112 HISTORICAL GEOLOGY 
In the alcoves of the hall is the general collection of meteorites, 
which is one of the largest and most representative in this 
country, containing as it does specimens from about five 
hundred of the seven hundred falls and finds that are known throtea 
the world. Some of the principal features of our collection are: 
Two thousand or more individual masses from the “stone shower” 
that fell near Holbrook, Arizona, in 1912. These have been arranged 
in a case by themselves. 
The whole mass of Ysleta, a newly discovered “1914” iron meteorite, 
weighing 310 pounds from near the ancient village of Ysleta, New 
Mexico. 
A series of polished and large etched slices OF iron meteorites, includ- 
ing an entire section of the new Mt. Edith, Australia, mass, showing the 
Widmanstatten lines in great perfection, and polished slabs from several 
Meteorites 
large stone meteorites. These are in a case by themselves which like- 
wise contain several comparatively large entire single masses of some 
famous falls. 
In the desk cases down the center of the hall are the types and 
figured specimens used by James Hall, R. P. Whitfield 
and others in the original description and none of 
species, or in their further elucidation. 
The specimens in the cases on the left or west side of the hall are being 
arranged to illustrate stratigraphic geology, beginning at 
Types 
Stratigraphic the south (entrance) with the Archean rocks, which are 
or Historical 
~ Geology the lowest and oldest of all and contain no fossils, advanc- 
ing regularly through the Cambrian Ordovician, Silurian, 
Devonian, Carboniferous, Jurassic, Triassic, Cretaceous and Tertiary. 
Most of the specimens on exhibition are from American localities and 
the species are arranged according to their position in the scale of life, 
the lower, or simpler forms being placed first. The specimens shown 
are those particularly characteristic of the various horizons, the object 
being to give an idea of the general character of the life of different 
periods of the world’s history. The ends of some of the cases contain 
large or striking fossils. 
The specimens on the east, or right, side are being arranged to 
illustrate biologic geology, the classification and relation- 
ship of the plants and animals of past geologic times. 
The series starts with the plants and is followed by the 
various sub-divisions of the animal kingdom, again beginning with the 
lower, or simpler forms and continuing to the highest. 
In the first alcove on the right is the stump and part of the roots of 
Biologic 
Geology 
a large tree from an anthracite coal mine under Scranton, Pa. Millions 

