NATURAL PHILOSOPHY. 



Notwithstanding this apparently successful result of the work, the 

 line was cut asunder soon after the connection was completed on the 

 rocks near Cape Grinez, the physical configuration of the French 

 coast heing very unfavorable. The precise point where the breakage 

 took place was about two hundred yards out to sea, just where the 

 twenty miles of electric line that had been laid down from Dover joins 

 on to a leaden tube designed to protect it from the surge beating 

 against the beach, and which also serves a similar purpose up the. 

 front of the cliff to the station upon the top. The leaden conductor, 

 it would appear, was of too soil a texture to resist the oscillation of 

 the sea, and thereby became detached from the coil of gutta-percha 

 wire that was thought to have been safely incased in it. The occur- 

 rence was, of course, quickly detected by the sudden cessation of the 

 scries of communications, though it was at first a perplexing point to 

 discover at what precise spot the wire was broken or at fault. This, 

 however, was done by hauling up the line at intervals, a process 

 which disclosed the gratifying tact, that, since its first sinking, it had 

 remained in situ at the bottom of the sea, in consequence of the leaden 

 weights or clamps that were strung to it at every sixteenth of a mile. 

 The experiment, as far as it has gone, proves the possibility of the 

 gutta percha wire resisting the action of the salt water, of the fact of 

 its being a perfect waterproof insulator, and that the weights on the 

 wire are sufficient to prevent it being drifted away by the currents, 

 and for sinking it in the sands. 



The work at present has been suspended, but will be resumed again 

 during the spring of 1851 ; a somewhat different plan, however, has 

 been proposed to be followed from that at first adopted. Instead of 

 one slender wire, it is intended to lay down cables inclosing four lines. 

 These cables will be composed of gutta-percha, four or five inches in 

 thickness, the whole incased in wire rope, chemically prepared, to 

 protect it from rot, and kyanized. There will be two of these cables, 

 each twenty miles long, and three miles apart, the whole weight rep- 

 resenting 400 tons ; and it is expected, when chained down in the 

 bottom of the sea, they will be of sufficient consistency and strength to 

 resist the anchor of a 120-gun ship. The expense of the cables is 

 estimated at 40,000. It is thought that the whole work may be 

 accomplished by May, 1851. 



APPLICATION OF THE ELECTRO-CHRONOGRAPH TO THE DETER- 

 MINATION OF THE FIGURE AND DENSITY OF THE EARTH, ETC. 



AT the Charleston meeting of the American Association, Lieutenant 

 Maury, after giving a description of Dr. Locke's electro-chronograph,* 

 remarked that it had occurred to him that, by means of it, the figure 

 and density of the earth, the height of mountains, and differences in 

 the density of the interior strata between the centre and surface of the 

 earth, at different places, might be determined. Professor Keith had, 

 by means of two globules of mercury to each, converted two other 



*?ee Ann ui! of Scientific Disrov'-nj. 1 ?">'.">. p. 121. 



