uc.J ON A PIECE OF CHALK. 181 



and to indicate the nature of the sea-bottom, since this 

 circumstance greatly affects its goodness as holding 

 ground for anchors. Some ingenious tar, whose name 

 deserves a better fate than the oblivion into which it 

 has fallen, attained this object by " arming " the bottom 

 of the lead 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 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 consider- 

 able portion of the superficial layer of the sea-bottom 

 can be scooped out and 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 

 specimens were sent for examination to Ehrenberg of 

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

 microscopists 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 Globigcrince already 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 

 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 

 9 



