Physics. — "Investigation by means o f X-rai/s o/ the cri/stal-struciure 

 of lohite and c/rey tin. II. Tlie structure of inhite tin." Com- 

 munication N'. 2(1 from the Laboratory of Plijsics and 

 Physical Chemistry of tfie Veterinary College at Utrecht, by 

 A. J. Bui. and N. H. Kolkmkuek. (Communicated on behalf 

 of Prof. W. H. Keksom, Diiector of the l^aboratory, by Prof. 

 H. Kamerlingh Onnes). 



(Communicated in the meeting of September 2S, 1918). 



In Communication N°. J (June 1918) we conjmiinicated, that we 

 had taken Röntgenograms of while and grey (in by the method of 

 Debije and Schehkkr and we gave a description of some particulars 

 about the arrangement of these measurements. Moreover we showed 

 in a drawing for both states of tin mentioned the places of the inter- 

 ference-maxima in a plane, per|)endicular to the axis of the bais, 

 indicating at tlie same time the intensities of the interference-lines. 

 The photo of the grey tin indicated, that this material is crystalline, 

 and on comparing the piiolos for the two states, it was evident, 

 that it possesses a crystal-structure, whicli differs from that of white 

 tin. We have now determined from (hose photos the crystal-structure 

 as well of white as of grey tin, and shall commnnicate in this paper 

 our resiUts for white tin, reserving those for grey tin for commu- 

 nication N". 26 (these Proceedings). 



In table I the intensities of the interference-lines are inserted in 

 the tirst column: vf means very feeble, f feeble, m moderate, s strong 

 and vs very strong. 



In the second column are inserted, expi-essed in tenths of mm, 

 the distances of the intersections of the interferejice-lines with a 

 plane through the axis of the incident Röntgen-beam and perpendi- 

 cular to the axis of the preparation, to the point where that first 

 axis, prolonged, would meet the film, measured on the film when 

 developed on a plane. In the third column (he values of 5m' \/, 

 are ranged, as computed from the above-mentioned distances and 

 the data of the apparatus, wliich were given in Comm. N". 1. 



Now the values, given in the third column must undergo a 



