74 Velocity of the Galvanic Current in Telegraph Wires. 
the electrotome and electropm@a readings.* For my own part, I 
prefer to use the electrotomes alone. 
The only signal that can be made in a closed circuit is of course 
an electrotome. We break the circuit by tapping on the key. As_ 
soon as the finger is removed, the circuit is closed again by a 
spring, and an electropcea signal thus made. Do these two sig- 
nals travel with the same velocity? If they do not, the clock- 
pauses must increase or diminish in length, as they are successive- 
ly recorded at more remote stations. 'They must become elon- 
gated if the electrotome signal travel the faster, and contracted if 
the contrary. ‘This question is an important one, but its diseus- 
sion may be postponed for a while, as the length of the recorded 
pause is dependent on many other circumstances, and especially 
on the adjustments of the registering apparatus, which are not 
nly very different at different stations, but appear to have been : 
continually changed at the same station during the evening by. 
the telegraph operators in charge of the registers. As far as I feel 
warranted in forming an opinion, I incline to the belief that these 
two kinds of signals traverse the circuit with equal speed,—or, to 
express the same idea in a different form, that induction of the 
electrical state in the successive molecules of the conducting me- 
dium, requires neither more nor less time than that required for a 
molecule to be restored to a condition of entire electrical equilib- 
rium. The better to fix one’s ideas in thinking on the subject, 
some hypothesis is desirable, which shall be capable of explaining 
all the phenomena; and I have accustomed myself to consider the 
propagation of electric polarity through a medium, as taking 
placey by the inductive force exerted upon each successive mole- 
cule{ by the adjacent one. 
_We consider the telegraph-wires as composed of a series of 
contiguous elements, an electrotome taking place at any point 
puts an end to the state of electrical tension in the nearest ele- 
ment on each side. The electrical equilibrium being restored in 
these elements, no force exists$ to continue the disturbance in the 
succeeding ones, and soon. An analogy to the propagation of 
an electropa, or electric perturbation, may be drawn from the 
known lawsof magnetism. If we have a curved rod of soft iron 
forming a little less than an entire circumference, and fill the gap 
witha bit of magnetic iron, the whole circle becomes magnetic. 
Although the period required for the transmission of this force is 
so short as to defy all attempts to measure it, there can be no 
doubt that a finite time intervenes between the introduction of 
the magnet and the magnetization of the most remote part of the — 
al 
4 
Faraday, Researches, i, § 1677. 
* Proc. Am. Phil. Soc, vy, p. 76. Astr. Nachr., ete 56. 
rad Ibid, § 1700. 
Ibid, i, $$ 1671, 1686. : : 
