Faraday as a Discoverer. 49 
terminal plates dipped into the earth, and su the wire to 
lie in the magnetic meridian. The ground underneath the 
wire is influenced like the wire itself by the earth’s rotation ; 
if a current from south to north be generated in the earth 
under the wire, a similar current from south to north would be 
generated in the earth under the wire; these currents would run 
against the same terminal plate, and thus neutralize each other. 
his inference appears inevitable, but his profound vision 
received its possible invalidity. He saw that it was at least 
possible that the difference of conducting power between the 
earth and the wire might give one an advantage over the other, 
and that thus a residual or differential current might be ob- 
tained. He combined wires of different materials, and caused 
them to act in pda to each other: but found the com- 
bination ineffectual. The more copious flow in the better con- 
and the severed ends connected with a ce No 
Obs no effect, moving water might. He therefore worked at 
ondon Bridge for three days during the ebb and flow of the 
tide, but without any satisfactory result, Still he urges, ‘“Theo- 
tic seems a necessary consequence, that where water 
is flowing there electric currents should be formed. If a line 
. be imagined passing from Dover to Calais through the sea, and 
returning through the land, beneath the water, to Dover, it 
traces out a circuit of conducting matter one part of which, 
when the water moves up or down the channel, is cutting the 
a curves of the earth, whilst the other is relatively at 
There is every reason to believe that currents 
ao run in the general direction of the circuit described, either 
one way or the ed Bee as the passage of the waters is | 
up or down the Cha This wa was written Etre the sub- 
marine cable was focal of, and he once informed me that 
actual observation upon that cable pee Yonn Toued to bem: 
accordance with his theoretic deduction. 
* I am indebted to a friend for the following exquisite morsel :—" A short t time 
after rag publication of Faraday's first researc’ arches in m: magnels-siec nee he attended 
Meeting of the British Association at Oxford, i in 1832.—On this occasion he w 
requested by some of the authorities to repeat the celebrated ipeiee ie eliciti 
a spark from a magnet, employing for this purpose the sa ma ~ in 
molsan Museum, a this he Seeene aya hg Ue eat assemble 
