62 On the Municipal Electric Telegraph, 
to avoid loss by imperfect insulation, and the multiplication of 
places of support, where alone, interference with the wires is 
possible. In Boston it has not been considered prudent to extend 
the stretches of the Alarm System generally over two hundred 
feet, on account of the occasional storms of snow and rain in the 
winter, in which great accumulations of ice are formed upon the 
wires. A single stretch however of the House line, of over 800 
feet between the towers of neighboring churches, has continued 
undisturbed for two years. In cities in this country South of 
Boston, stretches of 300 or 400 feet may be allowable. 
From the strength of the conductors they can not be easily 
interrupted either by accident or design, and in the latter case 
recourse must almost necessarily be had to instruments. The 
place of such violence would be apparent, and the broken wire, 
from its weight and tension, would fall at once to the ground, 
Detection would therefore be easy. The wires, used for an im- 
portant public object, would, of course, be protected by law. The 
police and members of the fire department should be instructed 
at once to report a broken wire that it may be repaired. 
As the interruption of a wire is a possible, though not a proba- 
ble or frequent occurrence, the principle of Double Conductors 
must be introduced into any System, in which absolute uni- 
formity of action is required. ‘This is necessary in the chro- 
nometrie application of the Telegraph, where electric pulsations 
are sent over the wires every second to measure and mark uni- 
form time on a hundred dials. It is equally necessary in the 
ystem, there are two conducting wires following differ 
ent routes. A proportionate increase of conducting power is al 
incidental advantage of this use of two-fold wires 
By a strict regard to the principles of construction and arrange- 
ment, which have thus been considered, the interruption of the 
age of the Municipal Telegraph. becomes practically impos- 
sible. 
e ground can not be used as any part of the circuit of the 
Municipal Telegraph without introducing a source of irregularity: 
A connection, accidentally or intentionally made between the 
wire and the ground, in such case, would complete an “ open” 
circuit, or throw part of a “closed? circuit out of use. A dupli- 
cate conductor would also cease to be an advantage or security; 
where the circuit would be permanently completed by the intef- 
ruption and falling of a Single wire to the ground. In the Fire. 
Alarm System, the circuits are composed exclusively of wires; 
and these, in the process of erection, are separated as widely aS 
possible, especially in the case of corresponding wires, whose 
