DEEP-SEA SOUNDING. 627 



creased from the surface to the bottom. At the depth of 3,000 fathoms, 

 for instance, the pressure upon a square inch is nearly 8,000 lbs., but the 

 column of water of 18,000 feet is only shortened by about 160 feet. At a 

 depth of 2^ miles the increase of Density is not equal to the difference in 

 the density between fresh and salt water. Dr. W. A. ililler calculated it 

 would at that depth be equal to one forty-seventh of its volume, while sea- 

 water, at the mean specific gravity of 1-027, is one thirty-seventh heavier 

 than fresh water. There is, therefore, not the slightest difficulty in under- 

 standing that the sounding-lead or telegraph cable would sink uniformly 

 from the surface to the greatest depths ; and not only such heavy wei^ts, 

 but even that the delicate organisms and remains of microscopic animals 

 which have lived on the surface, may quietly sink to the bottom, and there 

 add to the immense deposits which are now shown to exist everywhere 

 over the ocean-bed. 



But little importance can be attached to deep-sea soundings taken pre- 

 viously to the beginning of the nineteenth century. Among the earliest 

 reliable experiments, perhaps the first, of these deep-sea soundings, is that 

 recorded by Sir James Eoss, who, during the Arctic Expedition of 1818, 

 obtained specimens of the bottom from depths exceeding 1,000 fathoms. 

 On November 13th, 1822, Captaan (afterward General Sir) Edward Sabine, 

 when about midway between the Caymans and Cape Antonio, in the 

 Caribbean Sea, sank a cylinder and obtained the temperature at a depth 

 exceeding 1,000 fathoms. This was followed by Captain Wauchope, in 

 H.M.S. Eurydice, who gained water from a depth of about 1,800 fathoms. 

 After this, many experiments were tried with more or less success, but 

 there can be little doubt that many of the early results are not trustworthy, 

 and are greatly in excess of the truth. At first it was not always tried to 

 recover the lead, and the line employed was of very inferior character ; 

 and it was thought that at very great depths the friction of the water was 

 sufiQcient to entirely arrest the descent of the weight. 



The first attempt to use wire in deep soundings, as a substitute for 

 hemp cord, was in 1838, during the cruise of the United States Exploring 

 Expedition, under Captain Wilkes, but it was unsuccessful, owing to its 

 excessive weight. On August 3rd, 1848, Captain Barnett, R.N., H.M.S. 

 Thunder, when in about lat. 4P 19' N., long. 44° 16' W., between the 

 Azores and Newfoundland, tried a line of iron wire, varying in size from 

 Nos. 1 to 5, of 4,000 fathoms in length, wound on a small reel, the smallest 

 part first, with a weight attached of 61 lbs. It broke at 2,000 fathoms, 

 which ran out in 20"" 53*. This experiment was suggested by Lieutenant 

 Mooney. 



But the greatest length of wire line sent down was that effected by 

 Lieut J. C. Walsh, in the U.S. schooner Taney, on November 15th, 184P, 

 to a depth of more than 5,700 fathoms (34,200 ft., or more than 6 statute 

 miles), without finding bottom, as was supposed, in lat. 31° 59' N., long. 

 58° 43' W., in the vicinity of the assigned position of the rocks called the 

 False Bermudas. "The wire broke at this length, 5,700 fathoms, at the 

 reel, and was lost. It preserved the exact plumb-line throughout the 

 sounding ; there was a steady, uniform increase of weight and tension ; no 

 check whatever any instant of its descent." This experiment, however, 



