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

148 CULTIVATION AND MANUFACTURE OF SILK.
SO, to that with which the air moved, as was apparent from
observations made on the motion of detached Hnes similarly
exposed. The spiders, in the next place, carefully ascertained
whether their lines had become firmly attached to any object
or not, by pulling at them with the front pair of legs : and if
the residt was satisfactory, after tightening them sufficiently,
they made them pass to the twig ; then discharging from their
spinners, which they applied to the spot where they stood, a
httle more of their hquid gum, and committing themselves to
these bridges of their own constructing, they passed over them
in safety, drawing a second line after them, as a security in case
the first gave way, and so effected their escape.
' Such was invariably the result when spiders were placed
where the air was liable to be sensibly agitated : I resolved, there-
fore, to put a bell-glass over them ;
and in this situation they re-
mained seventeen days, evidently unable to produce a single
line by which they could C}uit the branch they occupied, with-
out encomitering the water at its base ; though, on the removal
of the glass, they regained their liberty with as much celerity
as in the instances already recorded.
' This experiment, which, from want of due precaution, has
misled so many distinguished naturalists, I have tried with several
geometric spiders, and always with the same success*.' "
Mr. Blackwall, from subsequent experiments, says he is
" confident in affirming, that in motionless air, spiders have not
the power of darting their threads even through the space of
half an incht." The following details are given in confirma-
tion of this opinion. Mr. Blackwall observed, the 1st of Oct.,
1826, a httle before noon, with the sun shining brightly, no
wind stirring, and the thermometer in the shade ranging from
55°. 5 to 64°, a profusion of shining lines crossing each other at
every angle, forming a confused net-work, covering the fields
and hedges, and thickly coating his feet and ankles, as he
walked across a pasture. He was more struck with the phenomenon
because on the previous day a strong gale of wind had
blown from the south, and as gossamer is only seen in calm
* Linn. Trans., vol. xv. p. 456. t Mag. Nat. Hist., vol. ii. p. 397.