252 



THE DEPTHS OF THE SEA. 



[CHAP. vi. 



out. The weight of the frame of this dredge, the 

 largest we ever used, was 225 Ibs. ; it was forged by 

 Messrs. Harland and Wolff of Belfast of the best 

 Lowmoor iron. The dredge-bag was double the 

 outer of strong twine netting, the inner of bread- 

 bag. Three sinkers one of 1 cwt., 

 the other two of 56 Ibs. each were 

 attached to the dredge- rope at 500 

 fathoms from the dredge. 



The operation of sounding at a 

 depth of 2,435 fathoms in the Bay 

 of Biscay on the 22nd of July, 1869, 

 has already been described in detail. 

 When the depth had been accurately 

 ascertained, about 4.45 P.M. the 

 dredge was let go, the vessel drift- 

 ing slowly before a moderate breeze 

 (force = 4) from the N.W. The 3,000 

 fathoms of rope were all out at 5.50 

 P.M. The diagram (Pig. 50) will 

 give an idea of the various relative 

 positions of the dredge and the vessel 

 according to the plan of dredging 

 adopted by Captain Calver, which 

 FIG. 49.-The End of the worked admirably, and which ap- 



. n i -i n -i t 



pears, in fact, to DQ the only mode 



i / T T x i ,1 



which would answer for great depths. 

 A represents the position of the vessel when the 

 dredge is let go, and the dotted line A B the line of 

 descent of the dredge, rendered oblique by the ten- 

 sion of the rope. While the dredge is. going down 

 the vessel drifts gradually to leeward; and when 

 the whole (say) 3,000 fathoms of rope are out, c, w, 



Dredge-frame, showin 



the mode or attachment 



of the Bag. 



