70 U. S. BUREAU OF FISHERIES. 
Reinforcement for dam. 
Galvanized stock fence wire, 24-inch width preferred. 
Material for kettle. 
Walls 6 inches, bottom 6 inches; total amount concrete, 80 cubic feet. 
Cement______ ad kOe 19 spags 29 +20 
Sendiond anit cp yep ecubie feet__ 38 | 1-2-4 mixture. 
Stone‘or gravel. = -_._=_- doe 86 . M5 
MODIFIED 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 by 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 which it is attached. ‘The depth of water at any stage 
of the operation may be controlled by proper manipulation of the 
wooden dam boards. 
Each of the outlets described here, as well as the one described in 
a previous publication 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. Harron, Superintendent. ] 
Beginning with rainbow-trout eggs in December, 1920, and clos- 
ing with pike-perch eggs in May, 1921, there were incubated in the 
hatchery apparatus maintained in the fisheries building at Wash- 
ington for public display 7,717,000 fish eggs, representing eight 
species of fish—chinook salmon, rainbow and brook trouts, white- 
fish, cisco yellow perch, pike perch, and shad—from which 6,400,827 
fry and fingerlings were distributed to applicants in Maryland, 
Virginia, West Virginia, Delaware, Pennsylvania, and New York. 
3 Coker, R. E.: Progress in Biological Inquiries, 1921. Report of the Division of Scien- 
tifie Inquiry for the Fiscal Year 1921. Appendix VIII, Report, U. S. Commissioner of 
Iisheries for 1921, 38 pp., 2 figs. (A new Form of Pond Outlet, pp. 21—24, Figs. 1 and 2.) 
Washington, 1922. 
