AMERICAN" GEOLOGY DECADE OF 1860-1869. 531 



this western area were regarded as belonging " to the most ancient of 

 the Azoic series," and to have been above sea level since very ancient 

 times. As with his predecessors, Kerr was troubled to account for 

 the drift, noting that while it occurred far beyond the limits usually 

 ascribed to glacial action, yet there were " numerous phenomena which 

 have no other plausible explanation." 



Kerr's second report, submitted in 1869, was of equal brevity, but 

 naturally contained more of the results of the author's personal obser- 

 vations. He noted that the mountains, plateaus, and valleys of the 

 French Broad and Lower Catawba areas owed " their existence and all 

 the details of their form and position to the action of water, the basins 

 * * * being * * * without exception, valleys of erosion, hav- 

 ing in no case an anticlinal or synclinal origin." 



The entire western portion of the State he considered as consisting 

 of four groups or formations, first, the— 



Cherokee slates along the Smoky Mountains, on the northwest border, consisting 

 of clay slates and shales, sandstones, grits, conglomerates, and limestones; second, 

 the Buncombe group, occupying the larger portion of the great transmontane pla- 

 teau between the Blue Bidge and Smoky Mountains, and consisting of gneissic and 

 granitoid rocks; third, the Linville slates, a narrow belt stretching for the most part 

 along the Blue Bidge and composed, like the first group, of semimetamorphic argil- 

 laceous slates and shales, sandstones, limestone, and gneissoid grits; fourth, the 

 Biedmont group, gneissic and granitoid. 



He noted further that these four groups constituted two recurrences- 

 of the same rocks, in the same order, recalling Rogers's theory of redu- 

 plication by folding and overturns, as worked out in Pennsylvania. 



John L. Le Conte, a cousin of the Joseph Le Conte, elsewhere 

 noted, is known to science rather through his entomological than geo- 

 logical writings. Five papers are credited to his pen by Darton in his 

 John l. Le Conte's Catalogue and Index of North American Geology. Of 

 Rai'rroad a Jurvey. these, the most important and the only one that need 

 ,867, here be considered is one on the geology of the survey 



for the extension of the Union Pacific Railroad from the Smoky Hill 

 River, Kansas, to the Rio Grande. He made a detailed study of the 

 coal beds, and on the basis of their molluscan remains maintained that 

 such were of Cretaceous age rather than Tertiary, as claimed by 

 Lesquereux. His reasoning as to the relative value of botanical and 

 molluscan remains for determining the age of beds is worthy of note. 

 He wrote: "The difference between the plants of our early Cretaceous 

 and those of the European middle Tertiary could be ascertained only 

 after much discussion and by the stratigraphy of the region, and we 

 have no right from a few resemblances in vegetables to infer the syn- 

 chronism either of the western lignite beds with each other, or any of 

 them with the European Eocene and Miocene, except when supported 

 by paleontological evidence derived from animal remains." In this 

 most geologists will now agree with him. 



