WITH THE MICROSCOPE. 149 



The Draghook, fig. 230, consists of three groups of stout iron 

 hooks welded to a horizontal bar having an eye in the middle, to 

 which a stout rope is fixed. This is let down among the roots and 

 fronds of the coarse seaweed, on which many microscopic animal and 

 vegetable forms are parasitic, and when entangled is hauled up with 

 the captured specimens. 



The Naturalist's Dredge, fig. 228, however, produces the richest 

 harvest from the sea. It is made of a wrought-iron rectangular 

 frame, from which two scrapers project at an angle, on each side, 

 and to which two handles, terminating with four links of chain, are 

 hinged to each end so as to allow of some freedom of motion, and 

 the dredge being easily packed into a small space. To this frame a fine- 

 meshed tanned net is fixed by copper wire, and to prevent this from 

 being caught when dragging over a rough sea bottom, it is guarded 

 by two flaps of coarse sail cloth which hang on either side. The 

 mouth is made narrow to prevent heavy stones from entering. A 

 rope strong enough to anchor the vessel in smooth water, and long 

 enough to prevent the dredge skimming or bumping over the bottom, 

 yet not so long as to allow it to bury itself in soft sand or mud, is 

 required. Its length should be about double the depth of the water 

 dredged. The rope should be firmly tied to one ring only, and then 

 the ring of the other handle should be braced to its fellow by a piece 

 of spun yarn, so that in the event of the dredge fouling, by putting 

 extra way on to the boat the string will yield and allow the two 

 handles to open, and thus the dredge will easily free itself. On 

 lowering the dredge, it is evident that it is a matter of indifference 

 which side rests on the ground, and in this lies its advantage over the 

 common dredge. It may be used in a rowing boat in smooth shal- 

 low water near shore, but a small sailing boat is preferable in depths 

 over tenfathoms. The towingrope is coiled up at the bottom of the boat, 

 and its free end is made fast to one of the cross seats. The dredge is 

 thrown over to windward near the stern, and when sufficient line has 

 run out a turn or two is made round a " belaying-pin " to make it 

 taught. The line should be held in the hand so that the owner 

 can feel at once if anything goes wrong. When the dredge is lifted, 

 its contents should be emptied into a sorting tray, fig. 229. This 

 consists of a coarse wire sieve C, which retains all large specimens, 

 stones, &c., but allows small or delicate ones to pass into a perforated 

 zinc sieve F, which retains all objects over ^-inch diameter, but 

 allows the sand or mud to be washed into the lower tray which is 

 furnished with a double bottom formed of fine webbing stretched on 

 a frame. The water poured over the sieves to facilitate this operation 

 is carried off by a flexible tube. Mr. Highley makes all these trays 



