1190 
Assuming, that the maxima arise under the influence of the strong 
yellow light, the width of the slit a is found to be 
a i. 0.539 ED 
ae sin@ sin1°36' Sara 
The side of the base-face thus becomes 0.279 mm. which appears 
to be quite a possible size *). 
Using this value of « the colour-effect can now be derived in 
: . asin |. 
the following manner. The expression Se first calculated 
ascending by 15’ for the same eight colours ‘as used before. 
2 | a sin @ 
Scuwerp °) has computed the intensity as a function of aw from 
asin 0 asin @ s ; : 
Far oar O up to — are 6. By means of a graphical representation 
of these results the intensities for all the above values of the 
expression can be arrived at and the results are then reduced 
to the relative intensities in sunlight. They are then drawn 
graphically for the eight colours taking as abscissae the distance 
from the sun, at which the fringes are formed, the central maximum 
being taken at the minimum deviation. The curves are further used 
as explained before with a view to the dimension of the sun. 
The results are contained in the foregoing table. (See p. 1189). 
The figures in the horizontal rows give the relative intensities for 
the directions contained in the first column. 
These data are then reduced to colour-equations and finally the 
colour-numbers in the colour-triangles as well as the percentage 
of white are computed. Fig. 4 gives the change of the intensity. 
000 
500 
it 
en 
Ee 
len 
300 
vo 
30 
! \ eye ke 
100 {a ! : 
| we a) oe, 
| NR. \ biog os 
23 22 Py) 20 7) 18 7 
Fig. 4. 
1) PERNTER |. c. pag. 287. 2) PERNTER |. c. pag. 453. 
