Flow to obtain itt. 61 
is too cold or barren, and will not grow trout at all, whereas, the 
same water supplying a second pond will do very well for the 
purpose. The fact is, that it simply requires a little cultivation to 
render it fit for use. After being exposed to the air and the rays 
of the sun in the spring pond, which contains also some vegetable 
life, it becomes changed in its nature, and in passing out of this 
pond and along a raceway, even though the latter be only a few 
yards in length, it becomes still further changed. This applies 
more or less to a great many springs. The water often becomes 
so rapidly changed that trout will thrive even in a spring pond. 
I have had cases in which they have done well in ponds that 
had neither visible inlet nor overflow. Being fed by springs the 
water would rise to a certain level, when, owing to the nature of 
the soil, the absorption was so great that it could rise no higher. 
There was, in fact, a stream flowing through the pond, and a pond 
of this nature may be an excellent place for trout. 
Water readily takes up oxygen, and the more rapidly this 
combination is brought about the sooner does it become suitable 
for maintaining them. Whilst receiving a supply of oxygen it 
also precipitates substances held in solution, and thus it will be 
seen that the water flowing out of a pond may essentially differ 
from the water flowing into it, if it be from springs. Plants give 
off oxygen, and, as a rule, in other ways tend to render it more 
suitable for fish. It is a well-known fact that even impure water 
as in the case of a stream, becomes purified as it pursues its 
course. Exposure to the air and the absorbing power of the 
earth and other causes are at work to bring about this change. 
Where the water supply is obtained frém springs, therefore, it is 
desirable to pass it through a preparatory pond if practicable, and 
it is important that this pond should contain vegetation of a 
proper kind, as the plants not only give off oxygen but produce 
favourable conditions for a crop of natural fish food. So much, 
then, for ponds with a limited water supply. 
Where a good supply is at hand I would say secure it by all 
means. A stream that will fill a twelve-inch pipe will keep a 
good series of trout ponds going. If double the supply can be 
obtained at times so much the better. Although it is not only 
desirable, but necessary, in the case of a successful trout pond, to 
