8 FISH PONDS ON FARMS. 
For a 1-acre pond, where the sides and bottom are of clay or rich 
loam, a flow of from 30 to 50 gallons per minute should be sufficient 
to maintain a proper water level at all times, while sandy or gravel 
.soil untreated may require double that amount. A practical method 
of measuring the flow of water from any source is as follows: 
Select a stretch on the stream or ditch affording as straight and 
uniform a course as possible. If the water at any point is carried 
in a flume, it will be better to measure at that point. Lay off a dis- 
tance of, say from 10 to 50 feet; measure the width of flowing water 
at about six different places in this distance, and obtain its average 
width. Likewise at these same points measure the depth of water at 
three or four places across the stream and obtain its average depth. 
Then drop a float in the water and note the number of seconds it 
takes to traverse the given distance. The product obtained by multi- 
plying the average width in feet by the average depth in feet by the 
velocity (expressed in number of feet per second) will give the flow 
of the stream in cubic feet per second. From the figures so obtained 
it is advisable to deduct about 20 per cent, as the surface velocity of 
water is in excess of the actual average velocity. 
High temperatures in season are necessary in brood and rearing 
ponds. If the water is cold at the source, the fault must be corrected 
by reducing the inflow to the lowest quantity that will maintain a 
uniform level, thus allowing the maximum absorption of warmth 
from the sun and air. Water that does not fall below 60° F. in the 
brood pond during the spawning season is desirable. 
SOURCES OF WATER SUPPLY FOR PONDS. 
Springs are the most dependable of all the sources of water sup- 
ply, requiring the minimum expenditure in preparation and being 
the least subject to outside influence. The presence of injurious min- 
eral substances can usually be detected without expert analysis, but 
the amateur fish-culturist may be surprised to learn that so-called 
pure water often carries abnormal proportions of oxygen or nitro- 
gen gases in quantities inimical to fish life. This may be due either 
to subaeration or superaeration, and the results following the use of 
such water will be as disastrous in the one case as in the other. 
This contingency and the requisite of high temperature make pre- 
carious the embodiment of springs and wells within the pond bed. 
In the absence of thoroughly demonstrated fitness, the more prudent 
course will be to provide an independent water supply reservoir, ap- 
portioning its area to the volume of the spring. While being held 
in this reservoir the gaseous contents of the water will be corrected ~ 
and its temperature seasonably modified. 
The flow from many springs is so obstructed through the trampling 
of stock or from other causes that they emit only a small portion of 
the water available near the surface. In such cases the supply may 
