2 VA THE DEPTHS OF THE SEA. [ CHAP. V. 
H..M.S. ‘Cyclops’ in 1857.' He used iron wire braces 
to support the sinker, as these detach more freely 
than slings of rope; he replaced Brooke’s round-shot 
by a leaden cylinder to diminish the resistance and 
thus increase the velocity in descending; and he 
adapted a valve opening inwards, to the terminal 
chamber in the rod, to prevent the washing out of 
the sample. Commander Dayman seems to have 
found the apparatus thus improved to answer well. 
He used it throughout his important survey of the 
‘telegraph plateau.’ 
The ‘ Bull-dog’ sounding machine (Fig. 40) is now 
probably the most generally known of these dredging- 
leads. This instrument is an adaptation of Sir John 
Ross’ deep-sea clamms, with the addition of Brooke’s 
principle of the disengaging weight. It was invented 
during the famous sounding voyage of H.M.S. ‘ Bull- 
dog’ in the year 1860, and Sir Leopold M‘Clintock 
gives the chief credit of its invention to the assistant- 
engineer on board, Mr. Steil.2 A pair of scoops A 
close upon one another scissorwise on a hinge, and have 
two pairs of appendages B, which stand to the open- 
ing and closing of the scoops in the relation of scissor 
handles. This apparatus is permanently attached to 
the sounding-line by the rope F, which in the figure 
is represented hanging loose, and which is fixed to 
' Deep-Sea Soundings in the North Atlantic Ocean, between 
Ireland and Newfoundland, made in H.M.S. ‘ Cyelops,’ Lieut.-Com- 
mander Joseph Dayman, in June and July, 1857. Published by 
order of the Lords Commissioners of the Admiralty. London: 1858. 
2 Remarks illustrative of the Sounding Voyage of H.M.S. ‘ Bull- 
dog’ in 1860 ; Captain Sir Leopold M’Clintock commanding. Pub- 
lished by order of the Lords Commissioners of the Admiralty. 
London: 1861. 
