MANUAL OF NATURAL HISTORY. 657 



arrived at the fishing-ground, ascertain the depth of 

 the water and the nature of the bottom with a 

 sounding lead ; register these data, which are of the 

 greatest importance, in a pocket journal; drop 

 the dredge overboard, allowing one-third more line 

 than the ascertained depth, and drag the dredge 

 along by sailing or rowing ; when full, let it be 

 draped into the boat. Let the Nudibranchiate- 

 Mollusks, Holothurians, and other soft animals, de- 

 mand your first attention ; make a sketch of all rare 

 and curious forms, and wrap each specimen in a piece 

 of tin-foil before putting it into a bottle of alcohol, 

 or, if you desire to study their habits to advantage, 

 place it in a bottle of sea- water. The remainder of 

 the contents is thrown into a tub, and the dredge 

 lowered whilst it is being sorted/' When the con- 

 tents of the dredge are muddy, they must be placed 

 in wire sieves and water poured on them till the shells 

 remain visible at the bottom. The best grounds for 

 dredging are those of sand, smooth stones, sandy 

 mud, and sea- weed bottoms; rocky and coral bottoms 

 often tear the bag and break the line of the dredge. 

 The greater the depth dredged, the more important 

 the results ; and the objects secured, though few in 

 number, will frequently be either new or very rare. 

 The best description of dredge is that invented by 

 Mr. Ball, of Dublin, the cost of which is only about 

 seven shillings, its weight seven or eight pounds, 

 and which may be stowed in a carpet bag of mode- 

 rate size. In this dredge "the two scrapers are 

 each twenty inches in length by two inches in 



FF 5 



