DEPTHS OF THE OCEAN 



Method of 

 dredging and 

 trawling. 



r" 



machine (Fig. 3) was the one in general use on board the 



" Challenger." 

 Time required From the Narrative of the Cruise we get the following 

 Sje^^v^ale"^'" particulars regarding the time - 



required for sounding in deep 



water : — 



Station 81. Began sounding 5 

 P.M. ; found bottom at 2675 fathoms ; 

 finished hauling in at 6.20 P.M. 



Station 225. Began sounding 

 12.30 P.M. ; found bottom at 4475 

 fathoms ; finished sounding at 3 P.M. 



We see, therefore, that sound- 

 ing in about 3000 fathoms took 

 nearly an hour and a half, where- 

 as for about 4500 fathoms two 

 and a half hours were required, 

 which must be considered very 

 quick work. On the same line 

 and with the same arrangement 

 as for sounding, series of tem- 

 peratures were taken and deep- 

 water samples obtained. 



Heavy lines and strong 

 accumulators were, however, 

 necessary for the dredge and 

 trawl, which were each fastened 

 to a stout 2-inch line, paid out 

 through a block attached to the 

 big accumulator (see Fig. 2). 

 From 300 to 500 fathoms first 

 ran out, then a weight of about 

 80 kilos ' was allowed to slide 

 down the line till it was stopped 

 just a little in front of the appli- 

 ance. The weight consequently reached the bottom before 

 the appliance, with the result that this latter merely skimmed 

 the ocean floor. 



All this time the ship lay with her head to the wind to 

 enable the appliance to reach the bottom, for which operation 

 about three hours were required. When all was in readiness 

 the ship was allowed to drift with the wind abeam, and thus 

 towed the dredge or trawl along. 



Fig. 



Baillie Sounding Machine. 

 The tube (/) was generally made to project 

 18 inches below the weights {e}. 



