lated strain, and the ocean rolled forward, freighted with mud and sand which was spread over the entire vast peat-bed. Thick layers of clay and sand shut up from the atmosphere the expanse of peaty matter which was to consolidate and form coal.

The reign of the ocean was only temporary, and but few centuries elapsed before another change took place. Again occurred a collapse of some stay or support of the earth's crust. The ocean receded, leaving the sea-bottom again exposed to the sunlight. Soon another scene of verdure was spread where the waves of the ocean had so lately tossed. The forests again resumed their work of selecting and storing the impurities of the atmosphere, and soon some adventurous and hardy types of air-breathing animals had made their appearance.

Along the shores of the ocean were exposed headlands from which the older coal formations protruded. Here the waves pounded up beds of sandstone, shale and coal. The sands were deposited along the seashore. The finer and lighter materials were floated away to a quiet retreat in bays and inlets. In a later age, this deposit of coal and clay and particles of decayed wood, became beds of cannel coal.

The land continued to oscillate as long as the atmosphere remained impure. Time after

time, the forest resumed its work, and bed after bed of peat was stored away beneath ocean sediments to await the end. When the work had been accomplished, the forces which had endured the enormous strain that had been accumulating under the prolonged contraction of the interior, yielded with a collapse which shook the entire hemisphere. Massive folds of the huge crust uprose far above the clouds. This was the birth of the Appalachian mountains, and the end of the long Paleozoic Age. Only the bases of those folds remain to-day; but they stand as monuments to the age whose death prepared the world for man and civilization.

Chapter V

C

GAS AND PETROLEUM

ONTRARY to a general belief, petroleum and natural gas are widely distributed.

The drill can scarcely descend for even a few hundred feet in any part of Ohio without giving evidence of the presence of one or both of them. In the three predominant series of rocks, viz.: sandstone, shale and limestone, petroleum is found in varying quantities. The Ohio shale throughout, is petroliferous, and while the percent is small, the aggregate is very large. Prof. Lord, of the State Survey, found but two-tenths of one per cent. of petroleum present in this shale, but some was lost in the process employed.

Estimating the petroleum at two-tenths of one per cent., the amount contained in each square mile of the Ohio shale is three million one hundred and twenty thousand barrels; a larger amount than was ever obtained from any square mile in the Pennsylvania fields. The Lower Helderberg limestone contains approximately, the same amount. While all pervious rocks contain traces of petroleum, sandstones seem best adapted for its subterranean reservoirs.

We will now give some of the scientific facts

governing the formation and accumulation of petroleum :

First. Oil is produced by a chemical change, or a spontaneous disintegration of the substances which formed a part of the oceanic deposits.

Second. Being composed of carbon, hydrogen and oxygen, it must be of organic origin, either animal or vegetable.

Third. As it is lighter than water, it must rise through the water which saturates all rocks. Thus the origin of oil can in no case be at a higher level than where the oil is deposited.

Fourth. A "surface show" of oil is unfavorable as it forebodes leakage; while the accumulation of oil is accomplished by an impervious strata above the reservoir, preventing the "surface show."

Fifth. Petroleum is contemporaneous with the rocks that contain it. It was formed about the time that those rocks were deposited.

Sixth. The situation of the creeks, hills or valleys has no bearing on the distribution of petroleum, hundreds of feet below.

Observation and experience have established the fact that the porous strata in which oil accumulates must have an arched or anticlinal form. The anticline prevents the oil from spreading indefinitely, and causes local accumu. lations or "pockets." Where no anticline oc