Geology of Peoria County. 19 
lowings of the Labyrinthodon, the yells of the Ichthyosaurus, the piercing 
cry of the long-necked Plesiosaurus, filled the air, and reverberated from the 
wooded shores. 
We stand upon paleozoic ground, while the piled-up strata, as monuments 
of mesozoic and cenozoic time, stand in these other lands, as mementoes of 
times long since garnered into the annals of the dimly visible past. 
ECONOMICAL GEOLOGY. 
In the economical geology of this county, we are most highly favored. 
Nearly all of our territory is underlaid with beds of coal, the united maximum 
thickness of which is about twenty-five feet. This, according to Bousingault’s 
calculation, would make 45,000 tons per acre. Hence, under each farm of 
160 acres, the coal would aggregate 7,200,000 tons! But, the variations in the 
thickness of the beds are such, that we are not warranted in basing our calcu- 
lations upon that amount. I think it safe, however, to assume half that 
thickness as an averoge through the county. Taking this measure, one acre 
of coal, at one cent per bushel, will sum up an amount equal to the present 
value of the surface of the whole farm in most instances. Prof. Worthen 
estimates, that we have an average of seventeen feet under nearly all the 
county. 
Of these coal seams Nos. 4, 6 and 7 are of very easy access; can be worked 
with very little expense, as compared with that of most other countries. 
- An average of three analyses of No. 4 coal gives but 6 per cent. ashes, 
which indicates a greater freedom from earthy impurities than many others. 
An interesting question comes in—What becomes of this carbon we are 
now taking so rapidly from these beds and converting by combustion into 
carbonic acid gas, which passes into the atmosphere? You answer that vege- 
tation takes it. But vegetation seemed to have enough before we began to 
dig it out of the earth. The earth and seas are absorbing a portion by the de- 
composition of vegetable matter, also the direct absorption of the gas, but 
has this increased? It undoubtedly has. The world is converting more than 
three hundred million tons of carbon into gas annually; and yet we can dis- 
cover no perceptible increase of it in the atmosphere. 
Another important item of value isour stone. The sandstone above No. 4 
in the Kickapoo bluffs if properly selected, make as durable building stone as 
any, without exception. That to be selected should be of the ferruginous 
variety, taken out of the quarry late in the autumn, or during the winter, so 
that it will not become dry before the frosts of winter strike it; then, if the 
_ freezing and thawing does not disintegrate the blocks, they can be relied upon 
as equaling any stone that can be found for building purposes. 
Our limestones also are valuable for buildings and making lime. Our sands 
and gravels have their value also. Our clays make a most excellent brick. 
They contain a considerable amount of hydrated oxide of iron, and in burn- 
ing, the water, or hydrogen, is driven off, leaving the peroxide of iron, which 
not only gives the peculiarly reddish color to the bricks, but gives them a 
greater degree of hardness. 
DRIFT, 
The manner in which our clays, sands, and gravels accumulated upon the 
surface, has been a subject of much discussion.. It is now generally conceded, 
however, that they were brought here by the agencies of ice and water. 
There was a time after our series of coal strata were completed, when there 
_ was probably a great uplifting of the surface of the earth, in regions north of 
us. This elevation was so great, that snow and ice accumulated upon it with 
constant persistency. The glaciers were thus formed as a necessary resultant. 
