DEEP-SEA INVESTIGATION. 61 



fitted at its upper end with peculiar disengaging hooks. The weight 

 was slung to these hooks by means of a wire which passed from a ring 

 slipped over the rod under the weight, up on each side of th cannon- 

 ball to the hooks. The sounding-line was attached to eyes in these 

 hooks, and, as long as the lower end of the rod was not resting on 

 anything, the weight was kept securely in its place, and was available 

 for taking out the sounding-line. As soon, however, ias bottom was 

 reached, and the rod came to be supported on its lower end, the hooks 

 at the upper end fell forward, and allowed the wire to disengage itself. 

 The weight was thus released, and, on the line being pulled up, the 

 rod came away through the perforation of the shot, and brought with 

 it specimens of the mud in small quill tubes fitted in a recess in the. 

 lower end of the rod. This apparatus has been improved by substi- 

 tuting a tube for the rod, and so arranging the attachment of the 

 weight that it shall continue till the hauling in is begun, whereby its 

 mass and momentum are available for forcing the tube as deep into 

 ' the ground as possible. Captain Shortland devised another modifica- 

 tion of the apparatus in 1868, for the soundings between Bombay and 

 Aden. The essential part was the insertion of two butterfly valves 

 in the lower end, and two conical valves opening upward in the middle 

 of the tube, between which a sample of the bottom water is secured, 

 while a specimen of the mud is brought up in the lower segment of 

 the tube. It was used with general satisfaction during the first year 

 of the cruise of the Challenger. The chief objection to it was founded 

 on the smallness of the samples of bottom which it brought up. This 

 machine, the " Hydra," was replaced after the first year by the " Bai- 

 ley," an apparatus having a larger tube fitted to bring up more consid- 

 erable samples of mud. 



An apparatus which the author has devised for sounding the Scot- 

 tish lakes, and found to act well, consists of a straight brass tube an 

 inch in diameter, carrying a shoulder about one foot from the lower 

 end. A cylindrical leaden sinker of suitable weight is slipped over 

 the upper end, and rests on the shoulder. The line is made fast to 

 an eye at the top of the tube, and the part of the tube below the 

 shoulder can be unscrewed, and the mud which it has brought up 

 squeezed out. The tubes bury themselves readily in soft mud and 

 clay, and bring up considerable samples. 



It is necessary, in making a sounding in deep water, to load the 

 end of the line with such a weight that in the deepest water that may 

 be reasonably expected the velocity of descent shall not be dimin- 

 ished to an excessive extent by the friction of the increasing length 

 of line in passing through the water. Wire has been largely employed 

 for the line, and has great advantages in this respect over hemp. For 

 example, in water of fifteen hundred fathoms a sinker weighing three 

 hundred-weight is twenty minutes in reaching the bottom, with the 

 best hempen sounding-line ; while with wire and a sinker of thirty 



