NATURALISTS' ASSISTANT. 



cover, so that it will not catch and tear on rocks, etc., on the 

 bottom. Iron handles are attached to the frame, and to one 

 of these the dredge rope is tied ; the other handle is made 

 fast to the rope by means of a bit of " spun yarn " or lighter 

 cord, as shown in fig. 13. The object of this is that, if the 

 dredge be caught on a rock, the smaller cord will break and 

 the dredge free itself. A weight should be attached to the 



rope a short distance 

 (six to twelve feet) in 

 front of the dredge, so 

 that its mouth may be 

 kept on the bottom. The 

 length of rope paid out 

 should be about twice 

 the depth of the water 

 in which the dredging is 

 conducted. In dredging 

 from a sail-boat it is best, 

 if possible, to take ad- 

 vantage of the currents. 

 Put the dredge over the 

 bows, taking care that it 

 FlG - I3 ' does not turn inside out 



or foul while going down, then let the boat drift as though 

 she were dragging an anchor. Where currents are not strong 

 enough the boat head should be turned toward the wind, so 

 that it will just move through the water, and then put the 

 dredge over the windward side near the stern. The boat will 

 then drift slowly, drawing the dredge over the bottom. 



