12 ARTIFICIAL. PROPAGATION OF PACIFIC SALMONS. 



is longer than the other two, which are of equal dimensions, and is 

 attached to them at an angle of 90°, the spread between the others 

 being about 60°. The legs are braced and held in place by poles 

 about 4 inches in diameter, which are spiked to the sides midway 

 from the ground to where the legs are joined, and, as an extra pre- 

 caution, an additional brace is nailed across the two rear legs. 



The braces strengthen the bottom of the crib, which is made of 

 1-inch rough lumber, and the 12-inch boards composing its sides 

 serve as an additional brace to the legs. Such a crib will hold from 

 100 pounds to almost a ton of rock, the amount varying with the 

 size of the braces used and the current which it is expected to with- 

 stand. 



The trestles are set from 8 to 12 feet apart directly across the 

 stream on the site selected for the rack, the distance between each 

 being governed by the size of the stream and the strength of rack 

 desired. The trestles are then lined up and loaded with stones, and 

 two stringers from 8 to 12 inches in diameter are put on and spiked 

 to the upstream side of the forward leg. While the position of the 

 stringers must be governed to some extent by the height of the rack, 

 it is usual where the rack is of ordinary construction to place the 

 upper stringer about 30 inches above the water surface and the 

 lower one midway between that point and the river bottom. On 

 large streams a third stringer is sometime* used to good advantage. 



Where the bed of the stream is of hard formation 2 by 3 fir pickets 

 are put down even with the bottom at intervals of 1^ inches and 

 nailed to the stringers, the 2-inch surface being placed to the current 

 and the upstream edge beveled in order to present the least possible 

 resistance to the current. In streams with soft shifting bottoms it 

 is often necessary to drive the pickets. As a further precaution 

 against the escape of the salmon by the loosening and displacement 

 or the pickets by the current, or by the struggling of the fish, a 

 block 3 inches long by 1^ inches wide is nailed to each picket at a 

 point halfway between the lower stringer and the bottom. A layer 

 of bowlders and rock from 3 to 5 inches in diameter is then placed 

 in fi'ont of the rack at the point of the pickets to close effectually all 

 openings between the ends of the pickets and the river bottom ; and 

 brackets for supporting a walk are nailed to the downstream side 

 of the trestles, thus providing a means of keeping the rack cleared of 

 debris at all times. , 



In streams where shingle bolts, cordwood, and driftwood occur, a 

 gate is provided for their passage, and the necessary sheer booms are 

 constructed in front of the racks to guide the tinibers to the opening. 

 The gate should be built between two trestles which have been placed 

 8 feet apart, and the open space connected by a stringer placed below 

 the surface of the water at a depth of at least 18 inches. Pickets are 

 attached to this stringer in the usual manner, except that they must 

 be sawed off even with its top, and the sides of the space are squared 

 up and walled with 1-inch lumber. 



The gate is constructed of 1 by 4 inch strips 12 or more feet long, 

 which are placed on edge at intervals of 1| inches, well blocked and 

 braced. It is then hinged to the stringers in such a manner that it 

 will swing freely. One way to accomplish this is to bore holes 

 through the encls of the strips and insert 1-inch pipe, the ends of 

 which, projecting a few inches on either side of the gate, allow it to 



