SUMMARY. 217 



sequent separation of corundum on their crystallization. The 

 protoxides of glucinum and zinc, present in small quantities in the 

 magma, have united with a portion of the excess of alumina, and formed 

 the accessory constituents chrysoberyl and automolite respectively. 

 According to Morozewicz's law the elaeolite-syenite would require a 

 larger quantity of alumina to produce saturation than is the case with 

 an albite-orthoclase rock. Consequently, with very little difference in 

 the percentage of alumina, the latter contains much corundum, whilst 

 the former is devoid of the mineral. 



{ 49 ) 



