( 252 ) 
es Width | Theor. width Measured width. 
Aine . of the i of image _ 
mark. | second slit. ee diffraction A | B. C. Moa 
1 27 pm 69 p et) | 1.0 | 1.0 DD u 
2 22,5 GO 0583140485 1400 50 
3 19,5 54 0.75 170,75 0/8 A) 
4 18 yl 0.6 OW Oey 40 
5 17 49 0:55 WIT 7 3D 
6 16 47 0.45 | 0.65 | 0.65 30 
7 14 43 0.4-| 0.6 | 0.65 30 
| 
8 | 12 | 39 0351055 | 0.6 95 
Ds) 0,5 4 | 0.3. | 0.4 | 0.6 25 
10 S 31 12023 Oss O25 20 
11 6 27 |} 0.4 | 0.4 | 0.55 
411/, 10.6 | 0.45 | 0.6 
12 4 | 93 4 0.45 | 0.7 
121/, lat Allo Sr dele 
13 3.5 22 | +1, 
When considering these figures we must keep in view that the 
image on account of the width of the first slit is not sharply 
outlined but is hazy; this causes the measurement to remain uncertain 
and so somewhat deviating figures are found by different observers or 
by the same observer at various times; all measurements, however 
taken, proved, as can be noticed from the figures mentioned in the 
table, that for the wzde part of the slit the figures of the third column 
are larger than the corresponding ones of the last column. The 
figures of this third column indicate the theoretic width of the image 
for the case that the plates have been affected to the outer edge of 
the rays to which they were exposed and that no diffraction, vibra- 
tion, displacement or photographie irradiation has played a part; the 
latter three causes might bring about a broadening, yet this would 
necessarily have been greatest on the places of greatest influence thus 
at the wide part of the slit. Now that no broadening whatever is found 
there, the brush-shaped broadenings, whose width is 2 or 8 times 
greater than the theoretic, found on all the three plates at the narrow 
part of the slit, can certainly not be attributed to those three causes. 
