92 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



clearness with which he distinguished the leading members of 

 the mountain-system. He established the fundamental dis- 

 tinction of a central chain composed for the most part of 

 primitive rocks, and two lateral zones on the north and on the 

 south of the central chain, composed chiefly of limestone, 

 sandstone, shale, and nagelflue. These leading zones were 

 accurately described with respect to their geographical distri- 

 bution and the various kinds of rock present in them. The re- 

 semblances and differences between the northern and southern 

 zones were pointed out, and the leading stratigraphical features 

 were shown in a number of geological sections. The text was 

 further illustrated by a general geological map of the Alps and 

 several panoramic sketches. A geological map (on small 

 scale) of the mountain-systems of Europe was added for 

 purposes of comparison. 



In describing the Jura mountains, Ebel defined their geo- 

 graphical limits in accordance with their geological structure. 

 He pointed out for the first time that the Swabian and 

 Franconian Alb formed geologically an integral part of the 

 Swiss Jura chain. He also drew special attention to the 

 arched forms of structure as particularly characteristic of the 

 Jura mountains, but failed to find any satisfactory explanation 

 of the curvature of rock-strata. 



The main features of the conformation were thus rightly 

 laid down, but the detailed stratigraphy was less ably handled. 

 Ebel started from the assumption that the whole outer crust 

 of the earth is everywhere composed of the primitive rocks, 

 granite, gneiss, and crystalline schist, and that these rocks have 

 been in certain localities covered by pelagic or terrigenous 

 deposits. He regarded the highly-tilted position of the rocks 

 in the central chain as essentially characteristic of the primitive 

 series, and accepted Alexander von Humboldt's doctrine that 

 the primitive rocks everywhere strike in the same direction, 

 from south-west to north-east. 



In his treatment of the stratigraphical succession in the 

 lateral Alpine zones Ebel attached little weight to the order of 

 rock-formations enunciated by Werner, and considered it far 

 more important to note the sequence of the fossil contents. 

 He pointed out that the strata reposing upon the primitive 

 group contain a few pelagic fossils; in younger strata the 

 remains of marine faunas are much more numerous and varied; 

 in still younger terrigenous deposits there are fossil fishes and 



