116 Submarine Telegraphy. 



according to the supposed excellence of one or more of tlie 

 three parts above named, or according to the purpose for which 

 they are intended. Thus we have Needle telegraphs, so called 

 because their indications are made by the deflections of a 

 magnetic needle ; Printing telegraphs, which actually print on 

 a slip of a paper, or other material, the signs or letters indi- 

 cated ; Alphabetical telegraphs, so called because they point 

 to, or print the letters of the ordinary alphabet ; Magnetic 

 telegraphs, which derive their name from the motive power, 

 which is a magnetic and not a voltaic battery; Submarine 

 telegraphs, intended to convey signs by means of wires or 

 cables laid at the bottom of the ocean bed, and so forth. 



To this last species of telegraph we confine our attention 

 in the present paper; and here we shall find the main interest 

 to lie in the construction of the conducting wire, and its safe 

 submersion in the bed of the ocean ; for the difficulties attend- 

 ing the construction of a continuous wire of several miles in 

 length, its perfect insulation, and safe submersion in the bed 

 of the ocean, are so great, that every experiment of the kind 

 is watched with the deepest anxiety by all concerned in its 

 success. We shall not, therefore, stop to examine the source of 

 electric power, or the indicating instruments at each end of 

 the system, it will suffice for the occasion to observe that they 

 are the same as in all other telegraphs in use, and are not 

 likely to affect the success of any undertaking where the con- 

 tinuity and insulation of the conducting wire are perfect. The 

 batteries may be either voltaic or magnetic, and the indicating 

 instruments may resemble any of those ordinarily seen in the 

 room of a telegraph office, but the conducting wire must be 

 specially adapted to the circumstances of each particular case. 



Among the circumstances which affect the well-being of a 

 conducting wire in the submarine telegraph, the most im- 

 portant are the nature of the ocean bed, the action of the sea- 

 water, and the attacks of marine animals. 



First, as to the ocean bed. If the sea-bottom be very 

 uneven, rising here into mountains, and falling there into 

 valleys, a much greater length of wire will be required to 

 reach a given distance than would be necessary if it could be 

 laid down in an even line. So great was the difference iu the 

 first cable laid across the Straits of Dover, that when the 

 whole of it was payed out, the shore was not reached, and an 

 additional portion had to be made before a landing could be 

 effected. In tho present Atlantic cable 630 miles have been 

 allowed to make up any deficiency which might arise from the 

 same cause, and this will explain what appears to have puzzled 

 some people when they read the account of tho submersion of 

 the cable during the past month. The telegrams ran after 



