XX SUMIMARY OF THE CONTENTS. 



endogenous (granite, sienite, porphyry, greenstone, hypersthene, rockj 

 eupliotide, melapbyre, basalt, and phonolithe); sedimentary rocks (si- 

 lurian schist, coal measures, limestone, travertino, infusorial deposit) ; 

 metamorphosed rock, which contains also, together with the detritus 

 of the rocks of eruption and sedimentary rocks, the remains of gneiss, 

 mica schist, and more ancient metamorphic masses. Aggregate and 

 sandstone formations. The phenomenon of contact explained by the 

 artificial imitation of minerals. Effects of pressure and the various ra- 

 pidity of cooling. Origin of granular or saccharoidal marble, silicifica- 

 tion of schist into ribbon jasper. Metamorphosis of calcareous marl 

 into micaceous schist through granite. Conversion of dolomite and 

 granite into argillaceous schist, by contact with basaltic and doleritie 

 rocks. Filling up of the veins from below. Processes of cementation 

 in agglomerate structures. Friction conglomerates — p. 269 and note. 

 Relative age of rocks, chronometry of the earth's crust. Fossiliferous 

 strata. Relative age of organisms. Simplicity of the first \atal forms. 

 Dependence of physiological gradations on the age of the formations. 

 Geognostic horizon, whose careful investigation may yield certain data 

 regarding the identity or the relative age of formations, the periodic 

 recurrence of certain strata, their parallelism, or their total suppression. 

 Types of the sedimentary structures considered in their most simple 

 and general characters ; silurian and devonian formations (formerly 

 known as rocks of transition); the lower trias (mountain limestone, 

 coal measures, together with todtliegende and zechstein) ; the upper 

 ti'ias (bunter sandstone, muschelkalk, and keuper) ; Jura limestone (lias 

 and oolite) ; freestone, lower and upper chalk, as the last of the flotz 

 strata, which begin with mountain limestone ; tertiaiy formations in 

 three divisions, which are designated by granular limestone, lignite, 

 and south Apennine gravel — p. 269-278. 



The faunas and floras of an earlier world, and their relations to exist- 

 ing organisms. Colossal bones of antediluvian mammalia in the upper 

 alluvium. Vegetation of an earlier world ; monuments of the history 

 of its vegetation. The points at which certain vegetable groups attain 

 their maximum; cycadeae in the keuper and lias, and coniferae in the 

 bunter sandstone. Lignite and coal measures (amber-tree). Deposition 

 of large masses of rock ; doubts regarding their origin — p. 285 and note 



/. The knowledge of geognostic epochs — of the upheaval of mount- 

 ain chains and elevated plateaux, by which lands are both formed and 

 destroyed, leads, by an internal causal connection, to the distribution 

 into solids and fluids, and to the peculiarities in the natural configura- 

 tion of the earth's surface. Existing areal relations of the solid to the 

 fluid differ considerably from those presented by the maps of the phys- 

 ical portion of a more ancient geography. Importance of the eruption 

 of quartzose porphyry with reference to the then existing configuration 

 of continental masses. Individual conformation in horizontal exten- 

 sion (relations of articulation) and in vertical elevation (hypsometrical 

 views). Influence of the relations of the area of land and sea on the 

 temperature, direction of the winds, abundance or scarcity of organic 

 products, and on all meteorological processes collectively. Direction 

 of the major axes of continental masses. Articulation and pyramidal 

 termination toward the south. Series of peninsulas. Valley-like form- 

 ation of the Atlantic Ocean. Forms which frequently recur — p. 285- 

 293 and notes. Ramifications and systems of mountain chains, and tho 

 means of determining their relative ages. Attempts to determine the 

 *enter of gravity of the volume of the lauds upheaved above the level 



