I5ETV ELECTRIC LIGHT IN WESTMINSTER CLOCK TOWER. 267 
nets, with, similar poles joined together. In Pixii's apparatus, 
which was invented about the time of these Grottingen experi- 
ments the magnet rotated before the coil. Later on, Saxton and 
Clarke improved upon this by fixing the magnet, and causing 
the double bobbin, which is much lighter, to rotate before it. 
Attention was now drawn to the production of copious magneto- 
ciurents. A new impetus was given; a great question was 
proposed, and a solution required. Grenius and skill went to 
work, and it was not until several years had elapsed that the 
knot was severed. One of the most ardent and successful in- 
vestigators of this subject was Professor Holmes. He struggled 
against difficulties and prejudices, and had at last the satisfac- 
tion of exalting the tiny spark of Faraday into a brilliant star,^ 
and of giving to our coasts beacon-lights whose vivid flashes 
may be distinguished far out at sea by the storm-beaten 
mariner. 
Mr. Wilde combined all valuable anterior facts and principles 
into a machine of unprecedented power. He rejected the coils 
of Clarke, and adopted the armature of Siemens, in which tha 
transversal was replaced by the longitudinal system of winding 
the wires around the iron cores. The current from the upper 
armature, which revolved between the poles of permanent mag- 
nets, was transmitted round large electro-magnets, which, by 
their action on a second armature, produced the useful current. 
The mutual action principle was the next valuable discovery 
in magneto-electricity. It seems to have occurred simultaneously 
to Siemens and Wheatstone, and consists in building up a 
powerful magazine from the very small amount of magnetism 
that remains in soft-iron when once a galvanic current has 
been sent round it. This beautiful principle was embodied by 
Ladd in his apparatus, to which a silver medal was awarded at 
the Paris exhibition of 1867. 
However satisfactory were the effects obtained from all these 
machines, there was yet room for several improvements. The 
currents were instantaneous in duration, and alternately in 
opposite directions. This made no material difference in the 
production of electric light ; but in electro-metallurgy it required 
a commutator, which is not always a convenient appendage. 
These imperfections were finally removed by the Grramme ma- 
chine, in which we have absolutely continuous currents, and all 
in the same direction. This invention is thus among the most 
important of this prolific age ; it marks a new era in the annals 
of science. 
We have already stated that its introduction into this country 
is due to the diligence and enterprise of M. Werdermann ; and 
Michael Faraday,” by Dr. Gladstone. 
