Tyndall, John, 1820-1893 · New York : Appleton · leaf 259
250 SOUND. my hand and cause the image to pass over the screen.Were the flame silent and steady, we should obtain a con-tinuous band of light; but it quivers, and emits at thesame time a deep and powerful note. On twirling the Fig. 117. U … mirror, therefore, we obtain, instead of a continuous band,a luminous chain of images. By fast turning, theseimages are drawn more widely apart; by slow turning,they are caused to close up, the chain of flames passing RHYTHMIC IGNITION AND EXTINCTION. 251 through the most beautiful variations.…
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