PREFACKH 
THERE are already a number of good elementary text- 
books on Geology, and at first it may seem that there is no 
special excuse for the appearance of another elementary 
work. However, it has seemed to me, for some time, that 
there is need of a Geology in which more stress is placed 
upon the dynamic aspect of the subject than is commonly 
given. 
It is partly in the hope that this apparent need may be 
supplied, that this book is prepared. Some may question 
the wisdom of the very notable curtailment of the strati- 
graphic side of the subject, but I believe that it agrees with 
the best educational needs. In this part of geology there is 
too much abstract fact for the average high school student 
to be able to profit from the great truths which these facts 
teach. It is my belief that it is better to state the truths 
without the introduction of these bodies of fact; for, at 
best, in an elementary book only part of the facts can be 
presented. In other words, I believe that the study of 
stratigraphic geology belongs to higher grades than the 
secondary school. At the same time the main truths of the 
subject may properly be presented to the pupils of these 
schools. 
Vii 
