DEEP-SKA KXI'I i)|;.\ I loN. 11'. • 



umIv laslu'.l tt» liu' lii-l witii |>;i( k llirca<l. Tims, in «lra^- 

 <iin«'- oviT tlu' liottoni, if tlu' ilr('»ljj;c latthcs on an inmiov- 

 ablo rock, tlio strain breaks the pack thread, the two arms 

 straij^'hten out. ami tiie (lredt;;e can usually be pulled away 

 <rom the rock without loss of frame or rope. 



The trawl, as used by the En<2;lish exi>editions, is almost 

 precisely the same as the ordinary tisherman's beam-trawl, 

 in whii h the material is collected tVom the bottom by the 

 wei.iihted edge of a net which draus behind an iron bar or 

 beam which goes upon two runners of Hat iron. For deei>- 

 sea work, however, American investigators, especially Sigs- 

 bee. Prof. Alexander Agassi/., and Prof. Verrill, have intro- 

 duced important modifications, not only of the trawl, but ot 

 the dredge, rakes, and scrapers for the bottom, and various 

 seives and otiier apparatus for cleansing and assorting the 

 material collected. 



A very important addition to the means of collecting in 

 deep water was invented by Captain Calver, R. N., during 

 the voyage of the Porcupine. This consisted in employing 

 •• swabs " or " tangles," large mops of shredded rope-yarns, 

 to sweep the bottom with, attached to the dredge to an iron 

 bar or to a weight, ^^any of the deep-sea animals^ such as 

 cru<tacca, sponges, starfish, and sea urchins, are rough or 

 prickly, and the long mops of wet threads entangled them 

 by hundreds, and came up covered with organisms when 

 the dredge had nothing but mud and a few small creatures 

 in it. A very large proportion of the animals collected 

 from the sea bottom has been obtained by the use of these 

 tangles or swabs, though many of the animals come up in 

 a masiied or broken state. 



To obtain samples of water from any dc[»th, without ad- 

 mixture of other water, brass cylinders with poppet valves 

 at top and bottom have been used. These are very heavy, 

 and, as they descend, the pressure of the water raises the 

 valves an<l the water passes steadily through until the re- 

 • piircil depth is reached. Then the line is haule<l in, re- 

 lieving the upward pie.ssure on the valves, which fall ami 

 the enclosed water is thus kept intact for analysis. 



