] a wet rim. A B is the
surface of the water; C D two rods, which stand up wet above the water; it
is manifest that the surface of the water is raised at C and D along with
the rods; and therefore the rod C, by reason of the water standing up
(which seeks its level and unity), moves with the water to D. On E, on the
other hand, a wet rod, the water also rises; but on the dry rod F the
surface is depressed; and as it drives to depress also the wave rising on E
in its neighbourhood, the higher wave at E turns away from F[141]; for it
does not suffer itself to be depressed. All electrical attraction occurs
through an intervening humour; so it is by reason of humour that all things
mutually come together; fluids indeed and aqueous bodies on the surface of
water, but concreted things, if they have been resolved into vapour, in
air;--in air indeed, the effluvium of electricks being very rare, that it
may the better permeate the medium and not impel it by its motion; for if
that effluvium had been thick, as that of air, or of the winds, or of
saltpetre burnt by fire, as the thick and foul effluvia given out with very
great force, from other bodies, or air set free from humour by heat rushing
out through a pipe (in the instrument of Hero of Alexandria, described in
his {59} book _Spiritalia_), then the effluvium would drive everything
away, not allure it. But those rarer effluvia take hold of bodies and
embrace them as if with arms extended, with the electricks to which they
are united; and they are drawn to the source, the effluvia increasing in
strength with the proximity. But what is that effluvium from crystal,
glass, and diamond, since these are bodies of considerable hardness and
firmly concreted? In order that such an effluvium should be produced, there
is no need of any marked or perceptible flux[142] of the substance; nor is
it necessary that the electrick should be abraded, or worn away, or
deformed. Some odoriferous substances are fragrant for many years, exhaling
continually, yet are not quickly consumed. Cypress wood as long as it is
sound, and it lasts a very long time indeed, is redolent; as many learned
men attest from experience. Such an electrick only for a moment, when
stimulated by friction, emits powers far more subtile and more fine beyond
all odours; yet sometimes amber, jet, sulphur, when they are somewhat
easily let free into vapour, also pour out at the same time an odour; and
on this account they allure