Page:Life in Motion.djvu/98

78 arrangement by which I can attach a glass plate to the side of one of the limbs of the fork, and I have placed exact counterpoises on the other limb. I now blacken the slip of glass

(an ordinary microscopic slide) in the smoky flame of this lamp and attach it to the fork. Set the fork vibrating. I shall now write something on the smoked surface with a needle point, taking care to write at right angles to