348 THE PROPAGATION OF TROUT. 
duces naturally, with Seth Green's gigantic operations in growing Irout 
in it artificially, &c. 
To cultivate brook trout successfully, the water must be pure, clean 
spring water, free from all sediment ; but a tincture of lime, or sulphur, 
does no harm, as far as I have been able to discover in six years' obser- 
vation and practice. I have seen them hatch and flourish remarkably 
well in such water. 
The temperature of the water in the hatching races, or troughs, during 
the time of incubation must be between 36° and 48° to insure success. 
The best temperature, in my opinion, all things considered, is from 42° 
to 45°. When above this temperature they hatch too soon, and are too 
weak and tender. When below, more or less die during incubation. 
Consequently great care should be taken to place the hatching boxes for 
artificial propagation, or to make the spawning beds in natural cultiva- 
tion, where the water will ' be within these temperatures during the 
coldest weather in winter. The temperature of our best springs is 48° 
the year round. 
• Trout will not do well where the water rises in the summer above 
60° or 64° at most. The best temperature to grow them to perfection 
is between 50° and 58° 
This fact should always be born in mind when constructing ponds, 
so as to have the size of the ponds correspond with the volume of water 
in the stream supplying them. 
For example, a spring that produces as much water as will run 
through an inch square hole, will supply a pond 20 by 30 feet 
square, or 600 square feet surface, and keep the water below 64° through 
the summer, and if covered with a house, or boards, so as to shade the 
water effectually, it may be double this size. I have one of this size 
shaded, supplied with an inch stream, the temperature never rises above 
64°, and the trout are always perfectly healthy in it. 
When the spring or stream will fill a four inch square hole, then the 
pond may be sixteen times as large, containing 9,600 square feet, or a 
pond 80 by 120 feet square, and so on, according to the size of the 
stream. 
For growing large trout, the water should be from 8 to 15 feet deep; 
for small ones, from 2 inches to 5 feet, according to the size of the trout. 
An inch stream running through two perfectly arranged hatching 
troughs, will hatch 200,000 spawn, and grow them till about 1^ inches 
long, when a part of them, from time to time, must be put into other 
streams. This stream will grow 10,000 trout the first year, 2,000 the 
second year, and 500 the third year, thus decreasing rapidly in num- 
ber as they increase in size. 
A 16-inch stream might hatch 3,200,000 trout ; grow 160,000 the 
first year, 32,000 the second year, and 8,000 the third year, and 3,000, or 
4,000 the fourth year that would average one pound each. 
Young trout, till from 1 to 2 inches long, do much the best in 
