419 
dually become larger; 2. constantly particles disappear; 3. a 
certain number of them is charged and by a constant eleetric field 
these are conducted to one of the condensator plates; +. the eloud 
of ammonium chloride especially undergoes still a change which 
becomes obvious by the change of sign of the double refraction 
from positive to negative; perhaps this is connected with a change 
in form or the change in dimensions, mentioned sub 1, of the 
small erystals. In my dissertation L will show in what way I tried 
to overcome these disturbing influences. 
4. Results of the measurements. 1 first measured the double re- 
fraction of the @-modification and that in an alternating field. The 
condensator vessel used’ for this and also for all the following ex- 
periments of this paragraph had plates on the inside; it had the 
following dimensions: length 44,5, height 10 em and inner width 
9,5 mm, while to the middle of the vertical sides strokes of tinfoil 
of 40> 4 em. were applied. The observations were made photo- 
graphically. 
With one plate 4 observations were made: 
one without field and then successively for the tensions V,, V, 
and V,. In the ordinary way this plate was developed and treated 
further. Afterwards the distances were measured on it. Then the 
@ GA. 3G a 8 
values —, —, — and — are known for the four observations and 
Dug D 0 b 
. : aa : : 5 
therefore also the ratios -—— ete. which are proportional with 7,— 1, 
) 
of the cloud for fields of V, etc. 
In order that the cloud may not be changed during the four 
a,—a Od é 
measurements, rs must be equal to In some cases this 
) 
difference was rather small, as is shown by this table. 
ara aa | 
| b b 
0.106 0.104 
0.050 _\_ 0.056 
kont. |< Soe al 
0.071 | 0.085 
