But the great subsidence which had commenced in the Triassic period, along what was to become the future line of the Alpine chain, was continued almost without interruption during the Rhætic, the Jurassic, the Tithonian, the Neocomian, the Cretaceous and the Nummulitic periods. With respect to the strata formed during all these periods, it is found that their thiknesses, which away from the Alpine axis may be measured by hundreds of feet, is along that axis increased to thousands of feet. The united thickness of sediments accumulated along this great line of subsidence between the Permian and Nummulitic periods probably exceeds 60,000 feet, or ten miles. The subsidence appears to have been very slow and gradual, but almost uninterrupted, and the deposition of sediments seems to have kept pace with the sinking of the sea-bottom, a fact which is proved by the circumstance that nearly the whole of these sediments were such as must have been accumulated in comparatively shallow water. [Sidenote: FORMATION OF ALPINE GEOSYNCLINAL.] By the means we have described there was thus formed a 'geosynclinal,' as geologists have called it, that is, a trough-like hollow filled with masses of abnormally thickened sediments, which had been piled one upon another during the long periods of time in which almost uninterrupted subsidence was going on along the Alpine line of weakness in the earth's crust. In this way was brought together that enormous accumulation of materials from which the hard masses of the Alpine chains were subsequently elaborated, and out of which the mountain-peaks were eventually carved by denudation. The third stage in this grand work of mountain-making commenced in the Oligocene period. It consisted of a series of movements affecting the parts of the earth's crust on either side of the line of weakness which had first exhibited itself in Permian times. By these movements a series of tangential strains were produced, which resulted in the violent crushing, folding, and crumpling of the sedimentary materials composing the geosynclinal. One effect of this action was the violent flexure and frequent fracture of these stratified masses, which are now found in the Alpine regions assuming the most abnormal and unexpected positions and relations to one another. Sometimes the strata are found tortured and twisted into the most complicated folds and puckerings; at others they are seen to be completely inverted, so that the older beds are found lying upon the newer; and in others, again, great masses of strata have been traversed by numerous fractures or faults, the rocks on either side of which are displaced to the extent of thousands of feet.