1 88 THE JOURNAL OF GEOLOGY. 



Class II. Transition rocks — including (i) transition lime- 

 stone, (2) transition trap, (3) greywacke, (4) 

 transition flinty slate, (5) transition gyp- 

 sum. 

 Class III. Floetz or secondary rocks — including (i) old red 

 sandstone, (2) 1st floetz limestone, (3) ist 

 floetz gypsum, (4) 2d variegated sandstone, 

 (5) 2d floetz gypsum, (6) 2d floetz limestone, 

 (7) 3d floetz sandstone, (8) rock salt forma- 

 tion, (9) chalk formation, (10) floetz trap 

 formation, (ii) independent coal formation, 

 (12) newest floetz trap formation. 

 Class IV. Alluvial rocks — including (i) peat, (2) sand and 

 gravel, (3) loam, (4) bog iron ore, (5) nagel 

 fluh, (6) calc tuff, (7) calc sinter. 

 Notice in this classification that the "coal formation" is 

 placed near the top of the secondary rocks, the "rock salt for- 

 mation" near its middle, and the "old red sandstone" at its 

 base. Later investigations did not confirm Maclure's opinion of 

 the accuracy of Werner's system as applied to American rocks. 

 Amos Eaton's classification of New York rocks (as exhibited in 

 his "Geological and Agricultural Survey of the district adjoining 

 the Erie Canal in the State of New York, Albany, 1824) is an 

 elaboration of the same system. 



In each of these classifications, except in a few cases of the 

 retention of distinctions based upon the structural analysis, the 

 whole nomenclature and classification is based upon mineralo- 

 gical composition of the rocks. In the succeeding progress of 

 the science a great part of the nomenclature has been replaced 

 by other names composed on a different principle, but many of 

 the divisions here recorded are still retained. This latter fact we 

 may interpret to mean that distinctions based upon mineral or 

 lithological characters are of some real and permanent value in 

 geological classification. The history of development of this 

 system from the first, or Lehmann's system, shows that the linear 

 order of the series of formations in the list is based on the con- 



