408 



very feeble, feeble, moderate, strong, and verj strong. X)u the axis 

 of the drawing the greatest error, that possibly is made at the 

 readings is indicated by the distance of two little lines (to the left). 



From the })hoto of the grey tin it follows in the first place that 

 this material is crystalline, which fact, so far as we conld find, at 

 present was nnkiiown. ') Further there appears to be a difference 

 between the crystal-strnctnre of grey and of white tin. We intend 

 soon to communicate the composition of both the atom-nets. 



In concluding we thank Prof. Keksom very much for the kindness 

 with which he placed all the requisite apparatus for the experiments 

 at our disposition and for his interest and cooperation. 



[Note, added during the ttanslalionl. After lliis communication had been 

 printed in the Dutch edition, we found, tliat vo.n Foullon (Jalirb. d. Kais.-Kön. 

 Geo], Reichsanst. Wien. 34 (1884), p. 867) as well as Fkitsche (Ber. d. d. Chem. 

 Ges. 2 (1869), p. 112 and 540) assert, that grey tin is crystalline. It does not 

 appear in what manner these scientists have verified the crystalline condition. 



