140 THE SEA. 



instrument could not be constructed of sufficient 

 strength to withstand the enormous pressure of a 

 weight equal to some hundred atmospheres. 



It was proposed by one mechanician to adapt the 

 principle of the magnetic telegraph to deep-sea sound- 

 ings. The wire, properly coated, was to be laid up 

 in the sounding-line, and to the plummet was attached 

 machinery, so contrived that at the increase of every 

 hundred fathoms, and by means of the additional 

 pressure, the circuit would be restored, and a mes- 

 sage would come up to tell how many hundred fathoms 

 the plummet had travelled down. This brilliant idea 

 could not, however, be made sufficiently simple for 

 practical avail. 



Lieutenant Maury had a curious contrivance exe- 

 cuted under his own direction. To the lead was 

 attached, upon the principle of the screw-propeller, 

 a small piece of clock-work for registering the num- 

 ber of revolutions made by the little screw during the 

 descent ; and it having been ascertained, by experi- 

 ment in shallow water, that the apparatus in descend- 

 ing would cause the propeller to make one revolution 

 for every fathom of perpendicular descent, hands, pro- 

 vided with the power of self-registration, were attached 

 to a dial, and the instrument was complete. Mr 

 Maury says that it worked beautifully in moderate 

 depths, but failed in blue water, from the difficulty 

 of hauling it up if the line used were small, and of 

 getting it down if it were large. But we do not see, 



