Recent Advances in Telegraphy. 
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said, however, that the more nearly the model cable is made 
to equal the real one, the less needful is any other help. 
The use of such additional devices is, as we have said, to 
counteract the “ kick,” or false signal, on the receiving in- 
strument, due to a want of perfect accord in the balance 
between the real and artificial lines. Thus it will be seen 
by a reference to Fig. 4 that if there is any difference be- 
tween the rush of electricity into the cable at c and the 
rush into the artificial line at d, a momentary pulse will 
traverse the receiving instrument and jerk the needle ; this 
will take place at every signal sent from the station. The 
needle thus “ kicked ” by the home sending is of course 
unable to deliver the message from the distant station. It 
is comparatively easy to get rid of the violence of the kick 
and to reduce it to a slight jar or tremor, but it is a diffi- 
cult matter to eliminate it altogether. This, however, has 
been practically achieved by Muirhead’s system. 
The principal device for obviating the “ kick ” is to coun- 
teract its effeCt on the instrument by superposing an 
equal “ kick ” in the opposite direction. This can be done 
by allowing a battery-current to flow for an instant through 
an extra coil of the receiving instrument. But it is gene- 
rally effected either- — 
By connecting a condenser to the instrument, so that a 
sudden induCtive charge into it shall produce the kick 
required ; or — 
By using a “ secondary battery ” (made of a series of 
plates of lead or of platinum in a weak solution of 
sulphuric acid) in the same way as the condenser ; or — 
By employing an induCtion-coil and placing the primary 
in circuit, somewhere, with the signalling-current, while 
the secondary is connected to the receiving instrument ; 
so that the sudden induced currents generated in it by 
each signal-current may produce a “ counterfeit kick ” 
in the opposite direction to the real one, and so com- 
pletely neutralise it. 
But although these plans of neutralising the kick by an 
equal and opposite one are doubtless serviceable, they intro- 
duce complications into the balance which are to be avoided, 
if possible, in practice. By the use of the induCtive-resist- 
ances, and a simple but effectual adjustment which is 
applied to them, the kick is practically reduced to nil, and 
a perfect balance obtained, so that constant sending in op- 
posite directions can go on simultaneously with signals as 
beautiful as in the ordinary method of working. 
