Letters on natural magic, addressed to Sir Walter Scott, bart (1868)
Brewster, David, Sir, 1781-1868, Smith, James alexander · London, W. Tegg · leaf 278
255 ACOUSTIC FIGURES. parallel lines, perpendicular to a fourth passing through F and N. But if the point N, where it is pinched, is a little farther from the edge than in No. 3, the parallel lines will change into curves as in No. 4. If the plate of glass is circular and pinched at its centre, and… … the same plate, similarly pinched, the bow is drawn over a part 30° from the pinched point of the circumference, the sand will form six radii as in No. 2. When the centre of the plate is left free, a different set of figures is produced, as shown in No. 3 and No. 4. When the' plate is pinched near…
Scientific recreations
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