60 
IOWA ACADEMY OF SCIENCE Vol. XXIY, 1917 
problems will be solved as rapidly by disproving terranal re- 
lationships as by showing that they exist. Rate of advance- 
ment is thus doubly accelerated. Inattention to these circum- 
stances is doubtless the chief reason why progress in Pre-Cam- 
brian geology has been so unnecessarily slow and why so few 
investigators find the field inviting. 
Bes Moines. 
