446 SALMON AND TROUT. 



sometimes an interval of as much as three months between the 

 first and last ova obtained, a second crop is laid down, and the 

 boxes or troughs are used over again. 



The troughs now in general use in my hatchery are made 

 of wood. They are three feet long, by one foot wide, and six 

 inches deep, and supplied with water through a punctured pipe 

 running all round the trough. They are fitted with movable 

 perforated zinc trays twelve inches (bare) by six inches wide and 

 three inches deep. This plan, although not entirely a novelty, 

 appears to have simultaneously suggested itself both to myself 

 and to Mr. Oldham Chambers, whose practical experience in 

 fish culture generally is well known. It seems to have ori- 

 ginated in my very old plan of using perforated zinc trays, into 

 which were counted the ' Fry ' previous to sending away. The 

 ova it was imagined were placed in these trays, which were put 

 on the bottom of the overflow trough, but of course the eggs 

 perished as the water did not circulate. It was then thought 

 that such trays would answer for hatching ova if raised from 

 the bottom of the trough, and the water made to circulate by 

 an upward current. This plan, though not claimed as an inven- 

 tion, can hardly be called a modification of any other, although 

 it bears some resemblance to several which have been used in 

 America. It has certainly found favour among pisciculturists 

 on account of its great economy in the items of prime cost and 

 of space. One of these troughs costs about 55$. complete, and 

 will bring on over 100,000 eggs, whilst a set of six slate troughs 

 costs between 8/. and gl. and will not contain more than half 

 the number of ova. The trays may be much larger, but I 

 prefer this size on account of their handiness and comparatively 

 slight weight. Instead of * carbonising ' the wooden troughs, I 

 have them coated, as well as the zinc trays, with tar varnish. 

 Silicate paint answers as well. 



Livingston Stone, in the book before referred to, says, * One 

 form or the other of the tray system is undoubtedly destined to 

 entirely supersede the old methods of hatching on glass grilles 

 or on the bottom of troughs.' 



