MUSEUM OF COMPARATIVE ZOOLOGY. 



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No. 4. — Directions for Dredging. Drawn up by L. F. de 

 Pourtales, Assist. U. S. Coast Survey. 



The results obtained in late years by dredging in various depths 

 have been such as to open a wide field to the naturalist. The laborers 

 are few as yet, and these directions are issued in the hope of increasing 

 their number by making them acquainted with the readiest modes of 

 operation. 



The dredge has as yet received but few improvements sin<*e the days 

 of Forbes. His model has proved simple and sufficient,- and would prob- 

 ably gain little by being made more complicated. Its construction will 

 be best understood by referring to the figure below, in which a a repre- 

 sents an iron frame with the edges b b sharpened and slightly turned 

 up, and forming the scrapers- The rear edge is pierced with a row of 

 holes, through which the twine, or, better, brass wire, is passed by which 

 the net is fastened. The arms c c are hooked to the short sides of the 



frame, in such a way as to allow their being folded in, for easier trans- 

 portation, and turned out in case they are caught among the rocks, as 

 will be explained further on. The net is made of strong twine with 

 small meshes, and may be three or four feet deep, according to the size 

 of the dredge. It was found convenient to have it open at the bottom, 

 and gathered and firmly tied only when in use. This gives greater 

 convenience in emptying and -washing out the bag after a haul. The 

 net is protected against the rocks and corals by an outer covering of 

 stout canvas or leather, open at the bottom. It is represented cut 



