THE FIELD TELEGRAPH. 
147 
which would be partially destroyed by the retreating forces, 
and in this way twenty-five miles of wire were often erected by 
the Prussians in a single day. As soon as an army moves 
forward, the field telegraph line previously erected is taken 
down and re-coiled on the drums, while a fresh line is laid 
from the new head-quarters to the nearest permanent tele- 
graph. This is done with a view to economising the material, 
an enormous amount of which would have to be carried with 
the army, if the lines it left behind it in its advance were not 
removed, and the poles, wire and insulators employed in their 
construction again utilised. The hand-barrows of the Austrian 
telegraph corps are designed to be used in re-coiling as well as 
uncoiling the wire ; and for this purpose are fitted with a crank 
handle and ratchet-wheels, so as to enable a man to turn the 
drum and wind the cable upon it. 
Besides the ordinary field telegraph companies, the French 
army includes a mountain telegraph corps, organised with a 
view to operations on the mountainous frontiers of the south, or 
to be ready to carry a line over a range of hills in an ordinary 
campaign, thus avoiding a long detour in the valleys, or secur- 
ing lateral communication with troops divided from the main 
army by the hills. As the mountain . line would have to be 
laid along narrow rocky paths, and through lofty passes, all 
carriages and waggons are dispensed with, and their place is 
taken by a train of mules. In a mountain telegraph company 
several of the mules are each laden with two drums of the insu- 
lated cable, the instruments and batteries are carried on pack- 
saddles on the backs of others, and others again transport the 
baggage, provisions, and forage of the company, and also a 
light tent to form a station whenever messages are to be sent 
along the line. 
While the field telegraph affords a commander a rapid and 
certain 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 continually liable to interruption by an 
enterprising enemy. Wherever a general has to contend with 
an army well provided with good cavalry, he will find it 
extremely difficult to protect his telegraph lines from being 
destroyed by daring raids of his opponents. There are several 
easy ways of making a telegraph line temporarily useless. 
The simplest 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, 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 permit 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- 
