212 THE DEPTHS OF THE SEA. [ CHAP. Y. 
was at the time doing duty in the Observatory, pro- 
posed to Captain Maury a contrivance by which the 
shot might be detached as soon as it reached the 
bottom, and specimens brought up in its stead. The 
result of this suggestion was Brooke’s deep-sea’ sound- 
ing apparatus (Figs. 38 and 39), of which all the more 
recent contrivances have been to a great extent modi- 
fications and improvements, retaining its fundamental 
principle, the detaching of the weight. The instru- 
ment as devised by Mr. Brooke is very simple. A 
64 lb. shot © is cast with a hole through it. An 
iron rod A has a chamber B at the lower end, and 
two moveable arms hinged to the upper end with 
eyes to fasten two cords by which the rod is sus- 
pended; so that when the instrument is hanging free 
the arms are nearly vertical (Fig. 38). Hach arm 
bears a projecting notched tooth, and before sounding 
the shot is suspended, with the rod passing through 
it, in a canvas or leather sling c attached by cords 
whose loops pass over the teeth. The cup at the 
lower end of the rod is filled with tallow ‘ arming,’ in 
which a chamber has been made by pushing in a 
wooden plug. When the instrument strikes, the end 
of the rod is driven into the material of the bottom, 
which fills the chamber in the arming, the two jointed 
arms fall down, the loops of the sling are relieved 
from the teeth, and the rod slips through the hole in 
the shot and comes up alone with its enclosed sample 
of sediment. 
In this simplest and earliest form Brooke’s sound- 
ing apparatus had some of the defects of the cup-lead. 
The sample of the bottom was too small, and ran a 
risk of being washed out in hauling up. Modifica- 
