260 
THE TELEGRAPH. 
The quadruplex system consists in again duplexing the 
system by which two despatches are simultaneously sent in one 
direction. Stark, of Vienna, had solved this problem by 1855, 
for by means of tw r o batteries and two keys properly arranged, 
he obtained a differential magnetic effect on the two relays at 
the receiving station, by means of which two independent com¬ 
munications could be sent in the same direction simultaneously. 
We do not propose to describe this system at length, or the 
similar one of Gerrit Smith, which Muirhead and Winter have 
succeeded in duplexing so as to constitute a quadruplex that 
practically works well. Other quadruplex systems have been 
in use, since 1874, on sixty lines of the Western Union Tele¬ 
graph Co. in the United States. In France and England, great 
efforts have been made to keep abreast of the Americans in the 
rapid progress they are making in such applications of 
electricity. 
Accessory Apparatus. —This kind of apparatus is required at 
all telegraph offices ; but we cannot here give an account of it 
all. The line wires usually reach the office through a dis¬ 
tributor or commutator, like those shown in fig. 184. This 
commutator is made of strips of copper, crossing each other at 
right angles, and provided with a circular opening at their 
points of intersection, so that by inserting metallic pegs, p, a 
connection is made between the upper and lower strips. The 
pegs must fit in tightly, both above and below, to ensure the 
contacts. It will be understood that any one of the four line 
wires, L 1 , L 2 , L 3 , and L 4 , which reach the lower strips of our 
apparatus, can at will be connected with anyoneofthe linesthat 
proceed from the upper strips, A 1 , A 2 , A 3 , A 4 . Apparatus of this 
kind is also employed for connecting up the battery wires, and 
one of the binding screws is commonly kept for a wire that 
makes an earth connection. 
Earth Plates .—The wires that make the earth connections 
at telegraphic offices require some attention, for a bad connec¬ 
tion may cause much trouble. When the ground is damp, it is 
only necessary to bury in it a large metallic plate, to which a 
strand of iron wires from the office is attached. But if the 
soil be very dry, the earth connection must be made in a well 
or neighbouring stream. There are instances in which it has 
been found necessary to carry the earth wire a great distance 
