The Emerald Catherine the Great by Hilaire Belloc

Many of our most important modern inventions have been forestalled by the Chinese, for whom we should have the greater regard in that they are not Christians. Gunpowder, False Money, the art of Printing, Diplomacy, Propaganda, Prison Fortunes, Taximeters and the Strike -- all these are of the extreme Orient. But what have I to do with all these? It is of the Mariner's Compass that I sing -- which also was first spotted by the Chink.

Now of the various forms of Mariner's Compass there is one with which some few of my readers may be acquainted. It is used in certain scientific experiments which have nothing to do with pointing to the North, but with the measurement of delicate electrical hints. The needle swings on a jewelled pivot, very nicely balanced, encased in a small round box about an inch across, covered in with glass so that no dust can affect the very sensitive affair; and at the side there is a little stud on a spring which you press with your finger when you want to fix and register the pointing of the needle. So long as you press the stud the needle stands firm. When you release the stud the needle trembles again.