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18 but the radiation was completely extinguished by rotating the Analyser till the grating crossed the fibres. On continuing the rotation, the Receiver responded most when the wires of the grating and the fibres became parallel. Keeping the jute cell fixed at 45°, it was found that during one complete rotation of the Analyser, there were four positions of extinction (when the wires and fibres crossed), and four positions of maximum transmission (when the wires and the fibres were parallel).

From the above experiments, it is quite clear that a jute cell produces complete polarisation of the transmitted ray, the plane of vibration being perpendicular to the fibres.

Two jute cells were then made, and the gratings discarded. One of these acts as a very efficient Polariser, the other as an Analyser. When the two are crossed, the electric radiation is completely extinguished.

In the polarisation apparatus described above, three different types of Polariser (or Analyser) can be used:—


 * (1) The wire grating Polariser.


 * (2) Polariser made of crystals like Tourmaline or Nemalite.


 * (3) Jute or vegetable-fibre Polariser.

The apparatus may also be used as a Polarimeter, the rotation of the Analyser being easily measured by means of the graduated disc. (The Electrician, Dec. 1895.)