Z ELEMENTARY GEOLOGY 
and chapters which, when studied with care, unfold 
a story of changes and progress throughout ages, — 
changes which are still in operation. 
We may well borrow an illustration from human 
history. At present we are all contributing our mite 
toward a record of human progress; and all our ances- 
tors have been doing the same throughout all the time 
that men have lived upon the earth. The events of — 
the day we can see and understand; those of a cen- 
tury since are known with only partial completeness, 
and to truly appreciate them the historian must search 
and study with care; concerning the occurrences of a 
thousand years ago our information is very fragmen- 
tary; and no one knows the actual history of the early 
members of the human family. 
Just so in geology: the changes of to-day can be 
seen, studied, and understood; but the events of the 
past become less and less clear as time lengthens, while 
concerning the earliest chapters of the history we can 
only conjecture. The researches of a multitude of 
men have served to give us the main outlines of this 
earth history; and it is this story that we shall study 
in a brief way. Many pages will be found missing, 
just as would be the case if we were studying the 
records of the ancient Persians; and it will be found 
that there are many events which are still puzzles, and 
about which the best we can do is to speculate. 
