GEOLOGICAL HISTORY

Was this change in local, or does it extend to the entire organic world, can not be solved by studying only the area: it is necessary to make observations in the largest possible number and in different localities. Such a comparative study of fossils shows that the distribution of the latter in groups of sedimentary rocks is not accidental and is subject to certain laws: the known remains of living organisms are found in certain strata, and in most cases the order of their successive appearance of the same in different countries. Let us imagine one of those places that are rich rocks containing fossils: fast forward in the Swabian Jura. Marl, clay and limestone in the area, with a remarkable sequence located on each other, contain many fossils, here we find, for example, marls with numerous fossilized shells of ammonites, what are the Ammonites radians and jurensis. Under these marls are shale, they are already different kinds of the same resources, what are the Ammonites communis, heterophyllus and lythensis. Still lie below the layers of limestone with the Ammonites spinatus, followed by clay with Ammonites margaritatus. Investigating such formations in the west and east of the country, we always observe the same sequence of fossils. Observations of similar sedimentary rocks in northern Germany, France and Britain have shown that there are certain in exactly the same manner for the same kinds of fossil animals. Finally, and most remote countries of the world from us in India, America, etc., have repeatedly observed the same sequence in the deposition of sediments containing fossils. From all this it follows that a significant portion of the differences of plant and animal residues, which we observe in the two located on each other strata, caused not by local changes in the organic world, but overall its transformation. Thus, layers of different areas, which contain the same fossils should be assigned to one period. From the sequence of strata, we judged the time of formation of precipitation, the found similar fossils allows us to compare the age strata distant from each other localities. And the whole earth has been found yet where would act in a sequential order is well developed and rich fossil beds of all periods. But since, thanks to fossils, we can compare the rainfall in different countries and determine their age, we can establish a characteristic sequence of precipitation and the found fossils in them, displaying everything in a chronological table in which all education will find its place. The largest division of layers - a group (groupe, Gruppe), then the next unit is called a system (systeme, System), followed by sections (Sections, Abteilungen), subdivided into tiers, or floors (etage, Etagen), which in turn can be divided into substage (sous-etages, Unter-Etagen), or the suites or complexes layers (assises, Schichtencomplexe).