112 
THE TELEGRAPH. 
a 
a 
cast-iron cap, e ; 5th, 
wrought - iron lightning - con¬ 
ductor,/. In India the natives 
have frequently taken possession 
of the spikes of the lightning con¬ 
ductors to make into weapons by 
fixing them at the end of a bam¬ 
boo ; the spikes are therefore 
now riveted to the caps. The 
form of iron post that has 
found most favour in Europe, and 
is also met with in all parts of 
the world, is Siemens Brothers’ 
tubular post, shown in fig. 46. 
It consists of four parts1st, 
the base, a ; 2nd, the foot, £, 
made of cast-iron; 3rd, the upper 
tube, c , of wrought-iron; 4th, the 
lightning conductor, d , also of 
wrought-iron. The base is made 
of iron plates riveted together, 
and unites great firmness with an 
elasticity that enables it to yield 
to sudden or excessive strains. 
In the little square platform in 
the middle of it are four holes 
through which pass the screw 
bolts for fastening the base to 
the cast-iron foot. This last 
diminishes in diameter as it 
passes upwards, and terminates 
in a collar to receive the upper 
tube of the post. The latter is 
fixed in its place by a cement 
composed of sulphur and oxide 
of iron. It is made of a plate 
of iron bent round and the edges 
welded together, and it is provided at the top with a socket 
for receiving the lightning conductor. 
These posts vary in size according to the strain they are 
Fig. 46. 
