,1am. 10, 1884.] 



FOREST AND STREAM. 



479 



If we take a hemispherical bowl (fig. 1) and holding a marble 

 at A, upon the edge of the bowl, we release it. it will fall under 

 the influence of gravity through .41 to .42, coming to rest at 

 .42, some distance below the edge of the bowl. The vertical 

 distance between the positions .4 and A2, measures the force 

 of acceleration that has been counteracted bv friction by 

 traveling the constrained path A, Al, .42. 



If now, we take a number of similar bowls and cut them off 

 to the line .4 -42, and arrange them as in fig. ",, and start a 

 marble at D\, it will pass from Dl to 01, reaching Ol with no 

 greater velocity than that acquired in passing from .4 to .42. 

 If, however, the marble was allowed to roll unobstructed 

 from A to .41 down the incline plane D, C, (fig. 2) it will have 

 acquired a velocity equal to 8 > Db, approximately. 



We see, then, in this case how it is possible to deliver a 

 molecule from a given position to a definite lower position, 

 without the increase of velocity that would arise if the mole- 

 cule fell freely under the action of gravity or rolled down a 

 smooth incline. If it lie possible to compel everv molecule of 

 water descending through a fishway to submit to the condi- 

 tions above indicated, then the problem how to control the 

 velocity of a descending current would be solved. Now to 

 apply this to liquids, we arrange a series of bent tubes, shown 

 iu Fig. 4. By suitable arrangements we keep the longer 

 brauch of the higher tube of the series full of water. The 

 water escaping from each tube will rise against gravity until 

 it comes to rest then falls into the longer branch of the ad- 

 jacent tube m the series, and after passing through the entire 

 series be finally discharged from the shelter branch of the 

 lowest bent tube, with no greater velocity than it acquired iu 

 passing through the first member of the series. 



Construct a series of these tubes with branches brought 

 close together, cut away obliquely the upper end of the longer 

 branch of each member of the series, so as to permit access of 

 water, pack them side by side, in oblique position in an in- 

 clined sluice, as shown in Fig. 5, and we have the solution of 

 the problem with which we started. For if we suppose a 

 current of water to be running through the inclined trough or 

 sluiceway, the first effect will be to fill the tubes with water 

 and establish a How through them; the wsl ■. : firing tl 

 longer brauch of each tube will escape from the - 111 n i _t branch 

 with a velocity due to the head or vertical dial 



the two ends of the tube. This final direction being obliquely 

 up the slope, each particle of water will describe a path as is 

 indicated by the curved arrows shown in Fig. 5. The effect 

 will be that he will have an ascending current in the sluice- 

 on that side of the sluice where the shorter branches of the 

 tubes are situated. The velocity of this ascending current will 

 become, less and less as we pass toward the middle of the 

 sluice, where there will be a line or section of practically eddy 

 water, and beyond a descending current, becoming more 

 rapid as we pass to the further side of the sluice, where we 

 find a current descending with uniform velocity, the maximum 

 limit of which will be the velocity of the water escaping from 

 the shorter branches, provided the supply of water and the 

 capacity of the tubes are properly proportioned. The illus- 

 .trations here given present briefly 'and graphically the princi- 

 ples applied in the McDonald system of fishway building. 



The flexibility of the system adapts it to the widest range of 

 conditions occurring in practice. An effective passage maj r 

 be provided for the fish over the obstructions, with the supply 

 of water that will flow through a cross section six inches 

 square, or the fishwtrv may be expanded so as to take the en- 

 tire discharge of a river. Constructed roughly of boards, it 

 furnishes at a nominal cost the means of re-establishing our 

 innumerable trout streams to the natural conditions of repro- 

 duction. 



These fish-ways may be made so light as to be readily porta- 

 ble, so that, in the season when the fish are not running, they 

 may be stored away under -belter and thus protected from de- 

 cay or destruction by ice or floods. In public parks and trout 

 preserves, where considerations of cost are not controlling, the 

 fishway may be built of iron iu ornamental designs, and while 

 serving its essential purpose, made to contribute to the pic- 

 turesqueness of the landscape. Solidly built of stone and iron, 

 and of dimensions proportioned to the volume of the stream, 

 it may be made strong enough to resist the utmost force of 

 floods and ice, and by furnishing an easy passage for shad, 

 salmon, and other ananromous species of "fish, make possible 

 the restoration and maintenance of our valuable river fisheries, 

 in spite of the obstructions which are the inevitable and neces- 

 sary adjuncts of civilization. 



As un example of construction, we have Riven in Piy. Ha the 

 elevation, andin Fig. 68, the plan of a double fishway built of 



timbers. It consists of an inclined sluiceway of boards, the 

 sides and bottom of which are supported by suitable framing. 

 The sluice has in this case an inclination of one foot in three. 

 The upper end is let into the dam so that its upper line is flush 

 with the crest line of the dam. The lower end descends to 

 the water below the dam, and is firmly anchored by being 

 secured by bolts either to the rocky bed of the stream, or to 

 piles suitably placed, or by other suitable means. Intermedi- 

 ate supports may be provided, by trestling, as shown in the 

 figure, by log cribs or by rubble masonry. The incline flume 

 or sluice thus established furnishes the foundation for the 

 structure of the fishway proper which is placed within it. 



Details of construction are given in Figures 7, 8 and 9, which 

 are on a scale of one-fourth of an inch to the foot. The sub- 

 structure having been established, we begin by setting up 

 along the center fine of the trough or sluice, the bulkheads 

 /, I, I, and C, at intervals of twelve or fifteen inches. These 

 are made of planks one. and a half inches thick, two feet lon"- 

 and fifteen inches wide. These are firmly attached to the 

 flooring of the sluice either by spikes or bolts. Posts H, HI 

 and 0, of one and a half inch stuff, nine to twelve inches wide, 

 and extending from the floor to the upper edge of the inclined 

 trough, are now set up at similar intervals of twelve to fifteen 

 inches, and firmlv secured to the sides and bottom of the 

 trough. To the posts H. H, and bulkheads I, I, the fifteen 

 inch joists are securely nailed or bolted. The floor D, Fig. 8, 

 of one and a half inch plank is next laid and nailed to the in- 

 clined joists as shown in Figures T and 8, upon the floor D. 

 Next set up the short return buckets M. if. and C, Figures 8 

 and 9, securing the same to the parts H, H, and to the floor b\ 

 nailing or other suitable means. The cap E, E, Fig. 8, made 

 of a single two-inch plank is fastened securely to the sides 

 B, B, the posts H, H, and the return buckets M, M. thus com 

 pleting the construction. 



We have here realized in timber the same construction and 

 secured the same control of the descending current as shown 

 ifl the experimental apparatus, figure 5. " The course of the 

 water is show by the arrows. When a sufficient supply q 

 water is brought to the head of the fishwav, we will have a 

 average depth of water way above the 'floor, D, of ten 

 twelve inches. Any excess of water rat need 



to fill the fishway will be shed over the sides, and the fishw 

 wiil continue in effiej 



