115 



with Cii-Ks, rays (9 mA, ± 25 KV). Tliou£;li this film is thoroughij 

 blackened, only two rings have been obtained. 



It may be suggested, that tlie rings obtained in tliese experiments 

 are ail due to atoms tliat temporarily are arranged in a crystal 

 lattice. The values for the diameters of these rings found in this 

 Comm. exclude a cubical arrangement '). The data are not sufficient 

 to know, whether those temporary arrangements might belong to a 

 crystal structure from an other class of symmetry'). Meanwhile the 

 fact that freezing takes place suddenly at a definite temperature and 

 the possibility of undercooling do not seem to point in the direction 

 of such temporary crystal arrangements. 



Lead b}' these considerations we have made siill a plate of water 

 at ± 0,5° C. The obtained interference figure perfectly agreed with 

 that found at room temperature. At the outward side of the nearly 

 uniform blackening only the intensity proved to be somewhat greater. 

 In this way a second ring develops itself there, an indication of the 

 presence of more double molecules at those low temperatures. No 

 indication was found of the presence of more or greater cry.stal 

 groups. 



') Comp. Comm. N". 10 p. 122, footnote ]. 



5) Nitrogen and argon crystallise cubically : W. Wahl. Proc. Roy. Soc. A 87, 

 p. 371, 1912; oxygen below the melting point first hesagonally: W. Wahl, 

 Proc. Roy. Soc. A 88, p. 61, 1913. 



