le, 'On the Conversion of Dynamic into
Electrical Force without the use of Permanent Magnetism.' [Footnote: A
paper on the same subject, by Dr. Werner Siemens, was read on January
17, 1867, before the Academy of Sciences in Berlin. In a letter to
'Engineering,' No. 622, p. 45, Mr. Robert Sabine states that
Professor Wheatstone's machines were constructed by Mr. Stroh in the
months of July and August, 1866. I do not doubt Mr. Sabine's
statement; still it would be dangerous in the highest degree to depart
from the canon, in asserting which Faraday was specially strenuous,
that the date of a discovery is the date of its publication. Towards
the end of December, 1866, Mr. Alfred Varley' also lodged a
provisional specification (which, I believe, is a sealed document)
embodying the principles of the dynamo-electric machine, but some
years elapsed before he made anything public. His brother, Mr.
Cromwell varlet', when writing on this subject in 1867, does not
mention him (Proc. Roy. Soc, March 14, 1867). It probably marks a
national trait, that sealed communications, though allowed in France,
have never been recognised by the scientific societies of England.] On
the 14th of February a paper from Sir Charles Wheatstone was received,
bearing the title, 'On the Augmentation of the Power of a Magnet by
the reaction thereon of Currents induced by the Magnet itself.' Both
papers, which dealt with the same discovery, and which were
illustrated by experiments, were read upon the same night, viz. the
14th of February. It would be difficult to find in the whole field of
science a more beautiful example of the interaction of natural forces
than that set forth in these two papers. You can hardly find a bit of
iron--you can hardly pick up an old horse-shoe, for example--that does
not possess a trace of permanent magnetism; and from such a small
beginning Siemens and Wheatstone have taught us to rise by a series of
interactions between magnet and armature to a magnetic intensity
previously unapproached. Conceive the Siemens armature placed between
the poles of a suitable electro-magnet. Suppose this latter to possess
at starting the faintest, trace of magnetism; when the armature
rotates, currents of infinitesimal strength are generated in its coil.
Let the ends of that coil be connected with the wire surrounding the
electro-magnet. The infinitesimal current generated in the armature
will then circulate round the magnet, augmentin