DEEP-SEA EXPLORATION. 
3G3 
BOAT DREDGE. 
The boat drodge is essentially a ininiatiD'e form of tlie ordinary ship’s dredge 
already described, and is designed for use from boats where it must be worked by 
hand. Its dimensions are as follows: 
Jaws : Lengtli, 1 foot 7 inches ; width, 
inches; opening, 71 inches; angle, 12 
degrees. 
Stnd : Length, 6.1 inches ; diameter, round 
iron, f inch. 
Bridle: l>iameter, round iron, 1 inch; 
length, 1 foot 5 inches. 
Weight, 15 pounds. 
Net: Length, 1 foot 8 inches; sis!e of 
mesh, sipi are, inch ; material, cot- 
ton, 3-thread, hottom donhlc. 
Shield : Length, 2 feet 8 inches ; material. 
No. 3 cotton canvas. 
THE OYSTER DREDGE. 
The oyster dredge is of tlie ordi- 
nary commercial i)attern used in 
Chesapeake Bay. The rake is a flat 
bar of iron G feet in length with num- 
erous projecting teeth. The bag is 
comiiosed of a network of wire links 
and has a capacity of about 15 
bushels. The dredge mouth is kept 
open by an iron frame. This dredge 
is used solely for the collection of 
mollusca. 
THE TANGLES. 
The present form of tangles (plate 
xxxiii) was devised by the ivriter in 
1881 and they have since been used 
on board the Alhafrons for collecting 
on rocky bottoms, coral reefs, and 
other foul grottnd, capturing a great 
variety of specimens where no other 
appliance can be made available. 
The bow a is made of spring-tempered steel and permits the bars to close with a 
pressure of between 300 and 400 pounds applied to their extremities, so that the 
api>aratus will pass between rocks or other obstructions which permit the ]tassage of 
the bow and sinker. 
Each tangle is secured to its bar by a inch eyebolt, which draws at a tension 
of about 1,000 ])ounds, releasing its tangle when irretrievably fouled on the bottom 
without endangering the loss of the whole apparatus. The tangle bars are made 
separate from the bow and attached by bolts and nuts at e to secure better stowage 
and make the parts lighter to handle, Tiie semicircnlar arm /is intended to raise the 
forward end of the tangle frame a few inches off the bottom; also to act as a shoe in 
Cut 67. — The Blake dredge. 
