Page:Collected Physical Papers.djvu/37

Rh holding the Tourmaline vertical, the Receiver at once responded.

I next experimented with a piece of Nemalite. The crystal I used was a very small one, only one cm. in thickness, but this comparatively thin piece exhibited unusually strong depolarising action. It is therefore highly probable that a sufficiently thick piece of Nemalite would make an efficient Polariser.

Experiment with Jute Cell

The most efficient polarising substances I have come across are the vegetable fibres. Among these may be mentioned the fibres of Aloes (Agave), Rhea (Boehmeria nivea), Pine Apple (Ananas sativus), Plantain (Musa paradisiaca).

Common jute (Corchorus capsularis) exhibits the property of polarisation in a very marked degree. I cut fibres of this material about 3 cm. in length, and built with it a cell with all the fibres parallel. I subjected this cell to a strong pressure under a press. I thus obtained a compact cell 3×3 cm. in area, and 5 cm. in thickness. This was mounted in a metallic case, with two openings 2×2 cm. on opposite sides, for the passage of the radiation.

The polarising grating was removed, and the Analyser arranged with its vibration plane vertical. The jute cell was now interposed with its fibres horizontal, and the Receiver was found to respond energetically.

The cell was now placed with the fibres vertical, and there was now not the slightest action on the Receiver.

The fibres were now inclined at 45° to the horizon. There was an immediate response in the Receiver