3.— DESCRIPTION OF A CLOSING TOW-NET, FOR SUBMARINE 

 USE AT ALL DEPTHS. 



By C. II. Townsend, 

 Assistant, United States Fish Commission. 



Recent experiments with closing tow-nets in submarine explorations 

 have yielded so much accurate information concerning the vertical range 

 of pelagic life that the construction of the Tanner intermediate tow-net 

 in 1891 } may be said to have inaugurated a new era in the study of 

 the pelagic fauna, characterized by exact knowledge of the depth of 

 the forms collected. 



The vertical distribution of the pelagic life gathered with the open 

 tow-nets of the Challenger expedition has necessarily been conjectural, 

 the nets employed having been dragged open at all depths. Since 

 then European investigators have employed several devices for closing 

 submarine tow-nets, but direct evidence as to their reliability, so far as 

 the writer is aware, seems to be lacking. 



Open tow-nets of different forms have long been employed by the 

 United States Fish Commission, while a closing collector, although of 

 very limited capacity (the Sigsbee gravitating trap), has done service 

 on the Coast Survey steamer Blalce; but it was not until 1891 that 

 a closing tow-net of large size was brought iuto use. The Tanner 

 tow-net, closing tightly at any depth desired, has proved its efficiency 

 during recent explorations conducted by the Fish Commission and by 

 Mr. Alexander Agassiz, but its large size and somewhat complicated 

 construction have prevented its use except by steam power from large 

 vessels. 



While towing a light surface-net behind one of the small boats of the 

 Albatross in an Alaskan harbor in the summer of 1894, the idea of a 

 very simple closing-net presented itself, which was at once experimented 

 upon and gave satisfactory results. I at first used it in moderate depths 

 only, but subsequently, having made one of heavier form than at first 

 employed, the principle was found applicable to deep-sea work as well 

 as near the surface. 



'Tanner, Rept. U. S. Fish Com. 1889-91, pp. 259-260. Bull. U. S. Fish Com. 1894, 

 pp. 143-151. 



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