rchandise.

_Silk from Spiders._

At the last Anniversary of the Society of Arts, the Silver Isis Medal
was presented to Mr. D.B. Rolt for obtaining Silk from the Garden
Spider. We find the details in the volume of the Society's
_Transactions_ lately published.

"The subject of Mr. Rolt's experiments has been the garden spider,
Aranea diadema, the webs of which, in autumn, are so conspicuous on the
surface of shrubs and in other similar situations. On allowing one of
these animals to crawl over his hand, he found that it drew a thread
with it wherever it went: he likewise, without any difficulty, wound
some of this thread over his hand, finding that the spider continued
spinning while the thread was winding up.

"On this hint, he connected a small reel with the steam-engine of the
factory in which he is occupied, and putting it in motion, at the rate
of 150 feet per minute, found that the spider would thus continue to
afford an unbroken thread during from three to five minutes. The
specimen of this silk, which accompanies Mr. Rolt's communication, was
wound off from twenty-four spiders in about two hours. Mr. R. estimates
its length at 18,000 feet; its colour is white, and its lustre is
brilliant, and completely metallic, owing, probably, to its great
opacity. No attempt has been made by him to combine two or more
filaments into one by winding, nor, of course, to form it into thread by
throwing.

"The thread of the garden spider is so much finer than that of the
silk-worm, that the united strength of five of the former is, according
to Mr. Rolt, equal only to one of the latter; and, assuming that the
weight is in proportion to the strength, and that a spider will yield
twice a-year a thread 750 feet long, while that produced by a single
silk-worm is 1,900 feet, it follows that the produce of one silk-worm is
equal to that of 6.3 spiders. Now, as on an average it takes about 3,500
silk-worms to produce a pound of silk, it would take about 22,000
spiders to produce an equal quantity. Besides, spiders are not so easily
confined as silk-worms, and whenever two come in contact, a battle
ensues, which ends in the destruction of the weaker one. Spiders kept
for silk must, therefore, be each in separate dens or cells; and the
apparatus contrived by Mr. Rolt for this purpose, although very
ingenious and well adapted to carry on a course of experiments with a
hundred or two, would manifestly be wholly inapplicable to any pu