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

DESCRIPTION OF THE SILK-WORM, 109
and consistent yellow ball ; the laborer, of course, always remaining
on the inside of the sphere which it is forming*.
The silken filament, which when drawn out appears to be
one thread, is composed of two fibres, unwound through the
two orifices before described ; and these fibres are brought to-
gether by means of two hooks, placed within the silk-worm's
mouth for the purpose. The worm rests on its lower extremity
throughout the unwinding operation, and employs its mouth
and front legs in the task of directing and uniting the two fila-
ments. The filament is not wound in regular concentric circles
round the interior surface of the ball, but in spots, going back-
wards and forwards with a sort of wavy motion.
This appa-
rently irregular manner of proceeding is plainly perceptible
when the silk is being reeled off the ball ; which does not make
more than one or two entire revolutions while ten or twelve
yards of silk are being transferred to the reelt.
At the end of the third or fourth day, the worm will have
completed its task ; and we have then a silk cocoon (See Fig-
ure 3. plate III.), with the worm imprisoned in its centre ; the
« If at this time any of the threads intended for the support of the cocoon
should be broken, the worm will find, in the progress of its work, that the ball,
not being properly poised, becomes unsteady, so that the insect is unable properly
to go forward with its labors. Under these circumstances the worm pierces and
altogether quits the unfinished cocoon, and throws out its remaining threads at
random wherever it passes ; by which means the silk is wholly lost, and the
worm, finding no place wherein to prepare for its change, dies without having
effected it. It may sometimes happen, but such a thing is of unfrequent occur-
rence, that the preparatory threads before mentioned are broken by another
worm working in the neighborhood, when the same unsatisfactory result will be
experienced.— 06s. on the Culture of Silk, by A. Stephenson.
t Mr. Robinet, of Paris, made the following curious calculation on the move- ')
ments a silk-worm must make in forming a cocoon supposed to contain a thread )
of 1500 metres. It is known, says Mr. Robinet, that the silk-worm, in forming /
his cocoon, does not spin the silken filament in concentric circles round the inte- (
rior surface of the ball, but in a zigzag manner. This it effects by the motions of (
its head. Now if each one of these motions gives half a centimetre of the silken
filament ; it follows that the worm must make_300,000 motions of its head to
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form it and if the labor requires 72 hours in the' performance, the creatiu-e
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makes 100,000 motions every 24 hours, 4,166 per hour, 69 per minute, and a lit^
tie more than one in a second !
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