Six lectures on light : delivered in America in 1872-1878 (1886)
Tyndall, John, 1820-1893 · New York : D. Appleton · leaf 177
The magnet produces an effectequivalent to this rotation. The puce-coloured circleis now before you on the screen. (See fig. 46, where 146 ON LIGHT. LBCT. N is the nozzle of the lamp, H the first Nicol, Q thebiquartz plate, L a lens, M the electro-magnet, withthe heavy glass across its poles, and P… … The action, moreover, depends upon the polarityof the magnet, or, in other words, on the direction ofthe current which surrounds the magnet. Eeversingthe current, the red and green reappear, but theyhave changed places. The red was formerly to theright, and the green to the left; the green is now…
Light
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