108 OF THE DREDGE. 



tutting 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 C, 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. A C. This edge makes, with the 

 plane of the triangle, contained between the straight parts of 

 the two descending branches, A B, AC, 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 bodie? 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, B C, which may be seen in 

 fig. 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, b c, fig. 1. and 

 2., which crosses the triangle, ABC, 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, AC. 



The curvature of this rod removes it from the plane of the 

 triangle, b A c, in a 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 ; arid these removals in a contrary way, keep the bag 



