46 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
galvanised iron one (WP), laid in a groove in the concrete 
floor, by which it is carried to the tipping box (TP). The 
dimensions of the tipping box are given in fig. 6. It 
is a wedge-shaped box made of wood 2 inch thick and 
coated inside with a mixture of tar and pitch. The 
bearings (BI) upon which it works are of ignum vite, 
and are screwed to the base of the frame which carries it. 
The bushes are of brass. At the back of the box is a 
small shelf, upon which rests a small box containing lead 
weights, and underneath the shelf a piece of wood 4 inches 
long projects in such a way as to touch the floor when 
the tipping box is full of water, and so give the initial 
move in tipping over. The side of the tipping box frame 
nearest to the first hatching tank has a piece of bar iron 
11 inches long and 1 inch wide projecting from it. This 
passes between the prongs of two guides, the outer of 
which is shown in figs. 8 and 6, TBG. The inner prong 
is smaller and is underneath the tank. The object of this 
is to keep the tipping box parallel with the side of the 
hatching tank when it is at work. 
The frame in which the box works is suspended by 
one end of a leneth of wire rope ;‘sths inch thick. This passes 
over a pulley of hard wood, 12 inches in diameter, which 
works in a frame of iron firmly bolted to the ceiling 
immediately above the box. It then passes over another 
pulley of the same size and under a third, to be finally 
secured to a ring in the ceiling. The frame in which the 
third pulley works is bolted to the short stem of what is 
called the balance beam (BB in fig. 6), a piece of 
wood 23 feet long, 44 inches wide x 1} inch thick. The 
ends of the beam are supported from the stem by 2-inch 
iron rods. From the balance beam the oscillating iron 
bars of the hatching tanks (OB) are suspended by means 
of brass wire. As a precaution, the upper end of the 
