HEARING. 53 



the water, the aspect of the place where the boxes are 

 situated, the convenience of the rearer, and many 

 other considerations ; therefore no hard-and-fast rule 

 can be laid down ; but it may safely be stated that 

 when the water approaches 60 F. out they should go; 

 and all needful preparations should have been made 

 some time beforehand, so that any defects may be 

 discovered and corrected before the breeder turns his 

 precious infants into a new sphere of life. 



Before, however, an open stream is used for fry, 

 all the weeds and mud should be removed and the 

 height of the water carefully noted, as weeds have a 

 great tendency to heap the water up and give it an 

 artificial height which is immensely above the natural 

 level when cleared out effectually. The writer, at the 

 moment of writing this, has but just returned from 

 visiting a stream of this sort, which, instead of hold- 

 ing a foot or more of water, has not more than three 

 inches of depth, and in a dry season would require 

 to be dammed up by artificial means. 



If a few little falls can, under any circumstances, 

 be made in the stream, they will be advantageous to 

 the fry, as they like strong, rippling water ; these falls 

 also tend to oxidize the water by exposing it in thin 

 films to the air, and have a neutralizing effect on any 

 impurity that may by any chance find its way in. 

 Water plants have this effect also, and should, there- 

 fore, be encouraged to a moderate extent, especially 

 as they also act as shelters or hides. 



The woodwork required for the screens at each end 

 of the water consists of a "sole-plate," a good solid 

 slab of timber some six feet longer than the width of 

 the stream, having two strong uprights mortised into 



