CHAPTER XXVI. 



PALEONTOLOGY 



Just as we attempt to read and interpret the history of man's prog- 

 ress in the handicrafts, and in the remnants of tools and pottery which 

 are found in various parts of the world, so we attempt to read and in- 

 terpret the changing conditions which have taken place in the earth's 

 crust by the study of geological and paleontological findings. Geology 

 concerns itself with the changes in the earth itself, while paleontology 

 seeks to build up a meaningful account of the changes which may have 

 taken place in living organisms throughout the past, as demonstrated 

 by their fossil remains (Fig. 245). 



There are two general ways in which layers of rock and soil have 

 been laid down. The first has come about by great masses of molten 

 substance forming within the earth which were then thrown out by 

 volcanic action. Such masses harden to form minerals and other heat 

 products. If the minerals then become concentrated, they are called 

 ores. All such products formed by heat are known as igneous forma- 

 tions. 



The second way in which changes have come about is this : Various 

 horizontal soil-layers have been shifted about by climatic changes such 

 as a subsiding of land surfaces and an elevation of the edges of the ocean. 

 This causes the lowered continent to be covered by shallow water, and 

 later, when this condition is again reversed, a layer of sediment is left 

 behind. It is in this sediment that millions of marine-forms of life are 

 stranded. If now, the sediment hardens, and these marine organisms 

 are safely protected from air and superficial decay, their bodies will be 

 preserved as fossil remains. 



Fossil remains are, therefore, observed most frequently in the de- 

 posits on the floors of lakes, in peat-marshes, in the deltas of river- 

 mouths, and under the stalagmites in caverns in lime-stone districts. 



The exceptional conditions necessary to preserve organic forms will 

 rarely be found everywhere, so that we must remember that no matter 

 how many fossil remains may be found, only a very infinitesimal por- 

 tion of the living forms of any given period will become known to us. 

 Then, too, in those which are preserved most, if not all, of the softer 

 parts of the organism are destroyed, only the hard portions remaining. 



The necessity for coordinating the facts found in many and vary- 

 ing ways is of prime importance in the science of Paleontology, for 

 without such coordination there is neither sense nor value in its study. 

 This will be demonstrated quite clearly in what follows. 



Geology and climatology attempt to explain each other, the former 



