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Abstract In my previous papers I have given accounts of the doubly refraction and polarisation of electric waves produced by various crystals and other substances, and also by strained dielectrics. A account was there given of the polarisation apparatus with which the effects were studied. In the present investigation effects has to be studied which were exceedingly feeble. The apparatus has therefore, to be made of extreme sensitiveness; but the secondary disturbances became at the same time more prominent, and the great difficulty experienced was in getting rid of these disturbances.
Jagadis Chunder Bose (Sat,) studied this question.