18 PROCEEDINGS OF THE INDIANAPOLIS MEP:TING. 



Thus all four of these early authorities in English geology agree in their definition 

 of the original Carboniferous system, which is that of the series of rocks typically 

 represented in the Pennine range of England, and not fully represented in any other 

 one section of England. 



When we seek to determine the precise definition of the Carboniferous system, we 

 are led directly to the typical section in the Pennine range first clearly defined by 

 Conybeare and afterward adopted as the typical section by the founders of geologic 

 science in England, and afterward by correlation recognized as the standard section 

 of the Carboniferous system throughout the world. 



The section of this typical Pennine Carboniferous system consists of, first, the upper 

 part of the Old Ked sandstone resting upon lower beds of Old Red sandstone, un- 

 conformably about the Cheviot hills, or upon the Cheviot volcanic series, or upon 

 Silurian rocks, as in Northumberland. The second formation, resting conformably 

 upon the first, is the " Mountain or Carboniferous limestone." The third member 

 of the series is the " Millstone grit and shales ; " the fourth, the " Coal Measures," 

 including the familiar coal fields of Lancashire and Cheshire, of Yorkshire, Northum- 

 berland and Derbyshire. These latter are terminated, where contacts are seen, by 

 the New Ked sandstone, in some places apparently conformably but generally un- 

 conformably. 



The system in this Pennine range was evi 'ently terminated both below and above 

 by geologic disturbance of greater or less extent, furnishing natural delimitations, 

 thus peculiarly fitting it for a stand rd of geologic definition. 



An anal3'sis of the standard schemes in geologic classification shows us that a system 

 is a series of rock formations whose stratigraphic order and lithologic composition 

 are thoroughly well expressed in some definable geographic region, and whose fossils 

 indicate a continuous biologic sequence, more or less distinctly broken at its lower 

 and upper limits from contiguous formations. 



Thus a typical system has definite geographic position, geologic delimitation, and 

 biologic definition. 



The Silurian system in Wales and western England, the Devonian system of 

 South and North Devonshire, the Jurassic system of the Jura mountains, are exam- 

 ples, and no less perfect is the Pennine carboniferous system of the Pennine range 

 of North England; to which the unsatisfactory name of Carboniferous has been so 

 long applied. 



While so much is true of the standard or typical expression of a geologic system, 

 it cannot be expected that any system will offer precisely the same features in other 

 regions of the world or on other continents : 



1. Because the composition, the size of particles, and the order and thickness of 

 deposits are all determined by conditions that are geographically dissimilar, a geologic 

 system can have but one typical geographic position. 



2. Because the geologic events, such as elevation of land, breaking of strata re- 

 corded in faults, and volcanic eruptions, do not take place either uniformly or simul- 

 taneously in different parts of the earth, it is certain that intervals or breaks in sedi- 

 mentary formations will not be uniform for separate regions. 



3. Because organisms in the past cannot be regarded as having ceased to carry on 

 the ordinary functions of life and reproduction, all the breaks in the sequence of 

 organisms, all the sharp lines distinguishing the faunas or floras of one formation from 

 those of a preceding or following formation, are local and not universal. 



To apply these reflections to the present case, it will be seen that the settlement as 

 to which is the typical section upon which the Carboniferous system was founded 



