the oxygen
in crystallized proto-sulphate of iron, or 3.4 times its weight of
metallic iron in that state of combination.' By its capability to
deflect a fine glass fibre, he finds that the attraction of this bulb
of oxygen, containing only 0.117 of a grain of the gas, at an average
distance of more than an inch from the magnetic axis, is about equal to
the gravitating force of the same amount of oxygen as expressed by its
weight.

These facts could not rest for an instant in the mind of Faraday without
receiving that expansion to which I have already referred. 'It is hardly
necessary,' he writes, 'for me to say here that this oxygen cannot exist
in the atmosphere exerting such a remarkable and high amount of magnetic
force, without having a most important influence on the disposition of
the magnetism of the earth, as a planet; especially if it be remembered
that its magnetic condition is greatly altered by variations of its
density and by variations of its temperature. I think I see here the
real cause of many of the variations of that force, which have been, and
are now so carefully watched on different parts of the surface of the
globe. The daily variation, and the annual variation, both seem likely
to come under it; also very many of the irregular continual variations,
which the photographic process of record renders so beautifully
manifest. If such expectations be confirmed, and the influence of the
atmosphere be found able to produce results like these, then we shall
probably find a new relation between the aurora borealis and the
magnetism of the earth, namely, a relation established, more or less,
through the air itself in connection with the space above it; and even
magnetic relations and variations, which are not as yet suspected,
may be suggested and rendered manifest and measurable, in the further
development of what I will venture to call Atmospheric Magnetism. I may
be over-sanguine in these expectations, but as yet I am sustained in
them by the apparent reality, simplicity, and sufficiency of the
cause assumed, as it at present appears to my mind. As soon as I
have submitted these views to a close consideration, and the test of
accordance with observation, and, where applicable, with experiments
also, I will do myself the honour to bring them before the Royal
Society.'

Two elaborate memoirs are then devoted to the subject of Atmospheric
Magnetism; the first sent to the Royal Society on the 9th of Octo