DREDGING AND HYDROGRAPHIC RECORDS. 7 



taken at the time given. The bottom temperature was taken at the 

 time of sounding. All readings by Fahrenheit thermometer. 



"Density." The water density is in all cases reduced to 15° C. 

 The density of bottom water was ascertained from a sample taken by 

 the Sigsbee water bottle. Inability to secure an accurate working of 

 this instrument led to the discontinuance of the trials. 



In the double column "Trial" is indicated the depth at which 

 apparatus was worked, as well as the duration of operation. In the 

 case of bottom apparatus this latter is the time during which it is 

 supposed to be dragging on the bottom, up to the beginning of 

 reeling in; for intermediate nets the time occupied in towing at the 

 depth shown in the depth column is indicated by the first quantity, 

 the time occupied in hoisting by the second; for surface nets the 

 time indicated is the time actually towed at the surface. 



In the double column of "Drift" is shown approximately the gen- 

 eral direction in which the gear was hauled as well as the distance. 

 The state of the currents and of the wind, with the exigencies incident 

 to the steering of the ship, make this more or less inaccurate. 



The apparatus used consisted of the usual beam trawls for all work 

 on the bottom. All intermediate and surface work was done with a 

 large tow net and small plankton or Kofoid nets, except an unsuc- 

 cessful trial of a triangular shear-board net. 



Abbreviations and Symbols. 



12' Ag 12-foot Agassiz beam trawl. The Agassiz type of beam trawl was 



used more and with better results than any other used during the 

 cruise. The runners now in use stand 4 feet in height and the 

 usual type of net carries a taut headline, making the full opening 

 available. For deep-sea work where the possibility of upsetting 

 the frame is great, a reversible net is used, with a running bolt- 

 rope passing through the clips forward of the middle of the shoes. 

 The use of this net is indicated by the abbreviation" rev." 



25 / Ag The same runners used in the 12-foot frame but spread by use of 



two light spars for beams to a 25-foot opening. Used successfully 

 on smooth bottoms. 



9' Alb.-Blk 9-foot Albatross-Blake beam trawl. 



B. A British Admiralty. 



3-bd. int a net with triangular opening operated by 3 shear boards and handled 



by a 3-part bridle from dredging cable — in no case successfully. 



2' Blk a 2-foot Blake trawl, generally used from a steam launch or rowboat; 



net made of ^-inch webbing. 



botm bottom. 



C. S Coast Survey. 



D dredging, or collecting, station. 



dip ordinary dip net on a 12-inch or 14-inch ring, with bamboo handle; 



used extensively in reef fishing with dynamite and from the gang 



plank with electric light, 

 dyn dynamite. 



