999 



Various aequivalents of tlie basalts and aeqiiivalents of the andesitic 

 rocks of the Goentoer in a broader sense were found among the 

 liomoeogeneous inchisions of tlie youngest eruptive products of the 

 Goentoer properly speaking. 



The quartz-containing inclusions of the basalts of Krakatau illustrate 

 the presence of virtual ([uartz in the groundmass of the hypersthene 

 andesites of the first period, and would as well be the only traces of 

 diflerentiation in the inother-magnia before the basaltic eruptions, if 

 not, not only the greater par-t, but all traces of the former basic 

 eruptions had disappeared by a fall-down. 



The occurrence of augitefree plagioclase-hypersthene-amphibole- 

 olivine rocks as liomoeogeneous inclusions in the products of the 

 Goentoer teaches us that such combinations of minerals may at a 

 greater depth crystallize out of the basaltic magma. 



It appears from the calculation of the norm that also the quartz- 

 containing inclusions of Krakatau belong to the rare combinations 

 of minerals because, according to the analyses calculated by Washing- 

 ton no other rock belongs to the sub-class (II. 3, 4, 3). 



Chemistry". — ''On the pyrophovic phenomenon in metals''. By 

 Prof. A. Smtts, a. Kkttnki?, and A. L. W. de Gee (A pre- 

 liminary communication). (Communicated by Prof. J. T). van 



DER Waals). 



.(Gomüiunicated in the meeting oi' February 28, 1914.) 



In a previous communication ^) it was pointed out that the 

 pyrophoric phenomenon would possibly have to be explained by 

 this that the metals obtained in the reduction of certain compounds 

 are comparatively far from the state of internal equilibrium and 

 show an abnormally great |)Ower of reaclioji in consequence of 

 an abnormally large content of the sinipler kind of molecule. 



The exi)lanation for this pheiioiuenon prevalent up to \m\\, which 

 is of more frequent occurrence than is perhaps supposed (we found 

 it with Cu, Bi, Pb, Ni, Fe) attributed the great reactive power to 

 the very finely divided state; so an explanation which is perfectly 

 analogous to that of the so cr.lled '"chemical tlag" for |)hosphorus 



Now the possibility might also be considered that in the liberation 

 of the metal a pyrophoric admixture is formed, or that the hydrogen 



1) Theye Proc. XVI, p. 690. 



