608 IMPREGNATION OF EGGS IN TROUT BREEDING. 
feet or even longer, and of any width from two feet to six 
or eight. If it is made very wide an additional longitud- 
inal support must be provided for the revolving screen. 
We recommend the following dimensions for speckled trout 
races: two feet wide and from ten to twenty feet long; or 
four fect wide and from twenty to forty feet long. The 
upper screens may be made in convenient sections, the whole 
width of the box, and six or eight feet long. 
The sereens F and D are so made that while a full current 
is permitted to flow over the upper screens (A), only a gen- 
tle current ean flow through the under part of the box. 
This current is meant to be so regulated that when the pan, 
C, is placed about an inch from the turning roller, all the 
small stones which the trout may whip through the upper 
screen will fall short of the pan; the eggs being lighter will 
be carried by the current into the pan, while a great part of 
the dirt, ete., which may collect on the under screen will be 
carried up over the pan and entirely out of the box. The 
revolving screen may be made of tarred muslin or some sim- 
ilar fabric. But wire cloth (of ten or twelve meshes to the 
inch) keeps much the cleanest and we are inclined to think 
it best for the purpose. I make my aprons, half wire cloth 
and half tarred muslin, furnishing the wire only with cross- 
bars and always leaving it uppermost. This apron is fast- 
ened around the rollers by a lacing of cord. At the end of 
the season the water in the pond can be drawn down a foot 
and everything taken out but the rollers. Give the screens 
a coat of paint or gas tar and lay them away in a dry place 
until the next autumn. A stiff brush may also be placed un- 
der the forward roller, so that every time tbe roller is turned 
to remove the eggs the screen will be perfectly cleaned. 
A few of the advantages of the plan are as follows: Let 
us compare a double row of forty Ainsworth screens, each 
two feet square and occupying a space in the raceway forty 
feet long and four feet wide, with one of the new spawning 
boxes of the same dimensions. 
