CAVES L13 



menting what is shown by the models. The work of treating the ore at 



the smelter in Douglas Dear Bisbee is demonstrated in a neighboring ca e. 



The northwest corner of the hall contains a display of caves and cave 



_ materia] the most important feature of which is the PeprO- 



Caves 



duction of part of a beautiful cave thai was discovered early 



in 1910 in mining operations at the Copper Queen mine. The cave was 



formed by the dissolving action of water traversing joints in limestone, and 



its walls, roof and bottom were afterward coated with calcite (calc spar) 



incrustations, stalactites and stalagmites, some of which are dazzling white 



while others are colored green with copper salts or pink with manganese 



compounds. 



Alongside the Copper Queen cave a reproduction of a chamber in Weyer's 

 Cave, Virginia, is being installed. Weyer's Cave is in a region of much 

 heavier rainfall than Bisbee, which is probably the principal factor in pro- 

 ducing a greater wealth of regular stalactite and stalagmite growth than 

 adorns the Copper Queen cave. 



The cases along both sides and down the middle of the hall contain 

 geological and pakrontological specimens. Palaeontology is the science 

 of the ancient life of the earth; its field is the study of the fossilized shells 

 and other hard parts and the various kinds of imprints left by the animals 

 formerly inhabiting the seas and lands, and preserved in deposits which 

 now form our stratified rocks. As normally the upper layers of a series of 

 strata are more recent than the lower, the fossils reveal the succession of 

 life forms in the earth's crust and thus are of the highest value and interest 

 to the student of historical geology. Since, however, the remains of only 

 a small proportion of the animals living at a given period are permanently 

 preserved in the marine, river, lake and subaerial deposits of that period, 

 the geological record of animal and plant forms is far from complete. Inas- 

 much as invertebrate animals are far less free in their movements than the 

 vertebrate forms, they are accepted as the best determinants of the geologi- 

 cal age of a bed of rock, even when remains of both kinds are found together. 

 Invertebrate life, too, appeared on the globe far earlier than vertebrate, and 

 remains of certain species are abundant in the low r est (oldest) of our stratified 

 rocks. 



The specimens in the cases on the west side of the hall are being arranged 

 to illustrate historical geology, beginning at the south (en- 

 G , trance) w r ith the Archean rocks, which are the lowest and 



oldest of all and contain no fossils, advancing regularly 

 through the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, 

 Jurassic, Triassic, Cretaceous and Tertiary. Most of the specimens on ex- 

 hibition are from American localities, but a synoptic series of European 

 fossils is exhibited in the northw r est quarter of the hall. The desk cases 

 in the middle of the hall contain overflow material from the sides. Under 



