630 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



VII. THE UNIVERSAL TELEGRAPHIC NETWORK. 



It is scarcely necessary, perhaps, to insist on the importance of 

 electric telegraphy in matters of private, public, and international 

 interest. This application of one of the branches of physics, which 

 has made so great progress during the last century, is so brilliant a 

 conquest of human ingenuity over time and space, that no one can 

 doubt the enormous range of its usefulness. Confined at first to 

 public and governmental correspondence, or diplomatic despatches, 

 it has received all its development since it has b3en required for 

 serving private interests. The use of the telegraph has been since 

 then prodigiously extended, and it still daily increases, in proportion 

 as the number of stations is augmented. Thus in France alone, twenty 

 years ago, seventeen telegraphic stations sent off annually ssarcely 

 9,000 messages, while now, 3,500 stations send more than six 

 millions. 



Telegraphic communication not only serves for the purposes of 

 families or friends, but still more for purposes of business, commarce, 

 arts, and speculations in shares. So far for private interests. In 

 diplomacy, war, public works, administration, politics, and police, it 

 is continually made use of. In a higher and more serene domain, 

 that of science, it renders the greatest service, by furnishing astrono- 

 mers with the means of determining the longitude with precision, of 

 signalling to all the observatories the discovery of new stars, comets 

 and'planets, and thus gaining weeks in verifying and registering the 

 discoveries. In meteorology the telegraph announces coming storms, 

 and the rising of water, sends warnings to seaports of squalls, and so 

 supplies navigation with precious information such as has already 

 saved ships and cargoes from disaster. 



This enumeration of the services rendered by telegraphy is very 

 incomplete. But the best way to demonstrate its importance is to 

 transcribe here a few figures indicating the actual state of the net- 

 work of air and submarine lines which are now at work all over the 

 surface of the earth. 



The length of lines over the whole earth is very nearly 400,000 

 miles, that is, sixteen times the earth's circumference. In this total 



