8 
houses is situated within the works, the water supply 
being obtained from a 20-ft. plank pond, used in winter 
as a settling tank, and whose feeder is supplied by a 
10-in. pipe from the main inlet works. These in their turn 
are supplied by a sluice in a coffer-dam, and guarded by 
a screen placed nearly parallel to the surface, formed of 
perforated zinc in summer and of wooden slats ? inch 
apart in winter. The wooden frame had been removed on 
the 3rd of March, when the temperature fell suddenly to 
12° Fah., and the thin ice floating down the surface of the 
stream clogged the perforated zinc screen, and froze into 
a solid mass, entirely stopping the supply of the works ; 
the water in the hatching trays unfortunately had been 
lowered two days before to increase the current so as to 
keep the eggs cleaner during the spate. The water fell in 
the boxes sufficiently to partially expose the eggs, these just 
showing the coloured globules which precede the formation 
of the red blood, and a thin film of ice formed on all the 
eggs. A few hours afterwards the screen was relieved, and 
the eggs thawed out by a gentle current of water. For a 
week no bad symptoms were visible, then several thousand 
turned white; in a month it was evident that, although 
few more eggs had actually died, most of them had made 
no further progress, and the few which showed a distinctly 
formed embryo only proved how thorough had been the 
work of destruction: the ice had squeezed all vitality out 
of my baby Trout. 
The stoppage of water by the screen being clogged with 
thin ice is frequently an invisible danger. It cannot occur 
when the stream is frozen entirely over, as the thin ice only 
travels on the surface, and when it comes against the screen 
is held there by the suction of the water in the same way in 
which a leaf is (this, of course, must not be confounded with 
