HISTORICAL GEOLOGY 119 



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, 

 weighinjj; 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 <>ntire section of the new ^It. Edith, Australia, mass, showing the 

 Widnumstatten lines in great perfection, and jiolishetl slabs from several 

 large stones meteorites. These are in a case by themselves which like- 

 wise contains several comparatively large entire single masses of some 

 famous falls. 



An exhibit of met(>oritic masses, decomposition products, and country 

 rock showing unalteretl mat(>rial and that which was melted and other- 

 wise altered by the impact of the Canyon Diablo meteorite at the spot 

 now known as Meteor Crater, Arizona. This exhibit has been loaned to 

 the iMuseum by Princeton University. 



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 naming of 

 si)ecies, 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 

 btra igrap ic ^j^^ south (entrance) with the Archean rocks, which are 

 GeoloEv ^^^ 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 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- 



ships 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 

 a large tree from an anthracite coal mine under Scranton, 

 Pa. Millions of years ago, in the geological period known 

 as the Carboniferous, this tree grew upon the top of a 



