Velocity of the Galvanic Current in Telegraph Wires. 77 
If we assume the intensity of the attraction exerted by the 
magnet on the armature to be equal to gravity at the earth’s sur- 
face,—the following numbers give the pass-time for different 
“-* %.: : . 
lengths of the pass. 
seem of at Time. Length of Pass. Time. 
Millimeters. Seconds. Millimeters. _ Seconds. 
2° 0:0226 
2°25 0214 1-00 0143 
2:00 0202 0-75 0124 
175 0189 0:50 “0105 
1-50 0175 0:25 0-0086 
As far as T can judge, the usual pass in the main-circuit re- 
ceiving magnet is between 1™™75 and 0™™50, which would on 
our present assumption, give the pass-time 0-019 and 0010. 
An attractive force four times that of gravity would give the half of 
these numbers. But this mode of viewing the subject is a very 
rough one, for as the attraction varies with the distance, the ini- 
a 
tial force, (which exercises the greatest influence upon the time 
of passage,) would be much less when the length of pass is 
greater,—and the tension of the back-spring also operates to 1n- 
crease the pass-time very considerably. I incline to the belief 
that the average pass-time in the experiments of Feb. 4, was 
about 0:03. Mr. Walker, on the contrary, estimates it at ;';th of 
a second—more than twice as much. Had we any means ot 
measuring the absolute duration of the interruption of the cireult 
y Mr. Saxton’s clock, it would be of great service in aiding us 
to deduce the pass-time in many cases. In all conclusions drawn 
from the telegraph fillets alone, the pass-time and the induction- 
time are inseparably combined. Denoting the several intervals 
by their initials, we have for the length of the recorded clock- 
pause, which we will indicate by a capital letter, C=¢e-e+t+p. 
As a first hypothesis, we may assume what appears not im- 
probable from other considerations, that e and @ are equal. Then 
subtracting the length of the interval during which the circuit 
axton expressed himself unable to do this, which is much to be 
Tt had appeared to me that careful observations of the 
angle with the vertical, made by the pendulum at the ume of 
; | f our hypothesis regard- 
ing the equality of the induction and eduction-times. This is 
wicgndad ca 
a 
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