_and its application to Fixe Alarms. 61 
The Conductors commonly used consist of iron wire, supported 
by insulators upon the houses. These wires, where erected with 
a view to permanence and stability, should be of the best Swedish 
iron, and be limited in size and strength only by the strength of 
the supports which it is practicable to employ. The largest iron 
wire in common use within our cities is No. 9, which weighs about 
325 lbs. to the mile. The construction of the Alarm System in 
Boston, was commenced with wire No. 8, weighing about 400 
Ibs. to the mile. It was found however that the brickwork would 
not often hold the insulators, with the weight of so heavy a wire, 
without the intervention of brackets of unusual strength, into 
which the insulators were screwed. In the South Boston Cir- 
cuit, wire No. 10, weighing rather less than 300 Ibs. to the mile, 
‘Was employed, as giving on the whole greater security, without 
exceeding very much, by the mode of support, the usual cost of 
such works. ‘The length of the wire in the Municipal Telegraph 
of Boston is about 49 miles, and it has probably been erected 
with greater care and thoroughness than any similar structure in 
the country. , 
In a System, however, of such public importance, and designed 
to be permanent in its character, no effort should be spared to 
give a massive strength to every part, and ample provision should 
be made for the careful and judicious survey of routes and selec- 
ion of the places of attachment for the wires. It is also to be 
considered that a structure liable to frequent derangement, would 
a source of just annoyance to real estate holders in the City, 
Whose buildings are needed for the support of insulators. For 
these reasons, Mr. Farmer would recommend the appropriation of 
$150 per mile for the conductors of the Municipal Telegraph, so 
as to allow the use of large and often elevated brackets, support- 
ing No. 8 wire in carefully selected positions. This is a more 
elaborate method of construction than has yet been attempted. 
The wire of the same size, erected in Boston, has cost about $73 
per mile, and should possess great strength and stability after it 
been tested by exposure, and any weak parts have been 
replaced, 
in the selection of buildings for the support of the Conductors, 
Public edifices, such as churches, school houses, &c., should: be 
preferred, and next to these, lofty and isolated buildings, in order 
to Temove the wires, as much as possible, from danger of interfer- 
€. ‘Two wires, or, at Jeast, related wires, should not be at- 
tached to the same building or block of buildings. 'The Con- 
ductors should be so much elevated above the roofs of houses, 
that their insulation should never be impaired by contact with 
fallen snow ail ok SRE ee 
. 
_ The stretches of wire, in the Municipal ‘tes 
8S long and few as practicable, consistent with 
