258 
THE TELEGRAPH, 
In fig. 182 is shown the arrangement of the apparatus used 
at Marseilles for duplexing the cable between Marseilles and 
Malta. This cable is the simpler example of balance as 
obtained by the Muirhead system. From Marseilles the cable, 
which is 826 nautical miles in length, traverses the Mediter¬ 
ranean to Bona, before proceeding eastward to Malta. The 
system consists in a Wheatstone’s bridge combined with an 
artificial cable in which many of the inducing layers are 
omitted, the conductor of the artificial line passing to earth 
through a resistance of 7,000 ohms. 
For the cable between Aden and Bombay, which is 1,817 
nautical miles long, the balance is established at Aden with 
5 = 1*28 microfarad, r = 0 , r 2 = o, r 3 = 210,000 at a point in the 
artificial cable answering 
to a distance of 250 miles 
from Aden ;r 4 andr 5 = infi¬ 
nity. The proportion of 
the artificial to the real 
line is as three to four, and 
the resistances of the arms 
of the balance are respec¬ 
tively 2,000 and 2,080. 
The total resistance of the 
real line is 11,827 ohms, 
and its capacity 656 micro¬ 
farads. 
These two cables work with a Thomson’s siphon recorder, 
the delicacy of which enables the balance to be made with 
more readiness than the mirror galvanometer. The rapid 
succession of currents gives rise to slow oscillations as the 
waves of electricity are formed in the line, and superimposed 
on these are the set of individual signals in the form of 
greater oscillations. The coil of the recorder is less sensitive 
than the galvanometer mirror to these undulations, and con¬ 
sequently the zero of the recorder is less easily affected than 
that of the galvanometer. In.the mirror the displacement of 
the zero is apt to be mistaken for signals, because the luminous 
spot travels in the same straight line right and left, whilst the 
displacement of the zero of the recorder is transverse to the 
line of signals. More than this, the mirror signals are 
