252 THE DEPTHS OF THE SEA. [cHAP. VI. 
out. The weight of the frame of this dredge, the 
largest we ever used, was 225 lbs.; 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 ewt., 
© the other two of 56 lbs. each—were 
| attached to the dredge-rope at 500 
fathoms from the dredge. 
The operation of sounding at a 
depth of 2,485 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:) fromthe N.W. The 3,000 
fathoms of rope were all out at 5.50 
pM. The diagram (Fig. 50) will 
| give an idea of the various relative 
Ht Hi i positions of the dredge and the vessel 
i | \ Al || according to the plan of dredging 
\\ ie i adopted by Captain Calver, which 
ive. 49 The End of the WOFked admirably, and which ap- 
Dredge frame, showing pears, in fact, to be the only jmede 
siete 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 
tension 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, 
