230 THE DEPTHS OF THE SEA. [CHAP. V. 
the command of Captain Sir Leopold M‘Clintock, and 
took depths between the Feroe Islands and Iceland, 
and thence to Greenland and Labrador. The sound- 
ings were taken first by cod-line and an iron sinker 
of about 1 ewt., the line and sinker being cut off at 
each operation ; and the sounding was then usually 
repeated with the ‘ Bull-dog’ sounding-machine, with 
which large samples of the bottom were procured. 
A diary of this voyage was kept by Dr. Wallich, 
Naturalist to the Expedition, and was afterwards 
published by him as part of the extremely important 
memoir on the North Atlantic sea-bed, to which 
I have already referred. Some further questions 
having arisen as to the best line to be taken by 
an Atlantic telegraph cable, Captain Hoskyn, R.N., 
was despatched in the ‘ Porcupine’ to examine the 
curious dip from 550 to 1,750 fathoms, described 
by Captain Dayman in 1857 as occurring about 170 
miles west of Valentia. One important result of this 
cruise was the discovery of the ‘Porcupine’ Bank, 
about 120 miles west from Galway Bay, with a mini- 
mum depth of 82 fathoms. 
‘Towards the latter part of the year 1868 H.MLS. 
‘Gannet,’, Commander W. Chimmo, R.N., was 
ordered by the Admiralty to define during her 
homeward voyage from the West India Station 
the northern limits of the Gulf Stream, and to 
take deep soundings and temperatures. Thirteen 
soundings were taken with the Brooke’s machine 
over an area of upwards of 10,000 square’ miles 
from Sable Island (lat. 43° 20’ N., long. 60° W.), at 
depths varying from 80 to 2,700 fathoms. 
For many years past the American Government 
