TELEGRAPHIC APPARATUS. 
263 
cautions are taken. Sir Charles Bright has contrived a 
protective apparatus founded on this very effect. It is repre¬ 
sented in fig. 186, and consists of a series of wires, stretched 
between two metallic supports, which are furnished also with 
sets of points. Two other supports have points very close to 
the former, and 
are connected with 
the earth through 
E. The line wire 
L is connected to 
the left-hand sup¬ 
port, and the ap¬ 
paratus is joined 
up through c, with 
a rod that slides 
in a guide at b. 
If a discharge of 
atmospheric elec¬ 
tricity melts the 
first w T ire, the rod 
A b drops by its 
own weight; but, 
stopped by the 
projection d, it 
comes into con¬ 
tact with the Fig. 186. 
second wire. The 
line is not therefore interrupted, and the original arrange¬ 
ment is re-established, so that the apparatus is ready to 
act again in protecting the line. This apparatus allows the 
line currents to pass until all the stretched wires have been 
successively melted, a then drops upon e, and the line is put 
to earth, whereupon it becomes necessary to renew the fine 
wires. This protector possesses the advantages of keeping for 
a long time in working order without requiring attention, and 
of effectually securing the safety of the apparatus or cable to 
which it is applied. 
