Crystals are everywhere, in living substances, like the Gbres of hair or wool or horn—as well as in nonliving matter. It has lately been hopefully suggested that in some needle-like crystals got out from a vegetable poison a link might be found between the living and the dead.
This secret of a crystal, recently mentioned by Sir William Bragg, President of the Royal Society, is likely to remain a secret still, though the crystal itself has been probed by X-rays, by polarised light, and photography, and its monstrous molecule of 17,000,000 atoms has been measured and weighed. But other examples of crystal gazing, as pursued by Sir William Bragg, his son, Professor W.
L. Bragg, an army of investi all over the world, are of immediate importance to science and industry which rock salt is made. But in the crystal cells a million atoms are spread out over an inch. In a cubic uch are trillions The eye could never see them. To see them with any ultra microscope would be like trying to pick up a grain of sand with a steam dredger. But the X-ray eye is more particular, having a wave-length of light one hundred thousandth of any the human eye can use. Its light rebounds from zn atom in the crystal, or spreads out in smaller waves from it. By reflection from the atoms spaced out in the crystal cells, the X-rays throw what we may call (rather sketchily) a shadow pattern of their arrangenent on a screen, There is no such thing as a surface reflection, because the rays must pass through millions of crystal lay-before their exploratory results X-Ray Eye of this army, equipped ray as a weapon, is to ud how the atoms are arranged in al and how they may be ow themselves, We might turn the crystal through innumerable angles to its pattern. In practice, powdering crystal and sending the exploratory ray through the mass gives the result. d. The X-ray is the only capable of spying out this ultimate Picture of a Cell structure.
Its inquisitiveness has shown why paints t like behave differ ently when applied; why chromium-plated articles differ in brightness or
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