e. Relation of volcanoes to the character of rocks. Volcanic forces form new rocks, and metamorphose the more ancient ones. The study of these relations leads, by a double course, to the mineral portion of geognosy (the study of the textures and of the position of the earth's strata), and to the configuration of continents and insular groups elevated above the level of the sea (the study of the geographical form and outlines of the different parts of the earth. Classification of rocks according to the scale of the phenomena of structure and metamorphosis, which are still passing before our eyes. Rocks of eruption, sedimentary rocks, changed (metamorphosed) rocks, conglomerates -- compound rocks are definite associations of cryctognostically simple fossils. There are four phases in the formative condition; rocks of eruption, p 20 endogenous (granite, sienite, porphyry, greenstone, hyperathene, rock, euphotide, melaphyre, basalt, and phonolithe); sedimentary rocks (silurian schist, coal measures, limestone, travertino, infusorial deposit); metamorphosed rock, which contains also, together with the detritus 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 rapidity of cooling. Origin of granular or saccharoidal marble, silicification 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 doleritic 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 vital 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 'todilegende' and zechstein); the upper trias (butter 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; tertiary formations in three divisions, which are designated by granular limestone, lignite, and south Apennine gravel -- p. 269-278.