1895.] 
J. C. Bose — Polarisation of Electric Rays. 
EXPLANATION OF PLATES. 
291 
PLATE III. 
Fig. 1 . Lambrachgeus remifer, cf . 
„ 2. Physachaeus ctenurus, £ ; 2a. abdomen of 7 x 4; 26. abdomen of 
<J x 4. 
„ 3. Physachaeus tonsor, $ 
■» 4. 4 a. Grypachaeus hyalinus, 2 . 
PLATE IV. 
Fig. 1. la. Inachoides dolichorhynchus, cf. 
,, 2. 2a. Apocremnus indicus, <f. 
„ 3. Naxia investigators s, cf. 
,, 4. Macrocceloma nummifer, cf. 
„ 5. Maia gibba, cf. 
PLATE V. 
J 
( 
Fig. 
1 . 
5 J 
7) 
2 . 
3. 
4. 
Achaeus cadelli, cf. 
2a. Chorilibinia andamanica. 
Callodes malabaricus, 9 • 
4a. Paratymolus hastatus, ? . 
On Polarisation of Electric Rays by Double Refracting Crystals.—By Prof. 
J. C. Bose, b.a., (Cantab.) B. Sc. (Lonb.) 
r s f r . t 
[Read 1st May.] 
Plate YL 
A ray of ordinary light incident on a crystal of Iceland spar is 
generally bifurcated after transmission, and the two emergent rays 
are found polarised in planes at right angles to each other. The object 
of the present inquiry is to find natural substances which would polarise 
the transmitted electrical ray. It was thought that the analogy be¬ 
tween electric radiation and light would be rendered more complete, 
if the classes of substance which polarise light were also found to 
polarise the electric ray. The identity of the two phenomena may 
be regarded as established, if the same specimen is found to polarise 
both the luminous and electric rays. 
As the wave length of an electrical ray is very large compared with 
that of visible light, one would think very large crystals, much larger 
than what occur in nature, would be required to show polarisation 
of electric rays. By working with electric radiations having very 
J. n, 37 
