1285 



II. This accidental predisposition to inn into one another, which 

 according to the laws of pi\)bal>ilitj may be expected along some 

 lines (and which according to the ordinary laws of optics is only a 

 conseqnence of the irregnlar distribntion of the refracting particles) 

 will it snffice to explain the existence of fibres of the observed length ? 

 Evidently the qnestions I and II come essentially to the same. 



Only when these questions had to be answered in the negative 

 we should to have to conclude, that classic optics weie not sufficient 

 to explain the observations. We should then be compelled to assume 

 that already with homogeneous light radial fibres would be found. 

 And as was remarked above if is very difficult to decide this in a 

 direct way. The experiments made with sodium light however do 

 not point in that direction. Another possibility would be that 

 except the above mentioned accidental predisposition there existed 

 still another along some radii. Both this and the former possi- 

 bility would compel us to alter the fundaments of the diffraction 

 theory. 



As to the running into one another of the fibres formed by the 

 spectral shift, this will evidently occur the sooner the longer the 

 fibres are. Now the fibres formed by the spectral shift have a length 

 proportional to the distance to the centre 0, so that the running 

 into one another will occur more at a certain distance from the 

 centre than in its immediate neighbourhood. With this the fact is 

 in agreement that, as was mentioned in ^ 5, the length of the 

 observed fibres increases towards the periphery more than would 

 correspond to the distance from the centre. 



8. Finally some experiments will be described, which (together 

 with the experiments with the sodium light) support my conception 

 of the phenomenon. 



Investigating the diff'raction phenomenon of a screen with about 

 fifty apertures we can prove in a very direct way that in fact 

 the diff"raction figure is built np of interference lines. To do this experi- 

 mentally the ocular of the telescope had been fixed on a small car, 

 which could be moved to and fro over a pair of rails. It is evident, 

 that by a displacement of the car the structure in the diffraction 

 image formed in the focal plane of the objective is effaced in a 

 direction perpendicular to that of the motion. Only when an inter- 

 ference fringe has the diiection of the motion it remains unchanged. 



In fact, when in the indicated way the ocular is quickly moved 

 to and fro, we firstly see how the fibrous structure of the diff'rac- 

 tion image is changed into a homogeneous white spot on which 



