CHAP, vi.] DEEP-SEA DREDGING. 259 



the bag is about half full. If, from a great depth, 

 beyond the reach of currents, where there is only so 

 slow a movement of the mass of water that the finest 

 sediment is not carried away, it contains usually 

 fine calcareous or aluminous mud alone, with the 

 animals forming the fauna of the locality distributed 

 through it. In shallower water we may have sand 

 or gravel, or stones of various sizes mixed with mud 

 and sand. 



The next step is to examine the contents of the 

 dredge carefully, and to store the objects of search for 

 future use. The dredge is hauled on deck, and there 

 are two ways of emptying it. We may either turn it 

 up and pour out its contents by the mouth, or we 

 may have a contrivance by which the bottom of the 

 bag may be made to unlace. The first plan is the 

 simplest and the one most usually adopted. The 

 second has the advantage of letting the mass out 

 more smoothly and easily, but the lacing introduces 

 rather a damaging complication, as it is apt to 

 loosen or give way. In a regularly organized dredg- 

 ing expedition, a frame is often arranged with a 

 ledge round it to receive the contents of the dredge, 

 but it does very well to capsize it on an old piece of 

 tarpauling. Any objects visible on the surface of 

 the heap are now carefully removed and placed for 

 identification in jars or tubs of sea- water, of which 

 there should be a number standing ready. The 

 heap should not be much disturbed, for the delicate 

 objects contained in it have already been unavoid- 

 ably subjected to a good deal of rough usage, and 

 the less friction among the stones the better. 



Close to the place where the dredge is emptied 



s 2 



