Page:Popular Science Monthly Volume 37.djvu/52

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THE POPULAR SCIENCE MONTHLY.

An illustration of the remarkable strength and elasticity of the foundation lines of orb-webs appears in a biographical notice of the distinguished astronomer, the late General Ormsby M. Mitchell, PSM V37 D052 Sector of a dew laden orb web.jpgFig. 1.—Sector of a Dew-laden Orb-web. (Magnified.) printed with an edition of his lectures. Prof. Mitchell directed his great ingenuity to the problem of causing a clock to record its beats telegraphically, and at the same time perfectly perform the work of a time-keeper. The required makes and breaks in the battery were effected by means of a cross of delicate wire and a mercury-cup. Many obstacles having been overcome, there arose the great difficulty of procuring a fiber sufficiently minute and elastic to constitute the physical union between the top stem of the cross and the clock pendulum. Various materials were tried, among others a delicate human hair, the very finest that could be obtained, but this was too coarse and stiff. Its want of pliancy and elasticity gave to the minute "wire cross" an irregular motion, and caused it to rebound from the globule of mercury into which it should have plunged. "After many fruitless attempts," says Prof. Mitchell, "an appeal was made to an artisan of wonderful dexterity—the assistance of the spider was invoked; his web, perfectly elastic and perfectly pliable, was furnished, and this material connection between the wire cross and the clock pendulum proved to be exactly the thing required. In proof of this remark I need only state the fact that one single spider's web has fulfilled the delicate duty of moving the wire cross, lifting it, and again permitting it to dip into the mercury every second of time