108 OF THE DREDGE. 
cutting edge in front, turned upwards, at an angle of about 
sixty degrees. The back, or that part opposed to the edge of 
the plate, is an inch thick. By means of the curvature, b B, 
c CG, fig. 1. and 2., of the two lateral branches, A B and A C, 
the edge of the plate, B C, is brought forward, and a little 
turned to the side of the summit, A, as may be seen in the 
profile of the dredge, fig. 2. AC. This edge makes, withthe | 
plane of the triangle, contained between the straight parts of | 
the two descending branches, A B, A C, an angle of about 
sixty degrees. 
There is a large iron ring attached to the summit A ; when, 
by means of a rope passed through this ring, the dredge is 
dragged along the bottom of the sea, the edge, B C, which is | 
turned to the lower side, next the bottom, rakes it strongly, 
and detaches from it all the bodies which adhere to it: but it 
is not enough that these bodies should be detached from the 
bottom of the ocean ; they must also be retained, and raised by 
means of a net. 
This net, attached to the dredge, and which follows it at the 
bottom of the sea, in order that it may receive within it the | 
bodies that are detached, has the form of a bag. The lower 
part of this bag, which is intended to drag along the bottom, 
should be made of untanned hide, so as to resist the friction. 
The side next the plate should consist of straps of leather, 
crossing each other like a net; which are attached to eight 
holes in the back of the plate, BC, which may be seen in 
fir. 1. This plate is pierced with eleven holes, but three of 
them are intended for the reception of three bars, whose use 
will afterwards be explained. 
The upper part of the net is attached to a rod, 6, fig. 1. and 
2., which crosses the triangle, A BC, parallel to the plate 
B C, which is distant from that plate about two feet: this rod 
is round, and nearly two inches in diameter ; the two extre- 
mities terminate in a flattened end, perforated to receive the 
two ascending branches, A B, A C. 
The curvature of this rod removes it from the plane of the 
triangle, 5 Ac, ina way contrary to that in which the base of 
the plate, B C, is removed from it, by means of the curvature 
of the two ascending branches, A B, A C, at their inferior ex- 
tremities ; and these removals in a contrary way, keep the bag 
