CHAPTER V. 
GEOLOGICAL SEQUENCE OF ROCKS. 
THE ROCKS NOT IN CONFUSED MASSES — THEY OCCUR IN 
A DEFINITE ORDER — OLDEST ROCKS OF THE MOUNTAINS 
THE TRUE SEQUENCE OF TIIE STRATIFIED ROCKS 
Up to the present we have been considering of 
what materials rocks are made, as well as, how these 
materials were brought together. We now touch on 
the question when and in what order they were formed. 
The stratified rocks are not a confused mass; on the 
contrary, they occur in a definite series, and it is proved 
satisfactorily that this order does not vary, although one 
or more members of the complete series may be wanting. 
Imagine a dozen copies of the same historical 
volume scattered about a room. Each volume, let us 
suppose, is imperfect. Chapters are missing here and 
there ; they have been torn out, or perhaps were never 
bound up with the volume. Although a chapter 
is absent now and again, the order of the chapters 
does not- vary. Chapter X. always comes after Chapter 
IX., or, if the ninth chapter is missing, after Chapter 
VIII. In the same way Chapter XX. always follows 
Chapter XV., even though more than one chapter may 
be wanting between. By a diligent comparison, how- 
ever, of the different volumes, a correct and continuous 
