North America

Besides the concentration of carbon in plant and animal tissues and its change to hydrocarbons, there is a still further concentration necessary in order that stores of petroleum, gas, etc., shall be accumulated so as to be of economic value. This accumulation is dependent largely on physical conditions. The production of hydrocarbons from organic matter contained in sedimentary rocks, and particularly in shale, is going on in many regions, and probably nearly everywhere, especially when the soft parts of animals are buried in the rocks, but the petroleum, gas, etc., generated escape at the surface and pass into the air and are again widely disseminated, unless conditions are present which lead to their accumulation. The conditions favouring the natural storage of the substances referred to are cavities, or more usually porous beds, such as sandstone, beneath impervious beds, such as clay or shale. The conditions are still more favourable when lateral as well as vertical escape is cut off, as, for example, when arches or domes occur. The most favourable conditions result when a bed of shale or other rock, as a, Fig. 35, from which hydrocarbons are being evolved occur beneath a sheet of porous sandstone or fissured rock of any kind, b, above which there is a close-textured, unfractured stratum, such as shale, c, and the series is bent along certain axes into upward folds or anticlinals. Under these conditions, as extended experience has shown, a well drilled at d should yield in succession gas, petroleum, and water.

The conditions for the production of petroleum, gas, etc., have been present on the earth since the first appearance of life, and reservoirs may have originated at any subsequent time. The oldest known reservoirs still charged with these substances that have been discovered occur in the earlier Paleozoic rocks, just above the formations containing the oldest known fauna. Important petroleum and gas fields in rocks of the Trenton period occur in New York, Ontario, Ohio, and Indiana. The Devonian rocks of Pennsylvania, New York, Ontario, etc., also yield large supplies of both oil and gas. Mesozoic rocks of Colorado, Wyoming, etc., are also rich in the concentrated hydrocarbon referred to, and on the Pacific coast, particularly in California, rocks of Cenozoic age are highly productive. Petroleum and gas may occur also in rocks more recent than the Cenozoic, but owing to the absence of reservoirs, and possibly the lack of sufficient time, no important accumulations are known in beds more recent than the Tertiary, unless they come from a deeper source in older rocks. The vast quantity of petroleum stored in the rocks of various ages in North America is indicated by the fact that in 1900 the yield from the wells of the United States was 63,362,704 barrels, and from Canadian wells about 280,000 barrels, making a total of nearly 64,000,000 barrels.

The stores of rock-gas are also enormous, as is indicated by the fact that a single well at Bairdstown, Ohio, yielded over 17,000,000 cubic feet per day. In 1890 the average daily flow of the Indiana gas-wells was 779,525,000 cubic feet. The value of the natural gas consumed in the United States in 1900 was $23,606,463.

In the sedimentary rocks of North America there occur also extensive and valuable deposits of semifluid and solid hydrocarbons, such as maltha, asphaltum, albertite, grahamite, uintahite, etc., which have arisen, under the most plausible explanation thus far offered, from the concentration by evaporation of fluid hydrocarbons such as petroleum. The evaporation, particularly of heavy petroleum, leads to the formation of a solid residue, similar to asphaltum. In fact, there is no definite boundary between the lightest naphtha and the most coal-like asphaltum. They form a connected hydrocarbon series, analogous to the coal series.

Albertite, a bright, coal-like substance, exceedingly rich in volatile hydrocarbon, occupies fissures in Carboniferous rocks in Nova Scotia, and a similar but less lustrous mineral, termed grahamite, occurs in fissures in rock of the same age, near a rich oil-pool in West Virginia. Other similar deposits, but usually wax-like and dull, are found in Utah and neighbouring States. Asphaltum occurs in vast quantities in southern California, and also in Cuba; these deposits resemble the celebrated asphaltum of Trinidad and give promise of being fully as extensive and valuable.

In brief, gaseous, fluid, semifluid, and solid hydrocarbons in great variety are widely distributed throughout the portions of North America where the surface is composed of sedimentary beds, and in a few instances occur in cavities in igneous rocks as well.

The influence of life in leading to the concentration of substances of commercial value is still further illustrated by the beds of diatomaceous earth which are found in various portions of North America and elsewhere, particularly in Cenozoic and more recent terranes. Beds of diatomaceous earth reported to be 40 feet thick and of wide extent have been found near Richmond, Virginia, and similar deposits occur at several localities in Oregon, California, etc. The uses of this fine, white, flour-like powder, each minute grain of which is a beautiful siliceous organism, are for polishing powder, as an ingredient in friction soap, as an absorbent for nitroglycerine in the manufacture of high explosives, etc.

A class of substances of economic importance which owe their accumulation to chemical agencies acting at the surface of the earth is well illustrated by deposits of rock salt and gypsum.

In the Silurian system in New York, Ontario, Michigan, etc., several beds of rock salt and gypsum occur, indicating that there were formerly a number of separate evaporating basins in that region. The beds of salt vary in thickness from a few inches to over 300 feet, as at Tulley, New York. At Goodrich, Ontario, 6 beds of salt from 6 to 35 feet thick have been penetrated in a single well. With the salt in this the Salina formation there are many beds of gypsum. In rocks of Carboniferous age in Michigan, other extensive beds of salt and gypsum have been discovered. In Louisiana, Texas, Utah, and other States, salt and gypsum occur in Mesozoic and Cenozoic rocks. One of the most remarkable of these deposits is beneath small islands in the Gulf of Mexico off the Louisiana coast. On Jefferson Island, for example, rock salt was reached recently at a depth of 260 feet beneath Cenozoic rock, and was penetrated for over 1,800 feet without reaching the base of the deposit. The supply of salt stored in the rocks, and the natural brines of the arid region, such as the waters of Great Salt Lake, afford an inexhaustible supply upon which comparatively small demands have thus far been made.

In addition to salt and gypsum there are other substances that have been accumulated in a similar manner, such, for example, as sodium sulphate, of which large beds occur in the desiccated lake basins of the arid region, sodium bromide, which is obtained from some of the ancient brines pumped from deep wells in Michigan.

Next to the fossil fuels, the most important products of the rocks in North America are the iron ores. Although certain igneous rocks are rich in iron, and in some instances contain it even in a pure or metallic state, none of the rocks that have cooled from fusion carry iron in any form in sufficient quantities to be of commercial importance. Most of the iron in igneous rocks is contained in mineral, usually silicates, and would be difficult to separate. When exposed to the air and to percolating water, the iron-bearing minerals of the igneous or other rocks decay and the iron enters into various new combinations. When organic acids are present, and especially carbon dioxide, ferrous carbonate is formed, which is quite soluble, and is taken into solution by percolating water, some of which emerges as springs, and joins the surface run-off, which may also take up ferrous carbonate in solution. One of the most common methods by which iron ore is accumulated is when water carrying ferrous carbonate in solution forms swamps and lakes, and in many instances as the water is exposed to the air and aided by evaporation it parts with a portion of its carbon dioxide, and the hydrated sesquioxide of iron or limonite results. When, under similar conditions, an excess of organic matter is present, beds of ferrous carbonate are formed. In other instances iron oxide is precipitated in swamps and lakes through the action of low forms of plant life. The ores of iron concentrated in these ways are in many instances in well-defined layers, or lenticular bodies, which are thickest in the central portion and thin out in all directions. Their forms are determined mainly by the shapes of the depressions they occupy. Both ferrous carbonate and limonite, however, occur in irregular surface deposits.

In North America, bog-iron ores occur at the surface in many regions, in existing swamps and about springs, but are seldom of economic importance, owing in part to the great abundance of better ores. Limonite occurs at the surface also, having been deposited in cavities and as a cement for loose fragments, particularly on the weathered outcrops of formations rich in iron. When rocks contain but a fraction of 1 per cent of iron, the soil on their weathered outcrops, owing to the removal of the more soluble ingredients and the leaving of the less soluble oxidized iron, have a yellow, brown, or red colour, and in some instances this process of concentration has produced workable iron ore. Limonite and earthy hematites occur widely throughout the Appalachian region, in central New York, and westward to the Mississippi Valley. One of the most productive formations is the Clinton, a division of the Silurian, the outcrop of which extends in a nearly continuous band from Alabama, where at Birmingham, etc., it is extensively worked, northward along the west side of the Appalachians to central New York, and thence westward to Ohio, and appears again in Wisconsin. At many localities throughout this belt, some 1,300 miles in length, iron furnaces have been built, although now mostly abandoned, the ore supply being the weathered outcrop of the Clinton limestone.

In the Carboniferous rocks of Pennsylvania and neighbouring States to the south and west, layers of ferrous carbonate, formed when there was an excess of organic matter present, termed black-band ore and kidney ore, occur. The former is present as regular strata and the latter in oval concretionary masses. These ores, although not as rich in iron and less pure than certain other and more abundant and more accessible deposits, have been extensively utilized, largely for the reason that they occur in the same formation which furnishes coal available for their reduction.

Deposits of iron ore accumulated in the several ways referred to above may be metamorphosed and changed to hematite and magnetite. The richest iron ores of North America are of this nature, and will be referred to below in connection with other substances of economic importance contained in the metamorphic rocks.

There are various other substances in the stratified rocks of North America of economic importance which owe their value to some process of concentration. Certain rocks, as the so-called greensands or marls of eastern New Jersey, contain from 3 to 10 per cent of potash, which makes them valuable fertilizers. In this instance the concentration took place on the floor of the sea, through the action of decomposing organic matter, and the potash-bearing mineral of the greensand, namely, glauconite, was deposited in the interiors of the minute tests of foraminifera. The importance of this material is indicated by the fact that the greensands of New Jersey have been actively worked for more than half a century, the annual products during many years being upward of 100,000 tons.

Extensive areas in the Carolinas, Florida, etc., underlaid by rocks of Cenozoic age, are rich in phosphatic nodules, which have been derived from organic matter. The guano deposits of the low arid islands in the West Indies illustrate another mode of accumulation of organic material useful as a fertilizer.

The assorting of surface débris by streams and currents has led to the formation of extensive deposits of clay which occur widely throughout the portions of North America where the surface is composed of stratified rock, which is extensively used in the manufacture of earthenware, bricks, tiles, terra-cotta, Portland cement, etc.

When rocks containing gold in nuggets, grains, scales, etc., are disintegrated, and the resulting débris removed by streams, mechanical separation of the heavier from the lighter material takes place and all but the very finest of the gold is concentrated on the stream beds. In this manner the rich placers of the Pacific mountain region from California to Alaska have originated.

The general nature of the ore bodies formed through the action of chemical agencies in sedimentary rocks, by solution and redeposition, is illustrated by the lead and zinc ores of Wisconsin, Missouri, the silver-bearing lodes of the Pacific mountains, etc. In the case of the lead and zinc deposits the ores occupy the interspaces between broken sedimentary beds or line caverns. Under the best explanation of the origin of these deposits that has been offered, although certain modifications of the general hypothesis have been suggested which it is not necessary to consider at length at this time, the lead and zinc are considered to have been at one time widely distributed in the adjacent sedimentary rocks, mainly limestone, and to have been taken in solution by percolating waters and carried to cavities where they were precipitated, together with various other mineral substances, such as calcium carbonate or calcite, barium sulphate or barite, carbonate of calcium and magnesium or dolomite, etc. The minerals containing lead are principally galenite or lead sulphate, cerussite or lead carbonate; while the zinc is contained in the minerals, sphalerite or zinc sulphide, calamine or zinc silicate, smithsonite or zinc carbonate, etc. These minerals, including both those containing lead and zinc, and those intimately associated with them which are at present of no commercial value, are such as are known to crystallize from solution without the aid of high temperatures. In the Missouri lead and zinc districts the ore deposits occur near the surface, the depth of the present working seldom exceeding 150 or 200 feet, and, as nearly as can be judged, have been formed by the downward transfer of mineral matter through the process of solution and recrystallization, as the surface of the land has been lowered by chemical and mechanical denudation.

Many of the rich silver-mines of the Pacific mountains occur in fissures and cavities in sedimentary rocks, mainly limestone. Instances of this nature are furnished by certain mines in northeastern Mexico, where the ore is found in cavities in Cretaceous limestone; at Leadville and Aspen, Colorado; Big and Little Cottonwood cañons, and the Horn silver-mine, Utah, where the principal country rock is Carboniferous limestone; the Eureka district, Nevada, where the ore occurs in cavities in Cambrian limestone. In the case of several of these mines, igneous rock is near at hand, and the ores are believed to owe their concentration largely to the action of heated waters.

In other regions deep fissures, occupied in part by dikes of igneous rock, have permitted of the ascent of water charged with mineral matter from far below the surface; such waters are heated, in part by the general heat of the earth's interior, or, if in association with dikes, by the heat of the once molten intruded rock. The ascending hot water is an active solvent, and as it rises becomes cooled, and for this and other reasons precipitates many mineral substances. Veins are thus formed, which are many times banded—that is, result from the filling of fissures by the successive deposition of minerals of various kinds on their walls, each different layer of minerals indicating a change in conditions. Fissures filled in this manner from below, as denudation progresses, become exposed at the surface and reconcentration through the influence of disintegration and decay, and of solution and redeposition by descending water takes place. Ore bodies of this character carrying gold, silver, mercury, etc., are of wide occurrence, especially in the Pacific mountains, but the process of concentration is independent of the nature of the country rock. Segregated and fissure veins occur in either igneous, sedimentary, or metamorphic terranes, but are more commonly of economic importance in the metamorphic rocks than elsewhere, and will be referred to again in that connection.

Economic Importance of the Metamorphic Terranes.—The great laboratory in which rocks undergo important changes in their physical condition and in mineralogical and chemical composition, is what has been termed on a previous page the zone of metamorphism. The depth of the upper limit of this zone is variable, dependent in part on the nature of the rocks and on movements within them, as is the case of mountain building. In fact, there is probably no well-defined limit to the zone either above or below, as in the former direction metamorphism merges by gradations into alteration produced by the descent of surface water, and in the latter direction as heat increases passes again, as we imagine, by insensible and irregular gradations into a region where the rocks are so highly heated that diffusion rather than concentration results. Whether the rocks below the zone of metamorphism are fused or not depends on pressure. They are probably solid, but in a potentially plastic condition, and become fused and may be forced upward through fissures in the condition of igneous magmas when pressure is relieved. The zone of metamorphism lies between a superior zone where alteration by descending water is dominant, and a lower region where alteration due mainly to heat is in control. In the zone of metamorphism the influence of heated percolating waters, combined with movements in the rocks, are the principal factors which lead to the concentration of mineral substances.

Under the influence of percolating, heated waters, new minerals are formed in sedimentary or igneous rocks, and rocks once metamorphosed may undergo additional changes. Mineral matter previously widely disseminated through rocks is, under the action of percolating, heated water, brought together and the regeneration and crystallization of a large variety of ores and minerals result. The birthplace of a large variety of ores and minerals is in the zone of metamorphism. It is in metamorphic rocks that the geologist looks for gems, the precious metals, crystalline marble, magnetic iron, etc.

For the most part, however, the native metals and ores of the precious and many of the common metals are too widely disseminated in the metamorphic rocks to be of commercial importance, and a still further concentration, principally in fissures and other cavities, is necessary before they can be of value to man. This secondary concentration is much the same as in the case of the deposition of lead and zinc ores in cavities in sedimentary rocks, and results largely from the solution and redeposition, sometimes by replacement, of mineral matter by heated waters.

Certain ores and rocks contained in metamorphic terranes owe their concentration to previously acting processes of concentration, but have undergone chemical changes in place. Illustrations of this class of ores, etc., are furnished by the magnetite and hematite contained in the metamorphic rocks on the eastern border of the Appalachians, in New England, eastern Canada, and the Lake Superior region. These ore bodies, frequently of great size, in some instances furnish evidence of having been originally lenticular masses of bog-iron ore, or ferric carbonate, associated with sedimentary beds, and originally concentrated, as already mentioned, at the surface through the action of water charged with carbon dioxide, but principally on account of the influence of heat have been changed to a higher degree of oxidation and now appear as hematite, as, for example, in the iron districts of the northern portions of Michigan, Minnesota, Wisconsin, and the Ozark Hills, or still further altered as in the richest of all iron ores, magnetite, so abundant in the metamorphic rocks of the Appalachian region, about the Adirondack hills, widely and in extensive bodies in eastern Canada, about the south shore of Lake Superior, in Texas, etc.

In certain instances, as has been shown by C. R. Van Hise and others, hematite ore, like that of the Lake Superior region, has resulted from the alteration of ferrous carbonate which had replaced limestone by a chemical process of solution and double decomposition.

As bodies of iron ore in the form of the carbonate, or limonite, may occur in rocks of any age, and as rocks of any age may be metamorphosed, it follows that hematite and magnetite may be present in any formation which has been subjected to metamorphosing conditions.

Limestone when metamorphosed is changed to a crystalline marble, frequently white in colour owing to the dissipation of its previously contained organic matter. The white marbles so extensively utilized in Georgia, Vermont, etc., are of this nature. Other similar metamorphosed layers occur in several of the ranges of the Pacific mountains from Mexico to Alaska.

The influence of metamorphism on deposits of coal when the heat has been of moderate intensity serves to drive off a large part of the volatile matter present and converts the coal into a substance resembling coke, as has happened adjacent to dikes or intruded sheets of igneous rock in the Richmond coal-field, Virginia, in New Mexico, Washington, etc. When the heat is somewhat more intense, the coal is changed to what is termed graphitic anthracite, as in the Rhode Island coal-fields, and when still greater or long-continued, results in the production of graphite, as in the Algonkian rocks about the Adirondack hills and over a wide region in eastern Canada.

An important result of metamorphism is the production of new minerals in the rocks acted on. Many of the metamorphic terranes consist essentially of quartz, feldspar, and mica, which have been formed by the rearrangement of the mineral matter contained in the rocks during their previous state. Besides these constituent minerals there are frequently others present, such as the garnets, tourmaline, emerald, sapphire, corundum, etc., which are of economic importance. In a large number of instances the minerals of metamorphic rocks are contained in veins of one class or another, in part resulting from segregation in the rocks themselves while yet in a heated condition, and in part deposited in fissures or other openings as a result of secondary concentration through the action of heated waters. The principal difference between the minerals concentrated in the metamorphic rocks and those deposited in cavities in unaltered sedimentary beds seems to be that in the former instance the percolating water which carried the material in solution had a higher temperature than in the latter case.

Among the numerous mineral substances of value in the arts, occurring in the metamorphic terranes of North America, other than building stones and the previously concentrated deposits, such as iron ore, graphite, etc., mention can only be made at present of the following:

Mica, which is used in thin sheets for the windows of stoves and furnaces, and when ground and mingled with other substances furnishes a good insulating material for electric wires, fireproofing, and also used as a lubricant, etc., occurs in large quantities in the metamorphic rocks of New Hampshire and Ottawa, and less abundantly in North Carolina, South Dakota, Wyoming, Idaho, etc. It is widely distributed, but to find transparent colourless sheets of large size is difficult.

Talc and soapstone, consisting of the hydrated silicate of magnesia, and useful for hearths, mantels, fire-brick, linings for stoves, laundry-, bath-, and acid-tubs, etc., and when ground, employed as an adulterant of soap, paper, rubber, and as a lubricant, etc., occurs widely in the metamorphic terranes on the eastern side of the Appalachians, in Canada, and at numerous localities in the Pacific mountains. The chief centres of production at present are in Pennsylvania, New Jersey, New Hampshire, and Vermont.

Asbestos, valuable on account of its fibrous structure and non-conductivity of heat, which make it an excellent insulator, and largely used in the manufacture of fireproof paper, cloth, etc., occurs in connection with serpentine, in metamorphic terranes, and is extensively mined in the Thetford district, Quebec.

Corundum, consisting of aluminum oxide, and having essentially the same composition as the sapphire and ruby, and a less pure variety of similar composition termed emery, is largely used as an abrasive in polishing metal, sharpening tools, etc., and also as "sand-paper" in working wood, occurs in commercial quantities, largely in crystalline limestone, at Chester, Mass., in Georgia, North Carolina, and several other localities. Although corundum is next to the diamond in hardness, and therefore highly favourable, when reduced to a powder, for polishing various substances, the demand for it has in recent years been diminished owing to the manufacture of an equally if not superior material termed commercially carborundum.

Among the crystals used as gems, which occur in the metamorphic rocks of North America but thus far in minor quantities, and as a rule of inferior quality, may be enumerated sapphires, rubies, tourmalines, garnets, quartz, etc.

Apatite, a mineral rich in phosphoric acid, and largely used in the manufacture of fertilizers, occurs associated with limestone in the metamorphic rocks of Quebec and Ontario in the form of veins, beds, and irregular pockets, and a few years since was extensively mined, but now, owing to foreign competition, is held in reserve.

By far the most valuable of the minerals and native metals that occur in the metamorphosed terranes is gold. Although this metal has been found in paying quantities in association with nearly every kind of country rocks and in terranes of all ages, the place of its original concentration from a previously widely disseminated condition is to a great extent in the zone of metamorphism. It occurs principally as native gold, although usually alloyed with silver, but is frequently contained in iron pyrites. In the crystalline rocks, such as gneiss, schist, slates, granite, etc., it occurs in flakes and grains, but so far as its occurrence in commercial quantities is concerned its deposition has for the most part been secondary, and the metal, usually in association with quartz, is found in veins, lodes, contact deposits, etc., and owes its concentration to chemical agencies not well understood, acting in connection with percolating water. That this general statement is correct is clearly shown by the fact that gold occurs in crystals, flakes, grains, etc., most frequently in quartz and iron pyrites, which, as can be shown in a number of ways, have crystallized from solution. The gold and its commonly associated mineral in countless instances occupy fissures and must have been carried to such localities after the surrounding rock had been fractured. So intimate is the association of gold with metamorphic rocks that this is one of the main guides in searching for it, although, as already stated, it is frequently present in other rocks as well. With the disintegration of the metamorphic terranes the gold is set free, and may be still further concentrated by streams so as to form the well-known placers.

A very large proportion of both the quartz and placer mining of North America is in regions occupied by metamorphic rock. This is true of all gold-mines, previously quite largely exploited, of the Atlantic mountain region from Georgia to eastern Canada. The mines of California are also largely in schistose rocks, as are also those to the northward, throughout the Pacific mountains, to British Columbia and Alaska, including the recently established mining district at Cape Nome.

With placer gold, and probably derived largely, if not entirely, from metamorphic rocks, there are frequently found grains of platinum. The annual production of this metal in the United States and Canada has a value of about $5,000.

The study of the distribution of native metals and ores in the metamorphic rocks of North America indicates that in general the older rocks, as the Archean, for example, are less rich than the younger terranes, such as the schist, etc., of the Sierra Nevada and Cascade Mountains. This seems to indicate that the older rocks were once deeply buried and their more soluble substances removed by ascending waters, and in part redeposited in higher terranes. Erosion has since carried off the rocks which were mineral-charged and laid bare the depleted terranes beneath. This hypothetical explanation of the general poverty of the Archean rocks is coupled with another consideration, namely, that the younger metamorphic terranes, where they have been elevated, as in the Pacific mountains, are more broken than the Archean rocks, and afford more cavities in which minerals may be deposited. Whether this is a complete explanation or not remains to be demonstrated, but observation shows that the Archean terranes—all of which as yet discovered are composed of either metamorphosed or igneous rocks—are, in comparison with younger metamorphosed rocks, relatively poor in minerals and ores of commercial importance.

Among the economic products of the rocks are included mineral waters. The direct commercial value of such waters, not including their use for baths, etc., in the United States, is about $7,000,000 annually. The demand for these waters depends largely on the mineral substances they hold in solution, and which in many instances is in process of transference from one locality to another. Much might be written in this connection in illustration of the fact that the processes by which minerals, ores, etc., have been concentrated are still in progress.

An extensive literature is available concerning the geology, minerals, ores, etc., of North America, but only a few of the more important publications can here be referred to. The numerous publications of the United States Geological Survey, the Geological Survey of Canada, and the Geological Survey of Mexico contain vast amounts of valuable information. Several of the States of the United States have independent surveys and have published numerous reports. Of journals containing articles of American geology, the more important are: The Journal of Geology, published at the University of Chicago; The American Geologist, published at Minneapolis, Minn.; The American Journal of Science, published at New Haven, Conn. The publications of a large number of learned societies in Canada and the United States should also be consulted.

The most useful bibliographies of North American geology are:

• Darton, N. H. Catalogue and Index of Contributions to North American Geology, 1732-1891. Published as Bulletin No. 127 of the United States Geological Survey, Washington, D. C., 1896.
• Dowling, D. B. General Index to the Reports of Progress [of the Geological Survey of Canada], 1863-1884. Published by the Canadian Geological Survey, Ottawa, Canada, 1900.
• Warman, P. C. Catalogue and Index of the Publications of the United States Geological Survey, 1880 to 1901. Published as Bulletin No. 177 of the United States Geological Survey, Washington, D. C., 1901.
• Weeks, F. B. Bibliography of North American Geology, Paleontology, Petrology, and Mineralogy for the Years 1892-1900, Inclusive. United States Geological Survey, Bulletins No. 188 and 189, Washington, D. C., 1902.

Of the numerous general treatises on the geology, the following will be found especially helpful to the student:

• Dana, J. D. Manual of Geology. Fourth edition. American Book Company, New York, 1895.
• Kemp, J. F. The Ore Deposits of the United States and Canada. Scientific Publishing Company, New York, 1900.
• Le Conte, J. Elements of Geology. Fifth edition, revised and partly rewritten by Prof. H. L. Fairchild. D. Appleton and Company, New York, 1903.
• Merrill, G. P. A Treatise on Rocks, Rock-Weathering, and Soils. The Macmillan Company, New York, 1897.
• Shaler, N. S. Outlines of the Earth's History. D. Appleton and Company, New York, 1898.

CHAPTER VII

In the same manner as the exploration of the New World led to the discovery of many species, genera, etc., of plants and animals, it also added two types of man to those previously known to Europeans. The propriety of separating the American aborigines into two groups of tribes is based on the contrasts the members of these divisions present not only in colour and other physiological characteristics, but on well-marked differences in language, customs, arts, etc. On this basis two varieties of the human species have been recognised, namely, the Eskimo and the Indian.

The term Eskimo, formerly spelled Esquimau, is of obscure origin, but is thought to have been adopted by Europeans from the Indians of Labrador, who thus designated a northern people living on the coast, and is said to mean "raw-flesh eaters." The word in use among the Eskimos to designate themselves is Innuit, meaning people, or the people, in the sense that in their own estimation they are of more importance than all other peoples.

The term Indian, as is well known, arose from an error of the early Spanish voyagers, who, on arriving in America, believed they had reached India, and hence termed the natives of the new land Indians. This mistake has led to many attempts to substitute some other word by which to designate the people referred to, but thus far none of the terms proposed has been generally accepted. In the present book the word Indian is used to designate the aborigines of the New World, exclusive of the Eskimos.

The geographical distribution of the Eskimos and Indians is sharply defined even at the present day, and is indicated on the map forming Plate VI.

Origin of the Aborigines.—The generally accepted conclusion in reference to the origin of the American aborigines seems to be that man reached this continent while the peoples of the Old World were yet in a primitive condition, and at a time when the highest stage of culture was expressed by the knife and spear-point of chipped stone, and developed independently in accord with the natural conditions with which he was surrounded. More than this, once planted, the original stock received but slight if any accessions by subsequent immigration. This last statement is not in strict accord with the conclusions reached by certain ethnologists, who claim that the use of masks, the art of carving on wood, stone, ivory, etc., the practise of tattooing, the preservation of human heads, and other customs practised by the Indians of the Pacific coast of the two Americas—and in North America, extending eastward along lines of easiest communication—suggest an influence coming from Polynesia at a time when the peoples dwelling on the west borders of the Pacific had made a well-marked advance in culture. Some influences on the aborigines of America coming both from Polynesia and eastern Asia must seemingly be admitted, the importations having been by means of storm- and current-swept boats and junks, but the evidence does not point to trade relations. The most that can be claimed seems to be slight modifications of the arts and customs of the American aborigines, but not enough to make what may be termed an indelible impression upon them.

The low state of culture of the original stock from which the American aborigines were derived, implied in their distinct subsequent development in language, arts, etc., indicates that man appeared in America previous to the invention of boats capable of crossing broad oceans. The necessary inference from this—if the hypothesis of one place of origin for the human race is accepted—is that migration to America was by land, or at most across narrow straits. The geography of the continents must have been markedly different from what it is at present to admit of this, providing the proof that access was not gained where Asia and America make a near approach to each other at Bering Strait is conclusive, and at present that evidence seems unquestionable.

The present state of opinion in reference to the origin of the American aborigines is thus expressed by one well qualified to speak with authority. At the close of a review of several lines of evidence J. W. Powell says:

"Thus we are forced to conclude that the occupancy of America by mankind was anterior to the development of arts, industries, institutions, languages, and opinions; that the primordial occupancy of the continent antedates present geographical conditions, and points to a remote time which can be discovered only on geological and biological investigation."

Antiquity of the Aborigines.—The conclusions to be drawn from the studies of ethnologists in reference to the length of time man has made his home in America are qualitative, not quantitative. The time is certainly long, probably embracing tens of centuries; but how long no one can state in years. This claim for a great although indefinite antiquity is based on several lines of evidence, some few of which the reader may find it profitable to briefly consider.

A comparison of physiological characteristics shows that the American aborigines have well-marked differences from all other varieties of the human race. This conclusion is not based on any one special feature, although colour and character of the hair are the most conspicuous, but on the resultant, so to speak, of many attributes. It is, in a measure, a comparison of ideal type-examples of each variety. While each characteristic that may be chosen has individual and tribal variations, and but few of them are perhaps conspicuously different from those pertaining to the peoples of the Old World, yet taken together they clearly differentiate the American aborigines from all other varieties of the human species.

Applying the same principles to man that are used in the study of the geographical distribution of the lower animals, the only legitimate conclusion the naturalist can deduce from the evidence just referred to is that the branch of the human family indigenous to North America has been isolated for a sufficient length of time to develop into a new variety. The American aborigines are different from all other varieties of the human species because each more or less isolated community or group of communities the world over has varied in its own way in accord with climatic and other conditions, and the connecting links have been lost. The differences that have arisen in this manner are so great that the nature of the parent stock is no longer determinable from its living representatives. This process of development among the lower animals is understood to involve a great length of time; and the inference is that man's development is no exception to the rule.

The evidence favouring a great antiquity for the American aborigines is strengthened by the fact that when first known to Europeans both North and South America were inhabited by tribes having more or less well-defined territorial limits. If this population spread from one or even from several centres it is evident that a great length of time would be required for it to reach all parts of the New World and to become adjusted to a wide range in climatic and other conditions, as is known to be the case.

Students of languages have shown that the most enduring characteristics of man are to be found in his speech. The fundamental principles of a language outlive not only political and social changes, but even physiological distinctions, and are inherited from a primitive stock by all its branches. We might reasonably expect, therefore, that a study of the languages spoken in America in pre-Columbian days would be a sure index as to the primitive stock from which the various tribes came, and show to which of the many other branches of the linguistic tree they are most closely related. Turning with this question to those who have made a critical study of the languages of the American aborigines, and no one is better qualified to bear testimony in this connection than J. W. Powell, the honoured director of the American Bureau of Ethnology, we find a definite answer. He says:

"The North American Indian tribes, instead of speaking related dialects, originating in a single parent language, in reality speak many languages, belonging to distinct families, which have no apparent unity of origin."

To the north of Mexico (Plate VI) the aborigines are divided into 58 linguistic families. In a large portion of these languages there are tribal dialects not understood by members of other tribes of the same family. Thus the Algonquin linguistic family contains some 30 or 40 distinct languages. In the Athapascan the diversity is nearly as great. The smaller families present similar conditions in proportionate degree, although there are stocks which speak but one language. Four of the linguistic families referred to extend into Mexico, but to the south of the territory occupied by them other languages and dialects are spoken. Ethnologists who have studied the tribes of Mexico report 19 linguistic stocks, containing 108 distinct languages, among which there are upward of 60 dialects. In Central America a similar diversity in the native tongues exists. Reclus, in his great work The Earth and its Inhabitants, states that in the New World 450 native languages are spoken—a number greater than that of all the languages in use in the rest of the earth. Not only are the American linguistic stocks different from each other, and fail to furnish evidence of having been derived from a single parent tongue, but, as philologists assure us, no one of them is analogous to any language spoken in other lands.

As is well known, a language is not created de novo, but by a slow process of development. Since the first acquirement of articulate speech by man a succession of languages has appeared owing to the growth, differentiation, etc., of pre-existing forms of speech. It is a warrantable inference, therefore, that the marvellous diversity in speech present in America could only have arisen by a process of evolution involving a very long period of time.

As the American languages have no affinity with the Teutonic or Semitic stocks, it is evident that the source or sources from which they came far antedate the birth of the oldest people of which history takes cognizance. Man must therefore have set foot on American soil before the sprouting of the linguistic twig which, after millenniums, produced the cuneiform inscriptions of ancient Persia and Assyria.

The diversity of arts, customs, myths, religions, etc., among the American aborigines, and their difference in nearly all instances from the analogous attributes of the peoples of other lands, also point to a long period of isolated development in much the same manner as has been referred to in the case of a comparative study of their languages. The skin boats used by the Eskimos are widely different from the birch-bark canoes of the Algonquins, and these again differ conspicuously from the dug-out canoes of southeastern Alaska and British Columbia; still other varieties of boats are peculiar to the more southern Indian tribes, and all alike differ from the boats used in other lands. Like individuality pertains also to the houses of the American aborigines, their clothing, arms, utensils, basket-work, picture-writings, etc. One is forced to recognise in each of these arts or industries not only development in many diverging lines among the various tribes, but the birth of ideas analogous to those which arose in other lands, and their independent growth under special conditions. All of this, and much more in the same general direction that might be discussed did space permit, points to a great antiquity for the indigenous American peoples.

Among the nations of the Old World certain plants have been under domestication for so long a time, and have varied so greatly, that the wild species from which they came are no longer known. This is true of nearly all our common fruits and vegetables and many of our flowers that were derived from the Old World. At the time of the Spanish conquest the aborigines of America were cultivating tobacco, potatoes, beans, tomatoes, squashes, maize, cotton, etc., and in the case of most of these plants the wild species from which they were derived has not been ascertained. The argument that points to a great antiquity in the case of wheat and the peach applies equally well to tobacco and maize, and indicates that horticulture began in America in remote antiquity. At the time of Columbus, the ox, sheep, goat, pigeons, fowls, cat, etc., long domesticated in the Old, were absent in the New World, and the llama, turkey, etc., indigenous in America, were unknown in Europe. These striking differences, among which there is not even a single exception, amount to positive evidence that contact between the peoples of the Old and the New World did not occur after the inhabitants of the former emerged from savagery, or, what is the same thing, never existed in the sense that trade relations were entered into. This same line of argument seemingly casts grave doubts on the deductions already referred to concerning the importation into America from Polynesia of the practise of tattooing, the wearing of masks, the use of labrets, etc.; and indicates also that but slight changes were produced in the American aborigines owing to the wrecking of Asiatic junks on the northwest coast.

Another factor bearing on the antiquity of the indigenous Americans is the stage of development reached in spite of their long and nearly complete isolation. Stimuli from without, and particularly contact with more advanced peoples, having been lacking or of small importance, incentive to bodily and mental activity arose mainly from the desire for food, clothing, and shelter, and from intertribal rivalry, jealousy, and war. This process of indigenous development was certainly slow. With man, as with the lower animals, the rate of advance and of specialization increases as higher and higher grades of development are reached. For the American aborigines to have attained the higher stages of barbarism at the time of the arrival of civilized Europeans, solely by self-growth and self-education, is perhaps even a stronger argument for their antiquity than their differentiation in culture, languages, etc.

These several lines of evidence point to the coming of man to America as an event of the far distant past—a time so remote, in fact, that it pertains to geology rather than to ethnology.

Turning to the geological records, we find no authentic and well-attested evidence of the presence of man in America either previous or during the Glacial period. From time to time so-called "finds" of stone implements in gravel and other deposits more or less definitely determined to be of Glacial age have been made, but in all of these instances convincing proof as to the age of the deposits, or of the relation of the implements in question, to them, has not been presented. Certain discoveries of the bones of men and of articles of human manufacture found in California have been claimed to be of Tertiary age—that is, much older than the Glacial epoch—but more critical studies, especially by W. H. Holmes, have shown that they are decidedly modern and pertain to the Indians still living in the region where they were found. In brief, all the geological evidence thus far gathered bearing on the antiquity of man in America points to the conclusion that he came after the Glacial epoch. Judgment in this respect, however, should be held in abeyance, as the search for evidence is as yet incomplete.

As the problem now stands, the origin of the American aborigines is not only unknown, but no generally accepted or fairly promising hypothesis as to the land from which they came, the route followed, or the date of their arrival is to be found among the large number suggested. A continuation of the critical, ethnological, and geological studies now in progress, it is hoped, will do much to clear away this mystery, but at present only small progress can be truthfully reported.

Culture of the Aborigines.—In the classification of peoples in terms of culture three main divisions are commonly recognised, namely, savagery, barbarism, and civilization; but the boundaries between these divisions are not sharply defined and a wide range of intermediate gradations is easily discernible.

By savagery is understood the lowest grade of culture and of ethics, in which social customs are lax or wanting and tribal organization not attempted. In the condition of savagery people are without permanent homes, do not attempt agriculture or even horticulture, have no domesticated animals except perhaps the dog, and subsist on fish and game, including molluscs, small mammals, and reptiles, and such seeds, fruits, nuts, etc., as wild plants supply. The art of kindling fire is probably known to all existing savages, but much of their food is eaten uncooked.

In the state of barbarism tribal organization may exist; some form of religion is usually recognised; definite marriage relations are entered into, although polygamy is commonly practised; permanent houses, perhaps for winter use only, are built; clothes are made from woven cloth as well as from skins; the plaiting of baskets and the art of making coarse pottery, frequently highly decorated, are understood; essentially all utensils, arms, etc., are of stone, wood, bone, or ivory, the metals other than those occurring in a native state being unknown; and writing is unknown, although pictographs may be employed.

Civilization implies a well-marked development in ethics, laws, social organization, institutions, arts, writing, etc.

Under this scheme of classification various divisions of the aborigines of North America at the time of the coming of Columbus occupied each of the planes of development designated; but those frequently classed as civilized had not arrived at an advanced stage of culture, and can perhaps with greater propriety be designated as semicivilized, or, better still, be referred to the highest stage of barbarism.

Some of the native tribes, as those of southern California and certain of the peoples of Mexico and Central America, were in a state of savagery, and, in fact, have not advanced beyond that state at the present day. A large majority of the aborigines, as, for example, the Algonquins, Shoshoneans, etc., or, in general, all of the Indians to the northward of Arizona and New Mexico, together with certain of the tribes to the south of that boundary, had definite tribal organization, permanent homes at least for winter use, in part practised horticulture, and for these and other reasons are to be classed as in the barbarous stage of development. The Aztecs, Mayas, etc., of Mexico and Central America had well-established governments, built permanent and frequently large and elaborately decorated houses, some of which were of hewn stone, practised horticulture with the aid of irrigation, had developed a system of picture-writing, and were skilled in working native metals. These and other advances towards civilization were great and promising, but the use of iron was unknown, and their practice of human sacrifice and the absence of phonetic writing denies them a place among truly civilized peoples.

Another scheme for the classification of peoples in terms of the highest grade of implements used by them is current under which they are placed in certain ages on the assumption that man in all regions has passed through an orderly sequence in his development, and that the successive changes are expressed by the nature of the material used in the manufacture of implements. Under this plan of classification we have an age of stone, an age of bronze, and an age of iron. The stone age is commonly divided into two parts: an earlier or paleolithic, during which the highest type of implement used is fashioned of stone by chipping; and a later, or neolithic, when implements of stone are shaped by grinding and polishing. Following the stone age came one of bronze, when a mixture of copper and tin was used for implements; and later the age of iron, beginning when the art of reducing metals from their ores was discovered. In this scheme a copper age is sometimes included, with doubtful propriety, however, if, as in America, the metal referred to is obtained in its native condition.

Under the somewhat indefinite scheme of classification just referred to the North American aborigines, inclusive of the Aztecs, etc., previous to the coming of European civilization were in the stone age of development, although bronze was in use among the Incas of Peru, and to some extent had found its way northward as far as Mexico. Certain of the tribes still used implements of chipped stone, but in the great majority of instances implements of polished stone were the highest type known. Native copper was widely used for axes, knives, ornaments, etc., but iron, except such as occurs in meteors, was unknown.

The difficulty met with in selecting any one article or any one material used by primitive peoples as a basis for their classification is illustrated by the facts just cited, as it places the lowest savage of America in the same group as the Aztec and the Maya. Obviously, in the classification of peoples as with the lower animals all characteristics should be included.