Paleontology 397 



activities may have their influence as shown by the fine beds of coal 

 succeeding layers of sand, or by a layer of large fossils imbedded in 

 limestone. 



As there is a tremendous pressure of the superincumbent layers 

 upon the underlying strata, the lower layers as well as their fossil con- 

 tents are often crushed and injured. Extreme care must, therefore, be 

 taken to interpret one's findings. One can readily grasp what such 

 pressure would accomplish in the delicate layers of shale (called paper- 

 shales), which range from sheets as thin as paper to layers of such 

 sheets fifty feet or more in thickness. 



A study of the fossil remains of plants and animals should show us 

 in what order these organisms lived and followed each other in times 

 long past, and it is usually conceded that they do ; but, it is not an 

 uncommon thing to find an earlier fossil layer lying above a later one. 

 Geologists explain this by saying that changes have again taken place 

 which reversed these lower beds, or thrust earlier strata between other 

 layers. All this complicated arrangement lends itself to deceptive inter- 

 pretation. For example, those who oppose the usually accepted geolog- 

 ical evidence of "periods of time" and "successive ages" say that the 

 arrangement of the various strata is so deceptive, that it can only be 

 explained by a world upheaval of some kind, and that, therefore, no 

 evidence of successive ages is worth anything. 1 



An interesting example of the order in which certain strata have 

 been formed, is found in instances where trees and their stumps are 

 found lying in a more or less semiupright position. Often the stump 

 part and roots still lie in their position of growth, or at least they lie 

 in a deeper stratum than the upper and less heavy portion. Such trees 

 were either pushed over by a stream of water, or carried along by the 

 stream. The heavier end became caught or weighted, and sank, while 

 the upper end remained in a slant position in the direction of the current. 

 It is, of course, also possible that the trees were entirely submerged 

 while still growing. In the latter case, however, the rate of sand deposit 

 must have been sufficiently rapid to lay down an accumulation of at least 

 forty feet (enough to cover the erect tree) before the wood decayed. 



Former regions have been identified by the occurrence of great 

 quantities of driftwood found in the strata, as having been quite close 

 to land ; while differences in climate are evidenced by the finding of- 

 tropic plant and animal remains in cold regions, and arctic plants and 

 animals in tropic regions. 



Migrations of plants and animals from one region to another are 

 demonstrated by the finding of fossil remains in different types of strata 

 in different ages. 



1 G. McC. Price, "The Fundamentals of Geology." 



