334 THE SCIENTIFIC PAPERS OF 



the apparatus described this evening commends itself without 

 any words from me. There are many difficulties which present 

 themselves at first sight against the use of wire for soundings, 

 but these have been met in the most perfect and ingenious 

 manner. First of all, to get wire of such uniform strength as 

 to reach to a depth of 3 miles required very considerable atten- 

 tion. Nevertheless, pianoforte wire offers extraordinary strength 

 and toughness, and is, undoubtedly, the right material ; but how 

 to join these wires in such a manner as to be reliable was a 

 matter of great consideration, and that difficulty has been met 

 in the most perfect manner. Then the mode of checking the 

 motion of the drum by a single rope, although in itself involv- 

 ing only a Prony brake, is a very ingenious mode of adapting 

 a means to a particular end, and this is brought in usefully for 

 telling in the most absolute manner when the weight strikes 

 the bottom. As Sir William Thomson says, attaching the weight 

 itself to a piece of line, and adjusting the friction in such a 

 manner as that the motion of the machine is stopped the moment 

 the lead reaches the bottom, is another stage in the perfection of 

 this method of sounding. There are other points of great in- 

 genuity in the apparatus now before us. With regard to the 

 practical value of taking deep-sea soundings by wire I have no 

 doubt. I have myself made deep-sea soundings, and I know 

 that in depths of 2,400 or 2,700 fathoms it occupied from four 

 to five hours, and it was a difficult matter sometimes to keep 

 the ship over the line. The lateral friction of the line in the 

 water was so great that the lead did not pull and therefore the 

 ship had to be kept over the line. Instead of occupying five 

 hours this apparatus completes a deep-sea sounding in about 35 

 or 40 minutes, and that is a matter really of the highest im- 

 portance, especially in making soundings for submarine cables, 

 where time is a great object. Flying soundings are matters of 

 great interest. I did not quite follow Sir William Thomson's 

 illustration. He shows that the lead touches the ground at a 

 distance at least equal to the depth. I should have thought 

 the point where it struck the bottom would be a distance from 

 the stem of the ship not exceeding one-fourth part of the depth 

 of the water, and the result would be that this (pointing to the 

 board) would be 10 or even 50 per cent, longer than the verti- 



