1 32 Proceedings of tJie Royal Society of Victoria. 



than ill iron in which it is very high. The metals in which 1 

 observed the highest effects are not necessarily those in which 

 the effect is really highest, for I examined some for weeks and 

 others only for a few minutes. Most of the time was spent over 

 iron, lead, and gold (ninety-two per cent.) The purest metal I 

 used was silver, one of the specimens being absolutely pure, and 

 with this the effect was very small. The effect however cannot 

 be altogether due to impurity, for with alloys the effect was not 

 more marked than with moderately pure metals. 



