424 Birge — Vertical Distribution of Pelagic Crustacea. 
the weights for moving the cover, and the attachment for the 
net. 
The frame is 44 cm. long by 23 cm. wide on the outside, 
42 cm. by 20 cm. inside. It is made of brass tubing 1 inch 
square and 1-32 of an inch thick, split longitudinally so as to 
leave one flange — the top one — f of an inch wide, and the 
other § of an inch wide. ( A , PI. VIII, fig. 1.) The pieces are firmly 
soldered together so that the flanges project outward. At the 
corners are fastened ears, pierced for the four cords by which 
the frame is hung to the dredge line. A half-piece of tubing 
similar to that of the frame is soldered across the frame near 
the middle, so as to leave an opening at one end 20 cm. square. 
Beneath this opening is fastened the net, and this end is called 
the front of the frame. 
To the top flange on the sides of the frame aud across the 
front end is soldered a strip of sheet brass 1-32 of an inch 
thick, and about \ of an inch wide. ( B ) This is attached 
close to the outside of the upper flange. Above it is fastened a 
strip of thin spring brass — the guide (67) — of the full width 
of the top flange, leaving between it and the flange a deep 
narrow cleft open toward the inside of the frame. In this 
groove the cover slides. Jn the middle of each end of the frame 
is attached a pulley (E), over which pass the cords for moving 
the cover. Just above the front pulley is an eye of wire (67), 
through which passes the cord to the cover. Its purpose will 
be mentioned later. 
The cover is a flat piece of thin spring brass. The sides and 
front edge are not modified at all. The rear edge is bent over, 
so that when closed the cover fits closely over the flange of the 
partition in the middle of the frame. Around the front and 
sides of the cover is soldered a strip of thin sheet copper 
of an inch thick, and of an inch wide. ( E ) The inner edge 
of this strip is folded on itself, and attached to the cover so 
that the free edge is parallel with that of the cover, leaving be¬ 
tween it and the cover a deep, narrow groove, in which fits 
the guide of the frame. On the top of the cover are soldered 
two eyes ( J) for the attachment of the weight cords. In a 
-dredge which is to be worked from a large boat it is well to 
