[9] A NEW SYSTEM OF FISH WAY-BUILDING. 51 



arched culverts admit the water to a sluice which conducts it to the 

 head of the fishwaj'. This discharge of water is too far from the face 

 of the dam to secure the best results, and it will be necessary to erect 

 a deflecting wall at the lower end, to turn the current around the abut- 

 ment. This fishway has been in operation since the middle of May, 

 1883, and since the water has been turned on all the river species ex- 

 cept the shad have been observed j)assing in large numbers. Verj^ few 

 shad have reached the dam this season, the total catch by the nets being 

 less than two hundred. 



Fig. 12 shows plan of fishwaj^ on canal dam No. 4, on the Potomac 

 Eiver, near Shepherdstown, W. Ya. This was built in the winter of 1882, 

 stood witbout injury the heavy ice drifts and floods of the late winter, 

 and during the season just past has given full satisfaction to those 

 who have watched its operation. The black bass and other river species 

 have been observed to i^ass it in numbers and with ease. In this case 

 the fishway is sheltered behind the abutment on the Maryland side of 

 the river, the upper section being suspended to the abutment by stout 

 wrought-iron brackets. The water is conducted to the head of the fish- 

 way from the crest of dam by a trunk leading around the face of the 

 abutment. 



United States Fish Commission, 



Washington, D. C, August 25, 1883. 



explanation of the plates. 



Plate L 



Figure 1. Illustration of the combined influence of gravity and friction upon a 

 solid molecule while traversing a constrained path, the final direction being against 

 gravity. 



Figure 2. Illustration of the continual acceleration of a solid molecule rolling 

 down a smooth incline under the action of gravity. 



Figure 3. Illustration of the manner in which we may deliver a solid molecule 

 from a higher to a definite lower level without acceleration by application of the 

 principle developed in figure 1. 



Figure 4. Illustration of the same fact in regard to liquid molecules. 



Plate II. 



Fgure 5. Genesis of the fishway, showing how the jiriuciples developed in figures 

 1, 3, and 4 may be applied to deliver a curreut of water down a straight sluiceway, 

 with a velocity constant after the initial acceleration at the head of the sluiceway. 



Plate III. 



Figures 6a and 6&. General plan and elevation of the McDonald fishway. 



Plate IV. 



Figures 7, 8, and 9. Plan and sections of a double fishway to show details of con- 

 Atructjp;^, ^fif^le i-inch to 1 foot. This way is built of oak or other durable lumber. 



