On a Piece of Chalk 81 





 with a lump of grease, to which more or less of the sand 



or mud, or broken shells, as the case might be, adhered, 

 and was brought to the surface. But, however well 

 adapted such an apparatus might be for rough nautical 

 purposes, scientific accuracy could not be expected from 5 

 the armed lead, and to remedy its defects (especially 

 when applied to sounding in great depths) Lieut. Brooke, 

 of the American Navy, some years ago invented a most 

 ingenious machine, by which a considerable portion of the 

 superficial layer of the sea-bottom can be scooped out and 10 

 brought up, from any depth to which the lead descends. 



In 1853, Lieut. Brooke obtained mud from the bottom 

 of the North Atlantic, between Newfoundland and the 

 Azores, at a depth of more than 10,000 feet, or two 

 miles, by the help of this sounding apparatus. The 15 

 specimens were sent for examination to Ehrenberg of 

 Berlin, and to Bailey of West Point, and those able micros- 

 copists found that this deep-sea mud was almost entirely 

 composed of the skeletons of living organisms the greater 

 proportion of these being just like the Globigerina already 20 

 known to occur in the chalk. 



Thus far, the work had been carried on simply in the 

 interests of science, but Lieut. Brooke's method of sound- 

 ing acquired a high commercial value, when the enter- 

 prise of laying down the telegraph-cable between this 25 

 country and the United States was undertaken. For it 

 became a matter of immense importance to know, not only 

 the depth of the sea over the whole line along which 

 the cable was to be laid, but the exact nature of the bottom, 

 so as to guard against chances of cutting or fraying the 30 

 strands of that costly rope. The Admiralty consequently 

 ordered Captain Dayman, an old friend and shipmate of 

 mine, to ascertain the depth over the whole line of the cable, 

 and to bring back specimens of the bottom. In former 



