MARINE BIOLOGICAL STATION AT PORT ERIN. AT 
frame of the pulley attached to the balance beam is 
secured to the ceiling by means of a short length of rope, 
so that in case of breakage of the wire rope the beam 
would still remain suspended (see fig. 6). 
When the apparatus is in action, the water which 
has passed through the hatching tanks into the waste 
pipe (WP) is poured into the tipping box. As the latter 
fills, its weight gradually lowers the box and so raises 
the balance beam and the suspended oscillating iron bars, 
and the floating boxes in the compartments of the 
hatching tanks rise by their own buoyancy as they are 
released from the weight of the bars. When the tipping 
box is nearly full (the precise moment is regulated by 
the weights in the small box at the back) it tips over and 
empties its contents into the circular depression in the 
concrete floor, from which the water escapes by means of 
the gutter to the drain outside the building (see ground 
plan). The moment the tipping box is empty the weight 
of the balance beam and the suspended oscillating bars 
comes into play, and the former falls until the latter he 
parallel with the longitudinal partitions of the tanks and 
so depress the hatching boxes by means of the short 
transverse iron rods. The tipping box fills and empties 
about four times in five minutes. 
When the hatching boxes (see figs. 3 and 4) 
are depressed in the compartments of the tanks, the 
sea-water is forced upwards through the meshes of 
the bolting silk, so as to cause ascending currents which 
keep the fish eggs or embryos suspended in the water and 
prevent them from accumulating on the bottom or 
stagnating on the surface. This mechanical device for 
giving an intermittent vertical motion to the water in 
the hatching boxes—apart from the gentle horizontal 
flow from compartment to compartment—is actuated 
