vegetable matter, the remains of coniferous forests that occupied the country before the advent of the drift, or at some interglacial stage of its duration. Peat bogs are sometimes found buried in like manner in or under the bowlder clay. The deposits of latest age in this great series consist of stratified clays, sands and gravels. The maximum thickness of drift beds that has thus far been found in the State is 530 feet. This measurement was obtained from Saint Paris, Champaign county. Depths of 300 and 400 feet are no longer unusual. The average thickness of these accumulations in Northwestern Ohio exceeds 100 feet. They exercise a controlling influence upon the relief, drainage, soils and water supply of the regions which they occupy. They have filled the valleys of earlier drainage systems and in many cases have obliterated all traces of their existence, thus restoring to large portions of the State the uniformly level surface which prevailed in them when they were first elevated above the waters of the

ocean

The bowlder clay or till is filled with bowlders of northern origin, derived from the highlands of Canada and intervening districts. Some of them contain 2,000 cubic feet above ground. They can in many cases be referred to particular localities and sometimes to particular ledges from a score of miles to 400 miles distant.

The stratified drift contains vast accumulations of sand, gravel and clay, all of great economic value. Brick clays of good quality are everywhere accessible. These stratified beds constitute a natural filter for surface water to a great extent. The rainfall descends slowly through them until the impervious bowlder clay is reached. The depth of the surface of this last named deposit, in large areas of the State, determines the depth of the ordinary wells of these areas. Sometimes, however, a water supply is derived from seams of sand and gravel within the bowlder clay or immediately below it. Such a supply is to quite an extent protected from surface impurities.

The terminal moraine that marks the boundary of the glacial deposits is fairly distinct throughout the State. Soils and vegetation unite to emphasize it, as well as special accumulations. passes through the counties of Columbiana, Stark, Wayne, Richland, Holmes, Licking, Fairfield, Ross, Highland, Adams and Brown, crossing the Ohio river into Kentucky from the latter county but returning to the north side of the river again in Southeastern Indiana. As a result of this temporary obstruction of this great water way it has been pointed out that the waters of the Ohio must have been dammed back so as to form a large lake, including the valley proper and its tributaries as far at least as Pittsburg. The barrier appears to have given way in such a manner as to reduce once and again the level of the intercepted waters abruptly. Such a mode of retreat, at least, would explain the succes

sive terraces that border the main streams at the present time.

II. GEOLOGICAL STRUCTURE. The geological scale of the State has now been briefly treated. An equally brief account must be added of its structure. By this term is meant the present arrangement or disposition of the strata as effected by all the movements of the earth's crust in which they have had a part, and by which they may have been bent into arches or troughs or left in terrace-like monoclines.

The geological structure of Ohio is as simple as that of almost any other 40,000 square miles of the earth's surface. All of its strata except a small portion of the coal measures were deposited in the waters of an ancient arm of the sea, of which the present Gulf of Mexico is the dwarfed and diminished remnant and representative. Its most fossiliferous limestones, as the Corniferous, for example, stand for clear waters of tropical warmth. Its conglomerates and sandstones required strong currents for their transportation from distant shores. Its shales must have been deposited in seas of at least moderate depth, large areas of which, as well as all of the shores, were covered with sargasso-like masses of sea-weed.

These strata seem to have been deposited on a fairly regular and level floor, and they have never been subjected to very great disturbance; that is, they have nowhere been raised into mountains nor depressed into deep valleys, but still they have been warped and distorted to some extent in the course of their long history.

The Cincinnati Anticlinal.

As soon as the geology of the Mississippi valley began to be studied, it became apparent that there had been in early time an extensive uplift of the older rocks in the central parts of Tennessee and Kentucky and in Southwestern Ohio, which had exerted a profound influence on all the subsequent growth of the regions traversed by and adjacent thereto. This uplift has received several designations, but the name given to it by Newberry, viz., the Cincinnati anticlinal, will here be adopted, inasmuch as this geologist has furnished by far the most careful and connected account that has yet been given of it.

It is to be recognized, however, that this structural feature has in it little or nothing of the character of an anticlinal or arch, as these terms are commonly understood. There is no roof-shaped arrangement of the strata whatever, but they are spread out in a nearly level tract, 100 miles or more in breadth. The slopes within the tract are very light, and are quite uniform in direction, and the boundaries of the tract are well defined, as a rule.

The Trenton limestone, as has already been shown, makes the floor of Western Ohio. By means of the deep drilling that is now in progress throughout this part of

the State we have obtained soundings to this limestone floor so extensive that we are already able to restore approximately its topography.

This underground disposition of the Trenton limestone becomes very significant in connection with the Cincinnati uplift. In fact, it is the Cincinnati uplift; and the study of the facts pertaining to it will be found to throw more light on this earliest and most important structural feature of the State than can be obtained from any and from all other sources. The results are altogether unexpected.

It appears that in Lower Silurian time a low fold, extending in a general northeast direction, entered Ohio from the southward and continued its advance across the State during immense periods of time. It has heretofore been believed that the fold as it extended across the State held its original northeasterly direction, but it now becomes evident that in its earlier stages in Ohio it advanced to the northwest instead, extending into Northern Central Indiana, so far as its main body was concerned. From this point an off-shoot of smaller area was directed into Ohio, the boundaries of which are found to be very irregular, and in connection with which some surprising facts in Ohio geology have come to light. With these same facts extraordinary economic interest has been found to be associated.

The easterly or southeasterly dip of the rocks that begins at the margin of the tract, now described as the Cincinnati axis, continues through the subsequent history of the State, and constitutes the most important physical feature of its geology. All of the Subcarboniferous and Coal Measure strata, in particular, are affected by it. The southerly element of it gradually increases as we pass to Northeastern Ohio, and it is probable that the dip becomes due south at some points in this portion of the State. Beyond the limits of Ohio, in Pennsylvania and West Virginia, the corresponding strata descend sharply toward the westward. These facts considered together mark out the limits of the arm of the sea in which, and around which, the northern extension of the Appalachian coalfield was built up, the Cincinnati axis forming its western boundary. These uniform and continuous southeasterly dips can be explained by the steady growth of the land to the westward, after the fashion already described. The dip is at right angles to the constantly advancing border of the sea. It seldom exceeds thirty feet to the mile, or but little more than half of one degree, in the large way, but it is alternately sharpened and reduced, so that for short distances a much greater fall, or much less, may be found.

The facts of our present topography seem to point to an original equality of elevation of those portions of the State that were successively brought under this uplifting force. The western outliers of all of the formations are, at the present time at least, at approximately the same elevation above the sea.

The statements already made as to the exceeding regularity of the geological structure of Ohio need no qualification, but this regularity of the State, as a whole, is not inconsistent with the existence of a few minor folds and arches, distributed especially through the eastern half of our territory.

In the southeastern quarter are a few anticlinal arches, all of which, however, are very gentle and low, and none of which can be traced for many miles in the direction in which they extend. They involve all of the strata that belong in the district in which they are found. A modification of the arch resulting in a terrace-like arrangement of the strata is one of the most important phases of the structure in this portion of the State. Among the arches, all of which are very feeble, the Fredericktown and Cadiz arches, which are probably one and the same, may be named, and also the Cambridge anticline. The Macksburg oil field affords an excellent example of the terrace structure.

To sum up the statements now made, we know but comparatively few arches in Ohio, and these few are moderate in slope and small in height. Fuller knowledge of our geology will doubtless give us a larger number of these low folds, but there is little probability that any sharp and well-defined anticlinals have altogether escaped notice. Those that remain to be discovered will agree with those already known, in breaking up the monotony of our series by the suspension or occasional reversal of the prevailing dip and in requiring close and accurate measurements for their detection.

By untrained observers, the water-sheds of our drainage channels are often mistaken for anticlinals. If anticlinals traverse the series where these identifications are made, they may well serve to divide the drainage systems from each other, but such "divides" do not by any means require these structural accidents as the conditions on which they depend. Anticlinals must be demonstrated, not inferred.

There are but few districts known in Ohio in which disturbances are to be found that fairly deserve the name of fauits. In the northeast corner of Adams county, and in adjacent territory, there are a number of square miles throughout which the strata are really dislocated. The Berea grit is found in contact with the Niagara shale in some instances. The throw of such faults must be at least 400 feet. Faults of this character in Ohio geology are as unusual and unexpected as trap dykes in Northern Kentucky, the latter of which have been recently reported by Crandall.

III. PETROLEUM AND NATURAL

GAS.

These subjects, and especially the latter, have recently acquired such widespread interest and importance in the country that a separate section will here be given to their consideration.

The introduction of natural gas on the

large scale is of comparatively recent date. It was begun in Pittsburg and in the region around it a dozen years since, but it is only within the last six years that it has made a deep impression upon the country at large.

The cheapness of the new fuel, the economy resulting from several different factors in its use, the improvement of product in a number of lines of manufacture, all combine to give a decided advantage to the centres that have been fortunate enough to secure it, and to make competition seem almost hopeless to the towns that are without it.

In consequence, an earnest and eager search for natural gas has been begun throughout entire States, and vast amounts of money have been used in carrying forward these explorations. Next to Western Pennsylvania Northwestern Ohio has scored the most signal success and, following the experience of Ohio, Eastern Indiana has also found one of the most valuable fields of the country.

The production of petroleum and gas in Ohio will be briefly described in this section, but, preceding this description, a few statements will be made as to the theories of origin and accumulation of these substances which seem best supported.

ORIGIN OF PETROLEUM AND Gas. It is not necessary to consider the origin of natural gas and petroleum separately. They have a common history. They are produced from the same sources, accumulated by similar agencies, and stored in the same reservoirs. In order of formation, petroleum is probably first. It is the more complex in composition and thus nearer to the organic world from which it is derived. Gas is the same substance on the downward road to the simplicity of inorganic compounds. No process is known by which gas is built up into oil, but the breaking up of petroleum into gaseous products is seen to be constantly going forward in nature, and it is also effected in the large way artificially.

Petroleum never exists free from gas, but it is sometimes asserted that gas is found that has no connection with petroleum. This claim is probably a mistaken one, and if the dryest gas could be followed throughout its underground reservoirs, it is altogether probable that accumulations of oil would be found along the line in every case. There is no horizon known that produces either substance to the entire exclusion of the other.

As already implied, petroleum and gas are derived from the organic world. Both vegetable and animal substances have contributed to the supplies, and these separate sources give different characters to their products, as will be presently shown. There are certain other theories in regard to the origin of petroleum, it is true, which have been advanced by eminent chemists, but which do not match at all well with the geological facts involved. These last-named theories refer petroleum to peculiar decompositions and recompositions, chiefly of water and carbonic acid, which are supposed to be carried on at considerable

depths in the earth, where these substances are brought into contact with metallic iron or with the metallic bases of the alkalies at high temperatures. Never were more artificial or unverifiable theories presented for the explanation of natural phenomena, and it is surprising that they should have obtained any currency whatever. Something might be said for them, perhaps, if we had no other possible way of accounting for the facts to which they refer, but when they are compared with the theories of organic origin they have no standing ground. The truth is, we are constantly manufacturing from animal and vegetable substances in the large way, both gas and oil that are fairly comparable in both chemical and physical_characteristics, with the natural products. Further, we find vegetable substances passing by natural processes into petroleum and allied compounds, so that there is no need whatever to invent a strained and fantastic theory based on remote chemical possibilities, in order to cover the ground. These chemical theories teach that the process of oil and gas formation is a continuous one, and no reason is apparent why stocks may not be maintained from such a source even when they are drawn upon. Perhaps it is this feature that has recommended these theories more than any other. Any doctrine that gives us unwasting supplies of force is sure to be popular as long as it can find the semblance of justification, as witness the hold that the claims for perpetual motion have on the public mind.

The petroleum and gas of shales and sandstones are in the main derived from vegetable matter, and as the principal stocks are found in sandstones, vegetable matter may be said to be the chief source. The oil and gas of limestones are presumably derived from animal matter, inasmuch as the limestones themselves are known to be, in the main, a product of animal life.

The vegetation principaily employed in this production is of the lower kinds, seaweeds and other allied groups being altogether the most conspicuous elements. The animal life represented in limestone oil and gas is also of the lower groups. Plants may have been associated also with animal matter in the formation of limestone oil, to some extent.

HOW WAS PETROLEUM FORMED? To the question, How were these bodies formed out of organic matter? there are various answers.

They are most commonly referred to the agency of distillation. Destructive distillation consists in the decomposition of animal or vegetable substances at high temperatures in the absence of air. Gaseous and semiliquid products are evolved, and a coke or carbon residue remains behind. The "high temperatures" in the definition given above must be understood to cover a considerable range, the lower limit of which may not exceed 400 or 500 degrees F.

Petroleum and gas on the large scale are

not the products of destructive distillation. If shales, sandstones, or limestones holding large quantities of organic matter, as they often do, and buried at a considerable depth, should be subjected to volcanic heat in any way, there is no reason to doubt that petroleum and gas would result from this action. Without question, there are such cases in volcanic districts, but the regions of great petroleum production are remarkably free from all igneous intrusions, and from all signs of excessive or abnormal temperatures. All claims for an igneous origin of these substances are emphatically negatived by the condition of the rocks that contain them.

There is a statement of the distillation theory that has attained quite wide acceptance, which needs to be mentioned here. It is to the effect that these substances, oil and gas, have resulted from what is called "spontaneous distillation at low temperatures," and, by low temperatures, ordinary temperatures are meant. It does not, however, appear on what facts in nature or upon what artificial processes this claim is based. Destructive distillation is the only process known to science under the name of distillation, which can account for the origin of oil or gas, and this does not go on at ordinary or low temperatures. A process that goes on at ordinary temperatures is certainly not destructive distillation. It may be chemical decomposition, but this process has a name and place of its own, and does not need to be masked under a new and misleading designation, such as spontaneous distillation. No help can come to us, therefore, from the adoption of the spontaneous distillation theory.

It seems more probable that these substances result from the primary chemical decomposition of organic substances buried with the forming rocks, and that they are retained as petroleum in the rocks from the date of their formation. It is true that our knowledge of these processes is inadequate, but there are many facts on record that go to show that petroleum formation is not a lost art of nature, but that the work still goes on under favorable conditions. It is very likely true that, as in coal formation, the conditions most favorable for large production no longer occur, but enough remains to show the steps by which the work is done.

The spontaneous distillation" theory has probably some apparent support in the fact that must be mentioned here, viz. that where petroleum is stored in a rock, gas may be constantly escaping from it, constituting, in part, the surface indications that we hear so much of in oil fields. The Ohio shale, for example, is a formation that yields along its outcrops oil and gas almost everywhere, but no recent origin is needed for either. The oil may be part of a primitive store, slowly escaping to the day, and the gas may be constantly derived from the partial breaking up of the oil that is held in the shales. The term "spontaneous distillation" might, with a little latitude, be applied to this last-named

stage, but it has nothing to do with the origin of either substance.

While our knowledge of the formation of petroleum is still incomplete and inadequate, the following statements in regard to it are offered as embodying the most probable view :

1. Petroleum is derived from vegetable and animal substances that were deposited in or associated with the forming rocks.

2. Petroleum is not in any sense a product of destructive distillation, but is the result of a peculiar chemical decomposition by whic the organic matter passes at once into this or allied products. It is the result of the primary decomposition of organic matter.

3. The organic matter still contained in the rocks can be converted into gas and oil by destructive distillation, but, so far as we know, in no other way. It is not capable of furnishing any new supply of petroleum under normal conditions.

4. Petroleum is, in the main, contemporaneous with the rocks that contain it. It was formed at or about the time that these strata were deposited.

THE DISTRIBUTION OF PETROLEUM AND GAS.

The

Contrary to a commonly received opinion, petroleum and gas are very widely distributed and very abundant substances. The drill can scarcely descend for even a few hundred feet at any point in Ohio, without showing the presence of one or both of them. The rocks of the State series can be roughly divided into three great groups-limestones, sandstones and shales. Petroleum is found abundantly in each of these groups. percentage is small, but the aggregate is large. It is equally, or at least generally diffused throughout certain strata, while in others it is confined to particular portions or beds. An example of the first case is found in the Ohio shale. The Ohio Shale, Cleveland-Erie-Huron, of earlier reports, consists of a series of homogeneous, fine-grained deposits, black, blue and gray in color, 300 feet thick on their western outcrop in Central Ohio, but more than 1,800 feet thick under cover in Eastern Ohio. This entire formation is petroliferous, as is proved by an examination of drillings that represent the whole section. The black bands are probably most heavily charged. The chemist of the survey, Professor N. W. Lord, finds two-tenths of one per cent. of petroleum, as such, present in these bands, and is certain from the nature of the processes that he was obliged to employ that the entire amount is not reported. But, estimating the percentage to be but one-tenth of one per cent. in place of two-tenths, and calculating the thickness of the shale at its minimum, viz., 300 feet, we find the total stock of petroleum held in the shale to be 1,560,000 bbls. to the square mile, or nearly twice as large amount as has ever been obtained from any square mile of the Pennsylvania fields.

Of the limestones of the State the Water

lime, or Lower Helderberg limestone, is probably the most heavily and persistently charged with petroleum. Drillings taken from this stratum, at a depth of 400 to 500 feet below the surface in the trial-well lately sunk at Columbus, are found by Professor Lord to have the same amount of free petroleum that the black shale contains, viz., two-tenths of one per cent. The limestone also has the same thickness that is assigned to the shale on its outcrop, viz.. 300 feet. The figures, therefore, duplicated those already given. The total amount of oil from these two sources exceeds 3,000,000 bbls. to the square mile.

All the other great limestones of our series carry petroleum, at least in certain beds. The Clinton limestone is often an oil-bearing rock, and the show of its outcrop has led to the sinking of a number of wells in search of oil, in past years. The Niagara limestone is highly bituminous in places. Asphaltic grains, films and masses constitute as much as 4 or 5 per cent. of its substance at several points in the State. The Corniferous limestone is also distinctly bituminous in some of its beds. The limestones of the Cincinnati group also carry a determinable amount of petroleum.

As for sandstones, all know that it is in them that the main stocks of petroleum have thus far been found, but there is good reason to believe that these stocks are not native in the sandstones, but have been acquired by them subsequent to their formation. This point will be considered further, under another head.

MODES OF ACCUMULATION OF PETROLEUM AND GAS.

In the accumulation of petroleum, two stages are to be noted, viz.: a primary and a secondary stage. The first is concerned with the retention of petroleum in the rocks, and might have been with equal propriety treated under the preceding head. The second stage is concerned with the origin and maintenance of the great stocks of oil and high-pressure gas, in which all the value attached to these substances lies. Both are connected with the composition of the rock series in which oil and gas are found, and the latter is also greatly affected by the arrangement and inclinations of the rock masses, or, in other words, by their structure.

The primary accumulation of petroleum, or its retention in the rocks in a diffused or distributed state, seems to be connected with the composition of the series to a great degree. The great shale formation of Devonian and Subcarboniferous ages that separates the Berea grit from the Devonian limestone, the western edge of which shale formation outcropping in Central Ohio is know as the Ohio shale (Cleveland, Erie, Huron), is unmistakably the source of the greatest accumulations of oil and gas, so far found, in the country. It holds thus far, as decided, a superiority to all other sources, as the Appalachian coal-field does to all other sources

of fossil fuel. The accumulation of petroleum in this great shale formation is no accident. It depends on two factors, viz. the abundance of vegetable matter associated with the shales in their formation, which is attested by the large amount still included in them, and upon the affinity of clay for oil. The last-named point is an important one. Clay

has a strong affinity for oil of all sorts, and absorbs it and unites with it whenever the two substances are brought into contact. Professor Joseph Leidy made the interesting observation a number of years since, that the bed of the Schuylkill river in Philadelphia, below the gas works, was covered with an accumulation of the oily matters that are always formed in the process of gas-making. As these substances are lighter than water and float upon its surface naturally, it was at first sight hard to understand how they could have been carried to the river bed, but it was soon learned that the clay of the river water absorbed the oils as they were floating along. and finally sank with them to the river floor. In a similar way we may suppose the primary accumulation of petroleum in the shales to have been in part accomplished. The oil set free by vegetable decomposition around the shores or beneath the waters of a sargasso sea, would be arrested by the fine-grained clay that was floating in the water, and would have sunk with it to the sea floor, forming this homogeneous shale formation that we are now considering. Sand would have no such collecting power.

The distribution of petroleum through limestone is not as easily explained, but it may be in part dependent on the presence of the same element, viz., clay. In almost all limestones there is a percentage of clay present, and frequently it rises to a conspicuous amount. Oil is held in both magnesian limestones and in true limestones in Ohio. magnesian limestones are largely in excess in the series of the State, and it so happens that all of the most petroliferous strata are magnesian in composition, but this fact is probably without significance in this connection.

The

Petroleum distributed through shales or limestones in the low percentages already named, although the total amount held may be large, is of no economic value. Like other forms of mineral wealth, it must be concentrated by some natural agencies before it can become serviceable in any way. This brings us to consider the secondary accumulation of petroleum already referred to, by means of which all the great stocks have been formed and maintained. This constitutes one of the most important subjects in the entire history. of petroleum. The sources of oil and gas are very widespread, as has already been shown, but the concentrated supplies are few and far between. To learn the horizons and locations of these supplies is the condition of most successful operations in the production of oil and gas, and it is in this field that the most important practical applications of geology to these subjects are to be found.