Page:Popular Science Monthly Volume 9.djvu/298

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276
THE POPULAR SCIENCE MONTHLY.

Fig. 11.

tain number of times, until I have put sufficient torsion on the fibre D to lift up the beam. Now, according to the law of torsion, the force with which a perfectly elastic body like glass tends to untwist itself is directly proportional to the number of degrees through which it has been twisted; therefore, knowing how many degrees of torsion I