I. GENERAL STRUCTURE. The great central axis of the Alpine region, stretching from the Rhone to the Danube, consists mainly of the primary crystalline rocks. The granite is everywhere accompanied by gneiss, mica-schist, chlorite-schist, silicious and serpentine limestones. The upper silurian, devonian, and carboniferous systems are distinctly represented in the eastern Alps; but no traces of the Permian deposits have been detected in them or in any part of southern Europe; while again in following the central parts of the chain from Austria into Switzerland and Savoy, all fossil evidences of the four sedimentary systems disappear. The conclusion arrived at by geologists, therefore, is that for these palæozoic and triassic formations there exist no representatives among any of the vast piles of strata of the western Alps; or, if they ever had a place in this part of the chain, that they have been obliterated by the powerful transmuting action of metamorphism, or plunged to inaccessible depths beneath the upraised edges of the primary series. Coal plants, and anthracite coal itself, have both indeed been found in the valley of the Arve in Savoy, at Tarentaise, Maurienne, and along the base of Mont Blanc; but as they occur in connection with belemnites, these beds have been referred by M. E. de Beaumont and others to the Lias formation, which is clearly determined by its numerous animal fossils to exist in this part of the chain. The remarkable picturesque rocks of Varennes, Duron, and the Col de Balme belong to the lias deposit—the grandest specimens, perhaps, of natural architecture anywhere to be seen. But, making allowance for all the uncertainties of their lithological complement, and quitting all points of a doubtful character, it has been satisfactorily established that the flanks of the Swiss Alps are covered by a series of sedimentary deposits of vast thickness, which form a true transition from the newer secondary into the older tertiary strata. The normal arrangement of rocks within these limits is complete, beginning with the lias and terminating in distinctly recognized beds of the tertiary pleiocene group.