Jagadish Chandra Bose

“ There was no action on the Galvanometer, when the principal plane coincided with the planes of polarisation of either the Polariser or Analyser.
With ordinary light a piece of Tourmaline of sufficient thickness absorbs the ordinary, but transmits the extraordinary ray. With the piece of Tourmaline used in the last experiment I found both the rays transmitted, but, it seemed to me, with unequal intensities. In other words, one ray suffers greater absorbtion than the other. It seems probable that with greater thickness of crystal one ray would be completely absorbed. ”

“ By means of an Iris diaphragm, the amount of radiation may be varied.
Polariser.—The success of the experiment depends greatly on the care with which the Polariser and Analyser are constructed. Fine copper wire ·2 m. m. in diameter is carefully wound in parallel lines, round two thin sheets of mica. There are about 25 lines for every centimetre. The mica pieces are then immersed in melted paraffin, and the wires thus fixed in situ. By cutting round, two circular pieces, containing the gratings are obtained. The mica pieces are too thin to produce any disturbing effect. ”

“ Theoretically all crystals, with the exception of those belonging to the Regular system, ought to polarise light. But this could not be verified in the case of crystals opaque to light. There is no such difficulty with electric rays, for all crystals are transparent to them. ”