310 THE POPULAR SCIENCE MONTHLY, 



medium of communication with his base of operations and the various 

 corps of his army, it must be remembered that it is one which is con- 

 tinually liable to interruption by an enterprising enemy. Wherever 

 a general has to contend with an army well provided with good caval- 

 ry, he will find it extremely difficult to protect his telegraph-lines from 

 beino- destroyed by daring raids of his opponents. There are several 

 easy ways of making a telegraph-line temporarily useless. The sim- 

 plest and most obvious method is to pull down the poles and cut the 

 wires into pieces ; but when this is done the damage is easily detected, 



Fig. 9. 



The Field Telegraph.— a a a, line-wire supported on posts and tree ; b, Btation-wagon ; c, 



earth-conductor. 



and the repairs at once commenced. The interruption will, therefore, 

 be far more serious if it can be effected in a way which will not per- 

 mit of its exact locality being so readily discovered. This can be 

 done by cutting the wire, introducing a piece of gutta-percha, or any 

 other non-conducting substance, into the course of the circuit, and 

 connecting the ends of the wires with it, so as to give it the appear- 

 ance of one of the ordinary joints or splices of the line. At the same 

 time a few poles can be pulled down in another place, and the wires 

 cut, and the probability is that the engineers who repair the line will 

 not discover the hidden interruption of the circuit until after they 

 have restored the gap, and found that the wire is still cut somewhere 

 else, and even then the place where the non-conducting substance is 

 introduced will not be discovered until some time has been employed 

 in carefully testing the line with the galvanometer. 



But there are other dangers to telegraphic communication in the 

 field besides the mere damage to the line. If the enemy's cavalry get 

 possession of a station, they can easily send messages containing false 

 information or delusive orders to well-known officers of the opposing 

 force, while the place from which they are sent, and the assumed name 

 in which they are dispatched, will give the messages an appearance 

 of authenticity which, if it does not completely deceive the recipient, 

 will at least be the cause of considerable doubt and perplexity to him, 

 and perhaps make him hesitate to accept the accurate information or 

 authentic orders received from other sources. Again, even without 

 occupying a station, it is possible to read the messages which are 

 passing along a telegraph-line, and thus perhaps discover important 

 secrets. All that is required for this purpose is a small portable re- 

 ceiving instrument, and a few yards of copper wire to connect it with 



