110 NOTICES OF THE MEETINGS [Jan. 30, 
bars of soft iron, with proper contrivances to prevent the interfering 
influence of the residuary magnetism which in such cases is more 
or less retained by the iron core of the coil. Another form of this 
application of electro-magnetism as a motive power consists in so 
arranging the electro-magnets that the poles may be alternately 
inverted, and so made to act upon adjacent permanent bar-magnets, 
both attractively and repulsively: these forms of the apparatus 
were also exhibited. 
Mr. Brande then stated that upon examining Mr. Shepherd’s 
electro-magnetic clocks at the Great Exhibition in Hyde Park, he 
had been especially struck by the excellent illustration which they 
afforded of the exclusive use of electro-magnetism as their moving 
power, its force being employed to give impulse to the pendulum, 
to propel the ordinary movement of the clock, and to effect the 
striking of the hour; no auxiliary weights or springs being in any 
case employed : and thinking the whole subject worthy the attention 
of the Members of the Royal Institution, had determined to bring 
it before them at one of their Friday Evening Meetings. He had 
therefore applied to Mr. Shepherd for such information and assis- 
tance as he required, and this had not only been cheerfully, but 
liberally given, Mr. Shepherd having furnished him with the 
pendulums, clocks, models, and diagrams, then before them, and 
with much useful information in reference to the whole subject. 
Mr. Brande first explained the mechanism of the pendulum, 
which is so arranged as to make and break an electric circuit, and 
consequently to make and unmake a horse-shoe magnet at each 
vibration. Each time that the magnet is made it attracts its 
armature, which lifts certain levers: one of these is concerned in 
raising a weighted lever and causing it to be held up by a latch 
or detent; the magnet is then unmade in consequence of the 
pendulum breaking the circuit, and the armature is released, when 
the pendulum lifts the latch, and allows the weighted lever to 
fall, which, in falling, strikes the pendulum so as to give it an 
adequate impulse: then the circuit is again completed, the armature 
attracted, the levers moved, the weight raised, and held up by the 
detent; another vibration breaks the circuit and releases the arma- 
ture; the pendulum then raises the detent, the weight falls, and 
in falling its arm strikes the pendulum, and gives it an impulse ; and 
so on. 
But the pendulum at each vibration not only makes and breaks the 
electric circuit of the battery which maintains its own action, but 
also, and simultaneously, that of a second battery, of which the duty 
is to make and unmake the electro-magnets belonging exclusively to 
the clock or clocks, which are upon this circuit. These electro- 
magnets act upon the extremes of one or more horizontal bar-magnets, 
so as alternately to attract and repel their opposed poles, and which 
carry upon their axis the pallets, by the alternating motion of which 
to the right and the left, the ratchet wheel is propelled onwards at 
