80 Velocity of the Galvanic Current in Telegraph Wires. 
made a series of experiments with this telegraph between Boston 
and New York.* But although the pass-time is here avoided, 
other sources of error are introduced. The timest of delay and 
of persistence in the chemical action take the place of the induc- 
tion and the eduction-times in the electro-magnet, and a new and 
serious difficulty presents itself in the spreading of the lines 
which have undergone chemical action. 
he character of the electro-chemical telegraph allows no lo- 
cal circuit, in the technical sense of this term, and indeed it is 
Pe Sperad b for a current capable of closing a local circuit would 
ce to act with energy on the very sensitive salt with which 
the paper is saturated. 
But in the experiment for velocity, it is indispensable that a 
record be kept at the two terminal stations, at least; and the 
closing of the circuit, in order to record at one sta ation, necessa- 
rily diverts the current from the other. With a powerful battery 
a record may be sqegessfally. net at stations no farther distant 
than New York and Boston; but if we use a line as long as that 
between New York and Buffalo, a battery so powerful as to burn 
a hole through the paper at one terminus, cannot record signals 
at the other, when the circuit of the signal- -station is closed. 
r. Bain has ingeniously remedied this difficulty by using @ 
aor circuit at the signal-station, which is closed by the same 
key that closes the main circuit. Yet even this introduces still 
a new source of uncertainty. A curious result which Mr, Walker 
has deduced{ from his experiments consists in the fact that the 
discolored lines, which measure the duration of the current, are — 
perior intensity of the current, and consequently, of its chemical 
action at the signal-station. The question remains open for dis- 
ssion. 
The experiments of Fizean and Gounelle, in France, de- 
scribed in the Comptes Rendus for April last, were on an 
entirely different principle, and conducted them to a series of in- 
ferences which they give in detail. The published description $ 
of their method is very obscure, and the data on which their in- 
ferences are founded are not fully given. Their method appears — 
to be in some degree, analogous to the very elegant rt 
* Ast. Journ, i, p. 105. 
f Ase Jou - Assoc, 1849, p-. 189. Ast. Journ, i, p. ai eae 
ourn., i, Comptes Rendus, xxx, p. 
Comptes elie: 90, 132. : = 
