The history of silk, cotton, linen, wool, and other fibrous ... - Cd3wd.com

146 CULTIVATION AND MANUFACTURE OF SILK.
must be a mere fancy ; at least it is not countenanced by any-
thing which we have observed.
4. An opinion mucli more recondite is mentioned, if it was
not started, by M. D'Isjonval, that the floating of the spider's
thread is electrical. " Frogs, cats, and other animals," he says,
'• are afiected by natural electricity, and feel the change of wea-
ther ; but no other animal more than myself and spiders." In
wet and windy weather he accordingly found that they spun
very short lines, " but when a spider sjrins a long thread,
there is a certainty of fine weather for at least ten or twelve
days afterxoards*P A periodical writer, who signs himself
Carolant, fancies that in darting out her thread the spider emits
a stream of air, or some subtle electric fluid, by which she
guides it as if by magic.
A living writer (Mr. John Murray) whose learning and skill
in conducting experiments give no little weight to his opinions,
has carried these views considerably farther.
" The aeronautic
spider," he says, " can propel its thread both horizontally and
vertically, and at all relative angles, in motionless air and in
an atmosphere agitated by winds ; nay more, the aerial trav-
eller can even dart its thread, to use a nautical phrase, in the
' wind's eye.' My opinion and observations are based on many
hundred experiments The entire phenomena are
electrical. When a thread is propelled in a vertical plane, it
remains perpendicular to the horizontal plane always upright,
and when others are projected at angles more or less inclined,
their direction is invariably preserved ; the threads never inter-
mingle, and when a pencil of threads is propelled, it ever pre-
sents the appearance of a divergent brush. These are elec-
trical phenomena, and cannot be explained but on electrical
principles."
" In clear, fine weather, the air is invarial)ly positive ; and it
is precisely in such weather that the aeronautic spider makes
its ascent most easily and rapidl}^, whether it be in summer or
winter." " When the air is weakly positive, the ascent of the
* Brez, Flore des Insectophilcs. Notes, Supp. p. 134.
t Thomson's Ann. of Philosophy, vol. iii. p. 306.