| Velocity of the Galvanic Current in Telegraph Wires. 155 
o : removed from the part of the circuit between the clock and the 
“oe ground, and interposed between the clock and Pittsburg. 
umber of measurements used to obtain the mean differ- 
ence of the registers is so large that the addition or subtraction 
of fifty consecutive measurements exerts no appreciable influence 
on the result. : 
a __ We have seen that when the clock-pauses are made at Wash- 
TS ington and the arbitrary signal-pauses at St. Louis, the diflerence 
of the interval between the pauses on the registers of the stations 
corresponds to the time occupied by the current in traversing 
twice the distance between the stations,—the clock-pauses being 
e is) 
a by the same amount. T me is true of intermediate places, 
a. the excess of the recorded interval at the clock-station being 
a. greater by an amount equal to twice the distance between the 
oe Stations whose fillets are compared, divided by the number of 
.* miles traversed by the voltaic current in a second. 
Let us now consider the effect of a signal not made at a ter- 
_ Ininal station, but at some intermediate one. For all places be- 
yond this, the two pauses occur later than the corresponding one 
and its record should be identical with that of the signal-station 
itself. We are thus enabled to control our estimate of the veloc- 
ity between the clock and the signal station, by the records made 
at all the stations beyond. 
I find the following to be the mean excesses of the intervals 
between the signal-pauses and the preceding clock-pauses on the 
Washington fillet, over those on the fillets at the other stations. 
Washington Excesses. 
ee Te  —e 
Signals. cee 
Be a 0 a a 
00295 00983. | +«0-0378 00451 
0317 0752 0843 0950 
* 03847 ‘0750 | 1163 1343 
0455 0704 bs S108 1451 
ee. 
___ Confining ourselves at first to the records of the signals made 
at St. Louis, we find the several registers to indicate the follow- 
ocities : 
. _ 12772 miles in a second. 
. 18096. “ 
' 11124 e 
14404 - 
