How to obtain it. 67 
then lasts much longer. Perforated iron plates do very: well, and 
are of course more permanent. They require no frames, and are 
quite easily fixed. An ordinary iron grating is also excellent, but 
it must be borne in mind that a fish can readily pass between two 
bars of metal which could not possibly pass through a round hole 
of the same diameter. The bars may be a quarter of an inch or 
they may be half an inch apart, but the greater the width between 
them the more readily will fish pass through and escape. It 
may be argued that fish do not go down stream out of ponds. 
I know many ponds where there is no outlet screen, and where it 
has been supposed there is no need for one. This is a mistake, 
however, and I have met with instances in which fish have been 
lost in considerable numbers owing to it. At times, and under 
certain circumstances, they will and do go down stream if not 
prevented. There are some instances, however, in which a large 
number of fish may run up stream into a pond, and of course all 
things have to be taken into account, and each particular case 
treated according to circumstances. One thing I am quite sure 
of, and that is, that every fish pond that has been specially made 
and stocked with fish, and that has a regulated supply of water, 
ought to have an outlet screen. 
Having decided upon the material that is to be used, the 
next thing is to consider the more important points that are to be 
observed in the fixing of a screen. We must first be sure that it 
is capable of passing all the water during rainy weather. This is 
in itself a very simple consideration, and in the case of a well 
made pond that is not subject to flooding, is easily calculated. 
By having a screen that will pass double the quantity ‘of water that 
can by any possibility flow from the pond, it should be fairly safe. 
Of course, the amount of floating matter that is liable to be 
driven on to it must be well considered and allowed for, and it is 
better to have the screen twice as large as is necessary than to 
have it just a little too small. One double the capacity required 
is, under ordinary circumstances, usually large enough. 
There are so many old ponds in use that are liable to have 
floods tearing through them, that I will just give a hint or two 
concerning them. The chief point in their case is to have the 
screen large enough. Make it as big as you like, but do not on 
