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 caleareous 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 emptyingit. 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. Ina 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 
