444 



slriiction-figiire, relating (o our [)a|)er on the i^y mmetry oï bo racite ^); 

 tliis figure will reprO'luce tiie t'liaiiges oI)sci'ved by us with this 

 mineral before and after heating, in a clearer way, than the not 

 very satisfactory j)hotographieal reproductions given in that paper. 

 In constructing this stereographical projection, Dr. L. S. Ornstein 

 has given us again his kind assistance, for which we thanlv iiim here 

 also once more. The change of the binary axis into the quaternary 

 one, is proved by this figure again in a very striking manner, and 

 it is easy to see. which reticular planes of the molecular structure 

 have disappeared at higher temperature. 



At the same time we will correct some errors in the former 

 paper, where on p. 797 the words "right" and "left" need to be 

 int-erchanged several times, because the photographs are urdiappily 

 placed in reversed j)Osition, so that on comparison of the text and the 

 tignres, there is a confusion of right side, left side, and of horizontal and 



Boracite at room temperature. 



1) H. Haga and F. M. Jaeger, these Proc. loco cit. 798 (1914). 



