468 N. L. BOWEN 
2. The order of beginning of crystallization is shown in the 
effusive types, which may be regarded as the “‘quenched”’ equiva- 
lents of plutonic types. : 
3. Taking the evidence of both the plutonic and effusive types, 
diagrams are given indicating the course of crystallization in 
granite, syenite, quartz diorite, diorite, and gabbro. 
4. Certain consequences upon theories of differentiation are 
pointed out. 
The writer is indebted to Professor J. P. Iddings for helpful 
suggestions. 
