Juday—Limnological Apparatus. 
579 
water. A hole in the top door similarly protected, permits 
the air to enter the trap when it is hauled out of the water. 
The release consists of two long pieces of brass tubing which 
are connected at the top by two shorter pieces of tubing. 
(See fig. 5.) The upper cross piece bears a small brass frame¬ 
work which is movable, backward and forward, as well as 
1° , t 
1. " 7!H 
Fig. 5.—Release of plankton trap. 
sidewise. The line supporting the trap passes through a 
hole in the upper piece of this small framework and is tied 
below to the two ropes which are attached to the four cor¬ 
ners of the trap. Thus this cross piece receives the im¬ 
pact of the messenger. The two long pieces of tubing 
extend down on both sides through holes in the side pieces 
of the upper and lower framework. A clamp at the lower 
end holds them in place. They are supported at the bottom 
by two coil-springs which surround the tubes and rest in 
