Chemistry. — “Some Remarks concerning the Ronreunograms 
obtained by means of Mica-Piles composed by crossed 
Lamellae”’. By Prof. F. M. Jararr. 
(Communicated at the meeting of October 30, 1920). 
In a paper recently published *) on the RÖNTGEN-images obtained 
by means of a system of muica-lamellae crossing at definite angles gp, 
it was said in a Note on page 821, that the image obtained was 
evidently mot a mere superposition of the images which were 
obtained by means of each of the composing lamellae separately, 
but that the RÖNTGEN-rays, after passing the first lamella, were appa- 
rently influenced during their passage through the next one in such 
a way, that the final result differed noticeably from the combination 
of the single images turned with respect to each other through the 
angle p. This conclusion was founded in the first place on a com- 
parison of the stereographic projections of the composed photographie 
images with the image obtained by the nm times repeated superposi- 
tion of the stereographic projection of the diffraction-image 
produced by a single lamella; and, secondly, on the fact that in 
the final photograph a considerable number of the outer spots were 
absent, which in the image of the single lamella appeared with 
appreciable intensity. At the same time a systematical investigation 
of this phenomenon was planned, because it was in contradiction 
with the usual interpretation of the diffraction-phenomenon now 
generally adopted. 
At my request my colleague Haca was kind enough to make 
the necessary experiments in the Physical Laboratory of this Uni- 
versity; for his kindness and help I wish here to express my thanks 
once more. The result is, as will become clear in the following 
pages, that the conclusion mentioned in the Note on p. 821, cannot 
be considered as justified in its generality; and after these investi- 
gations we are compelled to acknowledge, that the images formerly 
obtained must really be considered to be, at least in their principal 
features, superpositions of the images of a single lamella, turned 
with respect to each other through angles p,‚ although certain devia- 
tions are certainly present, the causes of which will be explained 
further-on. 
1) F. M. JAEGER, Proceed. R. Acad. of Sciences Amsterdam, 22, 815, (1920). 
