.V/A' \VJLLIAM SIEMENS, F.R.S. 347 



i he invention of two sounding machines ; the one being devised 

 for ascertaining great depths very accurately, in less than one- 

 quarter the time formerly necessary, and the other for taking 

 (!<]>' hs up to 130 fathoms without stopping the ship in its onward 

 course. In both these instruments steel pianoforte wire is used 

 instead of the hempen or silken lines formerly employed ; in the 

 latter machine the record of depth is obtained not by the quantity 

 of wire run over its counter and brake wheel, but through the 

 indi rations produced upon a simple pressure gauge consisting of 

 an inverted glass tube, whose internal surface is covered before- 

 hand with a preparation of chromate of silver, rendered colourless 

 by the sea-water up to the height to which it penetrates. The 

 value of this instrument for guiding the navigator within what he 

 calls " soundings " can hardly be exaggerated ; with the sounding 

 machine and a good chart he can generally make out his position 

 correctly by a succession of three or four casts in a given direction 

 at given intervals, and thus in foggy weather is made independent 

 of astronomical observations and of the sight of lighthouses or the 

 shore. By the proper use of this apparatus, accidents such as 

 happened to the mail steamer Mosel, not a fortnight ago, would 

 not be possible. As regards the value of the deep-sea instrument 

 I can speak from personal experience ; on one occasion it enabled 

 those in charge of the Cable s.s. Faraday to find tho end of an 

 Atlantic Cable, which had parted in a gale of wind, with no other 

 indication of the locality than a single sounding, giving a depth 

 of 950 fathoms. To recover the cable a number of soundings in 

 the supposed neighbourhood of the broken end were taken, the 

 950 fathom contour line was then traced upon a chart, and the 

 vessel thereupon trailed its grapnel two miles to the eastward of 

 this line, when it soon engaged the cable 20 miles away from the 

 point where dead reckoning had placed the ruptured end. 



Whether or not it will ever be practicable to determine oceanic 

 depths without a sounding line, by means of an instrument based 

 upon gravimetric differences, remains to be seen. Hitherto the 

 indications obtained by such an instrument have been encourag- 

 ing, but its delicacy has been such as to unfit it for ordinary use 

 on board a ship when rolling. 



The time allowed me for addressing you on this occasion is 



