The cultivation of certain species of spiders solely for the
fine threads which they weave has an important bearing upon the
work of the astronomer.
No substitute for the spider’s thread has yet been found for
bisecting the screw of the micrometer used for determining the
positions and motions of the stars; not only because of the
remarkable fineness of the threads, but because of their durable
qualities.
The threads of certain spiders raised for astronomical purposes
withstand changes in temperature, so that often in measuring
sunspots they are uninjured when the heat is so great that the
lenses of the micrometer eye-pieces are cracked. These spider
lines are only one-fifth to one-seventh of a thousandth of
an inch in diameter, compared with which the threads of the
silk-worm are large and clumsy.--_Harper’s Weekly._
(2154)
=Nature Altruistic=--See ALTRUISM IN NATURE.
=Nature and Man=--See STRUGGLE.
=Nature and Prayer=--See PRAYER AND THE BODY; PRAYER ANSWERED.