GEOLOGIC VERSES, LITHOLOGIC 243 
and magnitude. Some are like pamphlets, mainly devoted to 
a single subject ; others are monographic in character, either con- 
densed or expanded. A uniform sandstone bed, free from fossils, 
is a comparatively simple record; a section like the Norwegian 
“Silurischen Etagen 2 and 3,’ described by Brégger, is a mono- 
graph of many parts and chapters. The thickness of the book 
is no indication of its scope. 
The investigation of the geology of any given area may be 
described, continuing this similitude, somewhat as follows: The 
various rock formations spread out over the area must be viewed 
as historical documents. Each one contains a record of its 
time, local or provincial, limited or comprehensive in scope and 
has, also, chapters relating to earlier epochs. Each has usually 
various parts, and it may be expressive to say that they are 
written in different languages. The longest chapters may not 
contain the most important parts of the record. Indeed, if the 
observer’s eyes are not properly trained, he may not realize the 
presence of the most valuable chapters. Clearly the geologist 
cannot recognize the essential characters of these documents if 
he fails either to note the important chapters, or, noting them, is 
unable to decipher their meaning. For the latter case, however, 
he may rely on the interpretation of others, provided he gives 
them opportunity. 
The difficulties of these historical studies are greatly increased 
by the imperfections, or the gaps, in the record. Some records 
are not in the rocks themselves, but in their relations, as seen. 
Some volumes are now dismembered, and parts may have been 
lost. Juxtaposition of leaves in the present relations does not 
necessarily imply that they belong to a single volume. Chap- 
ters on the same phase of history, belonging to various volumes, 
may be indistinguishable and lie so related that the student who 
is a specialist in this phase will quite surely group them incor- 
rectly in a single volume if he ignores, or is unable to see, the other 
chapters, by which their proper relations are indicated. It is the 
geologist’s duty to group the various chapters correctly in parts 
and volumes, with an appreciation of their broad significance. 
