage-ways, the latter being, say, one-third or one-fourth the width 

 of the fish-way, eddies are almost wholly avoided, and the economy of 

 space is so great that a grade much steeper than ordinary can be adopted. 

 A combination of this and the first modification is stronglv recommended. 



