( 466 ) 
des Rathausturmes in Rothenburg an einer Stelle die Bildung der 
grauen Modifikation des Zinns auftritt, ohne dass unterdessen eine 
so tiefe Temperatur wie im Jahre 1893 geherrscht hätte, kann man 
wohl der Annahme huldigen dass durch Verwehen kleiner Teilchen 
des grauen Zinnes vom benachbarten Postturm auf die Bedachung 
des Rathausturmes, die Erscheinung vor sich ging.” 
Evidently there has taken place “infection’’. 
4. I have also investigated the influence of vibrations on the 
change of white tin into the grey modification. I begin to state that 
my experiments in that direction gave me a negative result. The 
few communications which I wish to make as regards the method 
of working are intended to induce others who may be able to work 
under more favourable conditions than myself, to repeat the expe- 
riments. 
ERDMANN *) and Hyeur ®) have noticed the “tin-plague” in organ- 
pipes. ERDMANN explains this by the vibrations to which they are 
subjected. Although we know now that vibrations alone cannot 
cause the phenomenon (above 20° this is surely impossible) it yet 
seemed to me worth while to try whether mechanical influences are 
likely to accelerate the inversion. Then it is known that a concussion 
or a blow can abrogate a meta-stable equilibrium. One has only 
to think of the crystallisation of supersaturated solutions and super- 
fused substances *); also the spontaneous evolution of gas from 
supersaturated gaseous solutions under those circumstances *), 
The researches of ABEL, NOBEL, CHAMPION, PELLET, BERTHELOT, 
THOMSEN, SPRINGMÜHL and others in the field of explosives have 
diselosed facts of this kind. 
Wave motions and other periodical vibrations may give rise to 
explosions even when their intensity is comparatively small. Nitrogen 
iodide does not explode on a plate or string of low tune, but a 
high tune will cause an explosion to take place. 
On the subject of explosions caused by the explosion of other 
substances, LOTHAR Mryer says: ,Wahrscheinlich hängen diese 
Unterschiede von dem Rythmus der durch die Explosionen erzeugten 
1) Journal für pract. Chemie. 52, 428 (1851). 
2) Ofversigt af Finska Vetensk. Soc. forhandlin. 32. 
8} Compare O. LEHMANN, Molecularphysik. I (1888) 189. According to OstwaLp 
salol is not solidified by violent motion; also compare Lornar Meyer, Dynamik 
der Atome (1883) 397. 
*) LEHMANN, Molecularphysik 2 (1888) 117; (Zeitschrift für phys. Chemie, 22 
(1897) 289; BrerrurLor, Les matières explosives 1 (1883) 130. 
