must often occur together. A large polished fragment of amber
or jet attracts indeed, even without friction, but less strongly; but if it
be brought gently near a flame or a live coal, so that it equally becomes
warm, it does not attract small bodies because* it is enveloped in a cloud
from the body of the flaming substance, which emits a hot breath, and then
impinges upon it vapour from a foreign body which for the most part is at
variance with the nature of amber. Moreover the spirit of the amber which
is called forth is enfeebled by alien heat; wherefore it ought not to have
heat excepting that produced by motion only and friction, and, as it were,
its own, not sent into it by other bodies. For as the igneous heat emitted
from any burning substance cannot be so used that electricks may acquire
their force from it; so also heat from the solar rays does not fit an
electrick by the loosening of its* right material, because it dissipates
rather and consumes it (albeit a body which has been rubbed retains its
virtue longer exposed to the rays of the sun than in the shade; because in
the shade the effluvia are condensed to a greater degree and more quickly).
Then again the fervour from the light of the Sun aroused by means of a*
burning mirror confers no vigour on the heated amber[136]; indeed it
dissipates and corrupts all the electrick effluvia. Again, burning* sulphur
and hard wax, made from shell-lac, when aflame do not allure; for heat from
friction resolves bodies into effluvia, which flame consumes away. For it
is impossible for solid electricks to be resolved into their own true
effluvia otherwise than by attrition, save {54} in the case of certain
substances which by reason of innate vigour emit effluvia constantly. They
are rubbed with bodies which do not befoul their surface, and which produce
a polish, as pretty stiff silk or a rough wool rag which is as little
soiled as possible, or the dry palm. Amber also is rubbed with amber, with
diamond, and with glass, and numerous other substances. Thus are electricks
manipulated. These things being so, what is it which moves? Is it the body
itself, inclosed within its own circumference? Or is it something
imperceptible to us, which flows out from the substance into the ambient
air? Somewhat as Plutarch opines, saying in his _Quaestiones
Platonicae_[137]: That there is in amber something flammable or something
having the nature of breath, and this by the attrition of the su