212 COLLECTING SHELLS. 



means of the curvature, 6 B, c C, figs. 1 and 2, of tbe 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 tbe 

 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, 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 downwards, rakes the bottom 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, and 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, the use 

 of which will afterwards be explained. 



The upper part of the net is attached to a rod h c, figs. 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 extremities 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 Ac, 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, AC, at their 

 inferior extremities ; and these removals in a contrary way, 

 keep the bag always open, of which the edges have been 



