106 
should be comparatively short and thick. Hence the incom- 
patibility of the armature and electro-magnetic circuits, 
when exalted dynamic effects, outside the machine, are 
required. 
It is not a little interesting to observe how, in the progress 
of physical science, the same train of reasoning is often 
pursued by several individuals having no communication 
with one another. In the present instance, it would appear 
that the “augmentation of the power of a magnet by 
induction currents produced thereby, and reacting upon the 
magnet itself,” has also suggested itself to other experi- 
mentalists besides M. Siemens and Dr. Wheatstone. In a 
letter published in The Engineer of July 20th, 1866, p. 42, 
the writer (Mr. J. Murray) says : — “ The description in recent 
numbers of The Engineer of Mr. Wilde’s admirable improve- 
ments in the magneto-electric machine, induces me to point 
out, if you will permit it through your columns, a variety 
of the principles embodied in his machine, which is so 
obvious that it cannot fail to be hit upon by some inventor 
before long.” 
It is briefly this : — Whereas Mr. Wilde, beginning with 
an ordinary magneto-electric machine, uses the current 
obtained from it to charge a powerful electro-magnet, and 
from this obtains a second and more powerful current, which, 
used in like manner, produces one still more intense, I, using 
only a single machine, pass the current obtained from its 
armatures through wires coiled round the permanent mag- 
nets, in such a direction as to intensify their magnetism, 
which, in its turn, reacts upon the armatures and intensifies 
the current. 
“ It is obvious that the amount of mechanical force which 
can thus be converted into electricity is only limited by the 
capacity of the iron for magnetism ; just as the power of a 
steam engine is only limited by the capacity of the boiler 
for absorbing heat.” 
