70 U. S. BUREAU OF FISHEEIES. 



Reinforcement for dam. 



Galvanized stock fence wire, 24-iuoli width preferred. 



Material for kettle. 



Walls 6 inches, bottom 6 inches ; total amount concrete, SO cubic feet. 



Cement bags__ 20 



Sand •_ ciibic feet__ 38 



Stone or gravel do 75 



1-2-4 mixture. 



aiODiriED FORM OF POND OUTLET. 



Figure 4 on page 71 shows a modified form of the outlet just de- 

 scribed, Figure 3. 



In this outlet terra-cotta pipe has been substituted for iron, and 

 the bell end of the terra-cotta ell, closed b}^ the wooden disk, re- 

 places the gate valve, while the cement dam, screen, removable 

 wooden dam boards, and other features remain the same. When 

 the pond is full, the ell opening is closed by the wooden disk, made 

 tight by the use of clay. The wooden dam boards need not be used 

 unless it is desired to raise the water level above the height of the 

 permanent cement dam. To drain the pond, the wooden dam boards 

 are fitted into their proper place and the wooden disk closing the 

 ell opening in the terra-cotta dam pipe is removed by means of the 

 iron rod to Avhich it is attached. The depth of water at any stage 

 of the operation may be controlled by proper manipulation of the 

 w^ooden dam boards. 



Each of the outlets described here, as well as the one described in 

 a previous ])ublication of the bureau,^ has distinctive points of ad- 

 vantage and have been developed in meeting the varied conditions 

 encountered in fishpond construction. It remains for the prospec- 

 tive pond builder to select the type best suited to his needs. The 

 types described here are considered particularly desirable in ponds 

 of comparatively large area or where the amount of water to be 

 carried requires the use of correspondingly large pipe. The con- 

 venience of the valve in controlling the flow of water in drawing 

 the pond. Figure 3, is easily recognized, but practically the same 

 results are obtainable with the simpler installation shown in Fig- 

 ure 4, and the cost of fittings for this type will be somewhat less. 



Work of Central Station, Washington, D. C. 



[L. G. IIarron, Superintendent.] 



Beginning with rainbow-trout eggs in December, 1920, and clos- 

 ing Avith pike-perch eggs in May, 1921, there were incubated in the 

 hatchery ai>paratus maintained in the fisheries building at Wash- 

 ington for ])ublic display 7,717.000 fish eggs, representing eight 

 species of fish — chinook salmon, rainbow and brook trouts, white- 

 fish, c-isco yellow perch, pike perch, and shad — from which 6,400,327 

 fry and fingerlings were distributed to applicants in Maryland, 

 A^irginia, West Virginia, Delaware, Penjisylvania, and New York. 



•"■ Cokor, R. E. : I'roprPRS in Biolojrical Innnirios, 1021. Report of the Oivision of Scien- 

 tific Inf|uirv for Ihe Fiscal Year Utlil. Appendix \III, Report, U. S. Commissioner of 

 Fislieries for 1921, 38 pp., 2 flgs. (A new Form of Pond Outlet, pp. 21-24, Figs. 1 and 2.) 

 Washington, 1922. 



