416 IT. S. WASHINGTON — IGNEOUS COMPLEX OF MAGNET COVE 



The arrangement of the abyssal rocks is abnormal, and differs radically 

 from most other cases of differentiated masses, in that there is progress- 

 ive increase in acidity toward the periphery, the analogous case at 

 Umptek, in Kola, heing especially mentioned. An explanation of this, 

 based on a process of fractional crystallization or freezing of the magma, 

 which is regarded as a solution, the solvent crystallizing first, is given, 

 and the hypothesis is. applied to other cases. It is suggested that all 

 laccoliths and similar masses of magma may be referred to at least four 

 different types, dependent on the chemical composition of the magma as 

 a whole, the differences between which would be satisfactorily accounted 

 for by the hypothesis. 



