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ADDRESS OF PROFESSOR LOVERING. 619 
When Wheatstone devised and executed the ingenious experi- 
ment of producing three electrical sparks, not strictly at the same 
instant, but after the brief interval required by electricity to travel 
over one quarter of a mile of copper wire, and then of observing, not 
the sparks themselves, but their images, as seen in a mirror re- 
volving with the prodigious velocity of 800 turns in a single second, 
and from the prolongation and relative displacement of these 
images deducing the velocity of electricity, the duration of the 
electrical light, and the duality in the direction of the transmitted 
disturbance, he delighted the brotherhood of science by the skill 
and boldness of his attempt and astonished it by the extravagance 
of his results. For twenty years no one ventured to repeat the 
difficult experiment. When at length it was tried by Feddersen, 
and more recently by our own associate, Rood, the values which 
they assigned to the duration of the electrical light, and which could 
not be challenged, made still the wonder grow. So far as this 
mode of experimenting concerns the velocity of electricity, Wheat- 
stone stands alone: and his estimate of this velocity (the largest 
known Velocity in the universe unless we count in the velocity of 
stavitation) has never been brought to a second trial. Indirectly, 
ìt has been tested by some of the operations conducted upon land 
and ocean lines of telegraph. When the local times of two places 
ate compared by means of electro-magnetic signals, sent alter- 
nately in Opposite directions, the difference of longitude and the 
tansmission-time of electricity can be disentangled from one an- 
other, by the strategy of mathematics, and the most probable value 
Computed for each. The velocity which has been calculated from 
these longitude-campaigns falls far below that credited to Wheat- 
ears The apparent discrepancy is explained by a misinterpre- 
tation of Wheatstone’s experiment. An experiment which proves 
~ electricity runs through one quarter of a mile of wire at the 
Mior 288,000 miles a second does not justify the inference that 
would move over. 288,000 miles in one second. Anomalous as 
de may be, electricity has no velocity in the ordinary sense. 
to transmission time of the electrical disturbance is proportioned 
the square of the distance to be travelled. Therefore, the 
| a y has no constant fixed value, but varies with the length of 
a amey. This law, which is deduced from the mathematical 
ty of Ohm, introduces order among the experiments where, 
Stherwise, there would be chaos. It is not surprising that Wheat- 
