CHAPTER II. 
MATERIALS. 
Construction of Aerial Lines — Conducting Wires — Connections — Posts — 
Insulators, &c. 
Until the last few years the conductors were formed of 
galvanized iron wire, of from 0*12 to 0*16 inch diameter. 
From the results of ten years’ experience, some engineers 
assert that it is more advantageous as regards durability to 
expend the cost of zincing the iron wires in giving them 
instead an increased diameter. 
This expedient has moreover the advantage of increasing the 
conductivity of the wire and its power of resisting breaking 
strains. 
Wire of 0T6 inch diameter is used for inland lines, and 
wire of 0*2 inch diameter for international lines. 
The wires commonly used along the railways are of gal¬ 
vanized iron of 0T2 inch diameter. 
The wires supplied by public contract have to be delivered 
ungalvanized, in weights of at least 44 lbs. without joints or 
solderings. The ends must be as good as the middle. Each 
piece must form a separate roll of 24 inches diameter, kept in 
shape by three ties, the total weight of which must not exceed 
| oz. The outer extremity is marked by a loop. 
The wire must be entirely of the best quality, free from 
flaws and all other defects. It must be covered with a coat 
of boiled linseed oil after having passed through the draw- 
hole for the last time. Every piece showing spots of rust is 
rejected. 
A length of 33 feet of the 0T6 inch wire must weigh at 
least 2*2 lbs. and not more than 2*4 lbs. 
The weight of the same length of 0*2 inch wire must be 
