BULLETIN 39, UNITED STATES NATIONAL MUSEUM. 



[28] 



over and get iuto the mouth of it, it is usually best to tie tlie lateral 

 edges of the upper aud lower flaps to each other, in one or two places 

 with stout twine,which holds them in their place. The net itself can 

 be turned inside out, and the dredge emirtied without disturbing the 

 flaps. 



To have a dredge constructed, one should go to a blacksmith and not 

 to a machine shop. The size of the rectangle forming the frame will 

 differ according to the necessities of the case. If the dredge is to be 

 used in a small boat in shallow water, it may be smaller and lighter 

 than if it is to be used in a larger vessel, a sail-boat or by the aid of 

 steam. The average dredge, for moderate depths of water to be used in 

 a row boat, should be made of half-inch bar iron. The bar should be 

 about three inches in width, and its length should correspond to the 

 total circumference of tlie rectangle to be made, with a small allowance 



Figs. -L and 5. — Dredge frame, showing arraugemeut of arms. 



for welding. The holes for the rivets are to be made and the beveling- 

 of the upper and lower edges is to be done by the smith before he bends 

 his bar into a rectangle. After the rivet-holes have been punched, and 

 the edge prox)erly fashioned, two half-inch holes should be made in that 

 portion of the bar intended to form the vertical sides of the frame. 

 These holes are intended for the arms. After all the holes have been 

 punched, the bar may then be bent into the proposed rectangle and the 

 ends welded solidly together. A convenient form is 20 inches from side 

 to side, and 5 inches in height. The arms should be made of nail-rod 

 and inserted in the holes which have been made for them, but the circle 

 which the ends describe through these holes, inclosing the front edge 

 of the frame, should be sufficiently large to allow the arms complete 

 freedom of motion. The form of the arms will be seen from the figure. 

 When in use they should form with the frame an equilateral triangle^ 



