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

SILKEN MATERIAL OF THE SPIDER. 147
spider will be difficult, and its altitude extremely limited, and
ihe threads propelled will be but little elevated above the hori-
zontal plane. When negative electricity prevails, as in cloudy
weather, or on the approach of rain, and the index of De
Saussure's hygrometer rapidly advancing towards humidity, the
spider is unable to ascend*."
Mr. Murray tells us, that " when a stick of excited sealing-
w^ax is brought near the thread of suspension, it is evidently
repelled ; consequently, the electricity of the thread is of a
negative character," while " an excited glass tube brought near,
seemed to attract the thread, and with it the aeronautic
spidert."
His friend, Mr. Bowman, further describes the aerial
spider as " shooting out four or five, often six or eight, extreme-
ly fine webs several yards long, which waved in the breeze, di-
verging from each other Ukc a pencil of rays." One of them
" had two distinct and widely diverging fasciculi of w^ebs," and
" a line uniting them w^ould have been at right angles to the
direction of the breezet."
'• Such is the chief evidence in support of the electrical the-
ory," says Mr. Rennie ; " but though we have tried these ex-
periments, we have not succeeded in verifying any one of them.
The following statements of Mr. Blackwall come nearer our
own observations.
5. ' Having procured a small branched twig,' says Mr.
BlackwaU, '
I fixed it upright in an earthen vessel containing
water, its base being immersed in the liquid, and upon it I
placed several of the spiders which produce gossamer. When-
ever the insects thus circumstanced were exposed to a current
of air, either naturally or artificially produced, they directly
turned the thorax towards the quarter whence it came, even
when it was so sUght as scarcely to be perceptible, and eleva-
ting the abdomen, they emitted from their spinners a small por-
tion of glutinous matter, which was instantly carried out in a
Une, consisting of four finer ones, with a velocity equal, or nearly
* Loudon's Mag. of Nat. Hist., vol. i. p. 322.
t Experim. Researches in Nat. Hist., p. 136
t Mag. Nat. Hist. vol. i. p. 324.