428 
(PrzipraM') and researches in the Amsterdam laboratory). This how- 
ever does not yet explain the double refraction. 
A comparison with the behaviour of the “liqueurs mixtes” in an 
electric, or of the iron of Bravais in a magnetic field is of no value, 
as in those cases the particles themselves are double refracting or 
at least are supposed to be so. For ammonium-chloride this is 
excluded. An explanation may be sought sg: in the direction 
of O. Wrenzr’s “double refraction of beads”. *) 
II. The influence of the electric field on the intensity 
of the transmitted and the dispersed light. 
8. Introduction and method of observation. Some of these pheno- 
mena have already formerly been observed (see 1). In this in- 
vestigation three directions occur: the direction of the incident 
light (L), that of the electric field (V) and that, in which the obser- 
vations are made (W). With respect to each other these directions 
can have different positions. By fixing these by means of the system of 
coordinates PQR (see fig. 8) we obtain the cases of the next table. 
I Sar eae IS 
i BIB 72 
rit ume a Fabs "pa 0? = 
Cl RIE 
PRM RR 
Fig. 8. 
Moreover we may still distinguish the cases in which the incident 
light is unpolarized or polarized in one of the “principal directions”. 
Also the state of polarization of the transmitted or of the dispersed 
light may be investigated. 
The observations were made microscopically or with the naked 
eye. For the first method small condensator vessels were constructed 
with condensator plates of 15 > 15 mm at a distance of + 7 mm; 
for the other a large condensator was used, the plates of which 
i) Spree Phys Zs. 11, 630, 1910. 
2) O. Wiener, Leipz. Ber. 91, 113, 1909, 63, 256, 1910. 
