Page:The fairy tales of science.djvu/378

 between the two is precisely that which exists between the opposite punishments of vertically crushing a man to death under a heavy weight, and of horizontally tearing him to pieces by horses.

This theory, confused as it may appear in words, can at once be simply and most beautifully illustrated by any small straight stick freshly cut from a living shrub.

In its natural form the bark or rind around the stick is equally smooth throughout; but if the little bough, held firmly in each hand, be bent downwards so as to form a bow, or in other words to represent a beam under heavy pressure, two opposite results will instantly appear. The rind in the centre of the upper part of this stick will be crumpled up, while that on the opposite side will be severely distended; thus denoting, or rather demonstrating, what we have stated&mdash;namely, that beneath the rind the wood of the upper part of the stick is severely compressed, while that underneath is as violently stretched: indeed, if we continue to bend the bow until it breaks, the splinters of the upper fracture will be seen to interlace or cross each other, while those beneath will be divorced by a chasm.

But it is evident, on reflection, that these opposite results of compression and extension must, as they approach each other, respectively diminish in degree, until in the middle of the beam, termed by mathematicians its neutral axis, the two antagonist forces, like the celebrated Kilkenny cats, destroy