212 THE DEPTHS OF THE SEA. [chap. v. 



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 e 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). Each 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 

 v* Inch a chamber has been made by pushing in a 

 Avooden 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- 

 in g 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 uj). Modifica- 



