The science of life : fully illustrated in tone and line and including many diagrams

THE EVIDENCE OF THE ROCKS

Ruy

| i hy a a : ty ee ee

Hh os i : Saat UA Na Thy \

i Hi

PES PARISI“US-

eee

Fig. 121.

When the remains here shown were unearthed in 1726, they were described by Professor

Scheuchzer of urich, who published this figure of them, as “‘ the damaged skeleton of a poor sinner drowned in the Deluge.”

As a title to the picture is written ‘‘ Homo Diluvii Testis *’—man, witness of the Deluge.

A century later Cuvier showed

the remains to be those of a giant Salamander, now called Andrias scheuchzeri ; it came from strata of Miocene Age (V C) in Baden.

they would gladly do, for the ease and comfort of their readers.

We will, however, attempt something that may be of service to those who find these names of Eras and Periods too clumsy a load to carry in their memories. We will attach numbers and letters to these Eras, Periods, and sub-periods, Roman numerals for the Eras, letters for the Periods, and Arabic numbers for sub-periods. These numbers we will append to the names as they crop up in what follows, and at the price of a certain typographical disfigurement the reader will be reminded of the position of each Age as it is named. Thus, Archeozoic is I, Proterozoic II, and the Paleozoic Era III. The two former we do not subdivide for our purposes. But III falls into divisions, Cambrian (III A), Ordovician (III B), Silurian (III C), Devonian (III D), Carboniferous (ILE), and Permian (III F). Each of these can be further divided into Lower (1), Middle (2), and Upper (3). Upper Carboniferous, for example, is III E 3. IV stands for the great Era of the Mesozoic, with its divisions, Triassic (IV A), Jurassic (IV B), and Cretaceous (IV C). Finally, most modern of all, our present Era, the Cenozoic, is distinguished by V. That again subdivides into Eocene (V A), Oligocene (V B), Miocene (V C), Pliocene (V D), Pleistocene (V E), and the current Period, the Recent (V F). With the help of the printer’s

reader these numbers shall as a rule appear after each repetition of these geological names.

We may add one further word of elucidation. In the earlier days of geology only three great Eras were distinguished instead of the five we recognize now. ‘These were called Primary, Secondary, and Tertiary. Primary was our Archeozoic (I), Proterozoic (II), and Paleozoic (III) together, Secondary was what we now call Mesozoic (IV), and Tertiary, the Cenozoic (V). Later a fourth term Quaternary was added to distinguish the most modern deposits—those now called Pleistocene (V E) and Recent (VF). The word Primary is now rarely used, but Secondary and Quaternary turn up at times, and Tertiary (because it is an easier word, perhaps) has more than held its ground against Cenozoic. The reader is likely to find us falling rather frequently into the use of that more familiar word.

In column 3 of our diagram the maximum thickness of the layers is given, Period by Period. Of course, the total thickness, or anything like it, is not to be found piled up at any one spot of the earth’s crust, but the total thickness gives a rough measure of the time taken to lay down these miles of rock, film upon film, year after year. ‘The time must evidently have been prodigious ; and when we look at the actual figures in years (which are determined by another method,

197