6 ELEMENTARY GEOLOGY 
While in a measure one may do this by reading and 
thought, it is best done by an actual study of the earth 
itself. Something may be learned from the printed 
page, but geology is most effectively studied out of 
doors. In chemistry or physics we can read the facts 
from a text-book ; but how much more impressive and 
important is actual experiment! So in geology: it is 
the history of the earth as revealed by the rocks, from 
which every one may decipher a page or two for him- 
self. It is within the power of every teacher to have 
this done; and on his way to and from school, every 
student can find a lesson. 
The rock by the roadside is crumbling and forming 
soil; yet our fathers have passed this spot for a quarter 
or half of a century, and it has remained almost un- 
changed. This slow action of rock-crumbling has in 
some places produced a layer of soil many feet in depth, 
and the time consumed in its production must have 
been very great. When the snow melts, or the rain 
falls, the rivulet is swollen to a torrent, and is laden 
with mud. It is carrymg many fragments of soil and 
rock, and each day it is doing a tiny bit toward the 
enlargement of the valley which it occupies, and which 
it has formed; but in the lifetime of the oldest resi- 
dent, no notable change has occurred. These are some 
of the lessons to be learned on every hand. 
From what is written just above, one can see a second 
