magnet to and from the helix, or the helix to and from the magnet, currents
were produced indicated by the galvanometer.

1725. The thick copper plate (1721.) was afterwards interposed between the
magnetic pole and the helix; nevertheless on moving these to and fro,
effects, exactly the same in direction and amount, were obtained as if the
copper had not been there. So also on introducing a plate of sulphur into
the interval, not the least influence on the currents produced by motion of
the magnet or coils could be obtained.

1726. These results, with many others which I have not thought it needful
to describe, would lead to the conclusion that (judging by the _amount_ of
effect produced at a distance by forces transverse to the electric current,
i.e. magnetic forces,) the intervening matter, and therefore the
intervening particles, have nothing to do with the phenomena; or in other
words, that though the inductive force of static electricity is transmitted
to a distance by the action of the intermediate particles (1164. 1666.),
the transverse inductive force of currents, which can also act at a
distance, is not transmitted by the intermediate particles in a similar
way.

1727. It is however very evident that such a conclusion cannot be
considered as proved. Thus when the metal copper is between the pole and
the helix (1715. 1719. 1725.) or between the two helices (1721.) we know
that its particles are affected, and can by proper arrangements make their
peculiar state for the time very evident by the production of either
electrical or magnetical effects. It seems impossible to consider this
effect on the particles of the intervening matter as independent of that
produced by the inductric coil or magnet C, on the inducteous coil or core
A (1715. 1721.); for since the inducteous body is equally affected by the
inductric body whether these intervening and affected particles of copper
are present or not (1723. 1725.), such a supposition would imply that the
particles so affected had no reaction back on the original inductric
forces. The more reasonable conclusion, as it appears to me, is, to
consider these affected particles as efficient in continuing the action
onwards from the inductric to the inducteous body, and by this very
communication producing the effect of _no loss_ of induced power at the
latter.

1728. But then it may be asked what is the relation of the particles of
insulating bodies, such as air, sulphur,