PREFACE. xl 
which will, of course, depend on the depth at which it is to 
be used; for anything under 40 fathoms ths in. is suffici- 
ently strong, the length required being about one-half more 
than the depth of water. A nest of copper wire sieves is 
also necessary for washing the material obtained; these may 
be 4 in., $ in., and zy in. in the mesh, and about 14 in., 15 in., 
and 16 in. respectively in diameter. The frames should 
be of oak, or other wood which does not swell. Jars, bottles, 
and boxes may be added to the outfit, as may be thought 
desirable. A very old suit of clothes is de rigewr. 
When a haul has been made, the dredge should be care- 
fully emptied upon the board, and the material transferred in 
convenient quantities to the sieves, and washed in sea water 
either over the side, or if the boat is large enough, in a tub 
on board. The coarse material in the upper sieve may be 
examined and dismissed on the spot, whilst the finer stuff in 
the lower sieves should, after a cursory search for living 
specimens, be put into bags, labelled, and taken home for 
more leisurely examination. The finest material, which 
often contains the rarest specimens, should, when thoroughly 
dried, be placed spoonful by spoonful on a black japanned 
tray, and carefully turned over, grain by grain, with a 
camel hair pencil, an ordinary pocket lens being at hand 
for determining anything doubtful. This laborious exam- 
ination is, I think, the béte noire of the dredger, but no 
more rapid method is possible—patience and enthusiasm 
will carry one through bushels of this residuum. All 
marine shells should be soaked for some time in fresh 
water before being packed up or placed in the cabinet, but 
care must be taken not to allow fragile species, or such as 
have a very delicate epidermis, to remain more than a few 
hours in fresh water, otherwise they may receive consider- 
able damage. 
As a general rule, when the water is deeper than four or 
five fathoms the dredge should not be dragged against the 
tide, as the current tends to lift it off the bottom and so 
prevents the scraper working properly. In stormy weather 
the naturalist will do well to devote himself to the littoral 
