146 
POrULAR SCIENCE REVIEW. 
When all the wire of the first drum is laid down, the end of 
it is roughly spliced on to the wire of the next drum, and the 
joint secured by means of the connector (fig. 7, Plate CVIII.). 
This consists of two semi-cylindrical pieces of hard wood (a), 
their flat side being grooved to receive the wire, and covered 
with a layer of india-rubber (b) to act as packing, and insulate 
the joint, in the case of a ground line, and the whole is held 
tightly together by the brass collar and screw (ccs, fig. 8). 
The line is very rapidly and easily constructed. In the case 
of a ground line it is simply paid out from the drums on the 
hand- or wheel-barrow, being buried in a shallow trench or 
elevated on poles, when it is necessary to cross a road, where 
the insulation of the cable might otherwise be injured by the 
wheels of passing vehicles. During the invasion of France the 
Prussians frequently avoided the roads in order to protect the 
line from the franc-tireurs, and made considerable detours , 
concealing it in woods, ravines and watercourses. Where the 
uninsulated wire is used, poles are erected about fifty paces apart, 
the hole to receive each pole being made by driving a sharp 
pointed iron bar into the ground with a heavy mallet. As 
soon as a pole is fixed the wire is run through the hook on the 
top of the insulator, and stretched tight by a man holding it 
over his shoulder, who keeps it in this position until the next 
pole is ready to receive it. Wherever there are trees or walls 
near the line, the work is still further lightened by dispensing 
with the poles, and merely attaching the wire to the insulators 
specially constructed for this purpose. In this way the line 
was erected for the Ashantee expedition, the negro labourers 
carrying only a light ladder to ascend the trees, a small axe to 
clear away the houghs, and a gimlet to make the hole for the 
spindle of the insulator. It never took, we are informed, more 
than five minutes to fix an insulator to a tree ; hut, in those 
few places where trees were not available, fully half an hour 
was occupied in erecting each pole, and even then it was often 
unsteady and had to be propped and guyed. 
In Europe, where there is an extensive telegraph system in 
operation in every country, there is no need of the field tele- 
graph lines extending from the front of the army to the base 
of operations. Far less than this is required. All that is neces- 
sary is to connect the head-quarters of the army with the 
nearest point on a permanent telegraph line, and in most 
European countries an army in the field would seldom, if 
ever, he more than ten miles from such a line. Ten miles of the 
field telegraph can easily he erected in half a day; indeed, 
the Austrian engineers assert that on favourable ground they 
could do the work in two hours. In most cases, of course, the 
advancing army would have to repair the permanent lines 
