16 Geology of Peoria County. 
We will now ascend the geological column many thousand feet, to the next 
series. A long time has elapsed; a great gap in our knowledge of the succession 
of life intervenes. The upper Laurentian and Huronian beds have been laid 
down, and ages await the arrival of the new series — the Cambrian. We now 
begin to see life expressed in new and varied forms. But that which existed 
in the lower Cambrian — the Acadian — was all destroyed before the next, the 
Potsdam beds appear. 
In these latter strata, we find a large increase of living forms, and a greater ~ 
variety of species. Of plants are found, however, but one variety, the Fucoids. 
But of the fauna are representatives of the four sub-kingdoms: Protozoan, 
Radiates, Mollusks, and the Articulates. Of the trilobites alone nearly one 
hundred species are described, in this and the next beds. 
Passing up along the line of this column, through the Silurian and Devon- 
ian periods, we are amazed at the records of the works of the Master Builder! 
Fhe remarkable variety and beauty of the forms of life! The immense piles 
of the superstructure; the great power of the oceans as made manifest in the 
history of its building. 
Between the Archaen and Carboniferous periods eleven times has the earth 
been submerged in this county during long intervals, and eleven times has 
she in turn, arisen in her might, and thrown off her watery covering. 
During these perpendicular oscillations of the earth’s surface, the follow- 
ing groups of rocks were formed. Of the lower Silurian the Acadian, Pots- 
dam, Calciferous, Chazy, Trenton and Cincinnati. Of the upper Silurian, the 
Niagara, Lower Helderberg, and Oriskany. Of the Devonian, the Cornifer- 
ous and Hamilton. 
We have now arrived at the Subcarboniferous epochs. We here have five 
groups: the Kinderhook, Chester, Burlington, Keokuk and St. Louis. ‘These 
are the middle ages of the world’s history.””’ The heat of the earth’s surface 
was yet so great, that the carbon in a large measure still floated in the upper 
regions of the atmosphere. But toward the close of this period, it began to 
settle to the earth, ‘‘enveloping it with its dark and noxious gases.” We 
have yet seen few land plants, but now they begin to feed upon this carbon, 
and assume large and beautiful proportions. © 
Air breathing animals “were yet slumbering in the chambers of the future.” 
Quoting from Prof. Winchell: ‘‘In these ages, the shallow sea became a 
marsh, and a foothold for terrestrial vegetation was established. The all- 
adaptive hand of Nature planted the soil with many kinds of herbs and trees. 
Simultaneously on every side innumerable germs spring up from the new- 
made sediments. Vegetation in varied types and family alliances starts forth 
at we fiat of creative energy, and the world is dressqad in a garment of shining 
verdure.” 
COAL FORMATION. 
The carbonic acid so heavily loading the air; the great humidity, and the 
heat stimulated the growth of these plants to a remarkable degree. New and 
beautiful forms were continually appearing. The Calamite, the Ulodendron, 
the Sigillaria, the Lepidodendron (club mosses), the Megaphyton, and many 
other genera with their multiplied species, grew to a great, and constantly 
increasing momentum, until they reached immense proportions. Standing in 
marshes or shallow water, in dense forests, in a soil of rich clay, as they came 
to old age, fell, or were swept down by the tornados of the wilderness, and 
buried beneath the waters at their feet. There they remained in a sound or 
partially decayed condition for centuries. This process of decadence and new 
growth, continued until layer upon layer had been deposited to a depth of 
from ten to fifty or more feet, of compact vegetable matter. It is probable 
that while this was in progress, the ground settled slowly so as to keep the 
material covered with water, which preserved it from decay. 
