COLLECTING AND CLEANINC, SHELLS. 163 



to the Jower 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 

 bf 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 up})er part of the net is attached to a rod, h 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 

 rounds and nearly two inches in diameter ; the two extremities 

 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, 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; and these removals in a contrary way, keep the bag 

 always open, of which the edges have been attached, as we have 

 said, one end to the back plate, B C, and the other to the trans- 

 verse rod or bar, b c. 



This rod must be firmly fixed in its place ; for this purpose, 

 it is a little flattened, and pierced in its middle, D, with a hole. 

 A bar, A D, figs. 1. and 2., which comes from the summit, A, 

 of the dredge, and which is also flattened and pierced with a hole 

 at its extremity, D, is joined, by means of that extremity, to the 

 middle of the rod, b c, on the concave side, so that the two 

 holes are adapted to each other. The extremity of a small cross 

 bar of iron, Df, is made to pass these, which issues by the other 

 side of the rod, b c, and the bar, A D. The same cross piece of 

 iron, D f, is attached, in a similar manner, by its other ex- 

 tremity,^, which is made to pass, that it may be afterwards bent, 



