Strata Sentence Examples

Marsh, who, after 1870, discovered a great number of bird remains in the Cretaceous strata of North America.

In the lower strata were discovered the remnants of Cyclopean or prehistoric architecture already mentioned.

Its congeners even then lived in England, as is proved by the fact that their relics have been found in the Stonesfield oolitic rocks, the deposition of which is separated from that which gave rise to the Paris Tertiary strata by an abyss of past time which we cannot venture to express even in thousands of years.

The mountains are composed in great part of Paleozoic strata, often modified by vulcanism and greatly denuded and sculptured by wind and water erosion.

The successive " Minoan " strata, which go well back into the fourth millennium B.C., reach down to a depth of about 17 ft.

There are four formations of Cretaceous strata in Mississippi, defined by lines having the same general direction as the one just described.

Seven formations (or groups) of the Tertiary strata have been distinguished in Mississippi.

It is, indeed, as if the high land of central Asia had been pushed southward against and over the unyielding mass formed by the old rocks of the Indian peninsula, and in the process the edges of the over-riding strata had been crumpled and folded.

There were, moreover, other and broader oscillations which raised or lowered extensive areas withbut much crumpling of the strata, and to these are due some of the most important breaks in the geological series.

A region where volcanic activity has led to the embedding of dykes or bosses of hard rock amongst softer strata produces a plain broken by abrupt and isolated eminences.'

Over the greater part of the Cambrian country the strata are still nearly as flat as when they were first laid down, and the deposits, even of the Cambrian period, are as soft as those of the Mesozoic and Tertiary formations in England.

Such lakes (in common with all the plateau hamuns of south-west Baluchistan and Persia) change their form and extent from season to season, and many of them are impregnated with saline deposits from the underlying strata.

In the Carboniferous strata (Coal measures) remains of Hexapods become numerous and quite indisputable.

In the south-east of Bosnia the predominant formations are Triassic and Palaeozoic strata with red sandstone and quartzite.

The steep icewalls at the margin of the inland ice show, especially where the motion of the ice is slow, a distinct striation, which indicates the strata of annual precipitation with the intervening thin seams of dust (Nordenskidld's kryokonite).

Beds of this age, consisting of sandstones and coal, are found on the northern coast of Disco Island and the southern side of the Noursoak Peninsula, the beds in the former locality, " the Kome strata " of Nordenskiold, being the oldest.

Still, the presence of dicotyledonous leaves, such as Magnolia alternans, in the Atanakerdluk strata, proves their close alliance with the Dakota series of the United States.

Undue stress is often laid on the fact that Lingula has come down to us apparently unchanged since Cambrian times, whilst Crania, and forms very closely resembling Discina and Rhynchonella, are found from the Ordovician strata onwards.

C. White, of the U.S. Geological Survey, who found strata of fairly good coal at depths of 100 to 200 ft.

That it results from the weight of the overlying strata.

Although petroleum wells in Russia have not the depth of many of those in the United States, the disturbed character of the strata, with consequent liability to caving, and the occurrence of hard concretions, render drilling a lengthy and expensive Drilling in operation.

The highest strata (Volcanic group) form the rugged elevated spurs of the Drakensburg mountains which extend along the eastern territorial boundary.

The Trilobites are known only as fossils, mostly Silurian and prae-Silurian; a few are found in Carboniferous and Permian strata.

The genus Agnostus, which belongs to the last category, occurs abundantly in Cambrian strata and is one of the earliest forms A known.

These chapadas and elevations, which are usually described as mountain ranges, are capped by horizontal strata of sandstone and show the original surface, which has been worn away by the rivers, leaving here and there broad flat-topped ridges between river basins and narrower ranges of hills between river courses.

A considerable part of it has been excavated by these rivers to a level which gives their valleys the elevation and character of lowlands, though isolated hills and ranges with the characteristic overlying horizontal sandstone strata of the ancient plateau show that it was once a highland region.

Devonian beds also lie upon the older rocks in the Matto Grosso and other provinces in the interior of Brazil, where they generally form plateaux of nearly horizontal strata.

Pre-Darwinian zoologists had been aware of the class of facts thus interpreted by Fritz Muller, but the authoritative view on the subject had been that there is a parallelism between (a) the series of forms which occur in individual development, (b) the series of existing forms from lower to higher, and (c) the series of forms which succeed 'one another in the strata of the earth's crust, whilst an explanation of this parallelism was either not attempted, or was illusively offered in the shape of a doctrine of harmony of plan in creation.

In the latter range a few Ordovician fossils have been found, but in general the oldest strata which have yielded organic remains belong to the Cretaceous system.

The contorted strata of slate and greywacke rock must have been formed at a period vastly anterior to that in which the lake of the upper valley managed to force an outlet through the enclosing barriers.

All the strata intersected by the Rhine between Bingen and Bonn contain fossils of the same classes.

The shape of the hills and ridges is necessarily influenced by the inclination of the strata, by the relative hardness of different rock-beds, and by the presence of folds and fissures and other lines of weakness.

A quartz vein or bed of hard rock may show itself as a sharp ridge or as a well-defined bench; a stratum of soft rock or the line of a great fissure, or the weakening of the strata by an anticlinal fold, may produce a ravine or a deep valley.

A tunnel differs from a drift in that it is driven across the strata to intersect the deposit.

Drifts and inclined shafts following the deposit may prove difficult of maintenance when the workings become large and settlement of the overlying strata begins.

Rock-filling yields and becomes consolidated under heavy pressure, and therefore does not furnish a rigid support of the overlying strata, but rather a cushion to control and equalize the subsidence.

Above, the ground has been completely worked out from the surface, and the space formerly occupied by ore is now filled with the debris of the overlying strata which has caved in above the block of ore now being worked.

The special difficulties which attend deep mining, in addition to the problems of hoisting ore and raising water from great depths, are the increase of temperature of the rocks and the pressure of the overlying strata.

Intrusions of a serpentine-like rock break through the Miocene strata north of Bhamo, and similar intrusions occur in the western ranges.

At a time when the Cartesian system of vortices universally prevailed, he found it necessary to investigate that hypothesis, and in the course of his investigations he showed that the velocity of any stratum of the vortex is an arithmetical mean between the velocities of the strata which enclose it; and from this it evidently follows that the velocity of a filament of water moving in a pipe is an arithmetical mean between the velocities of the filaments which surround it.

He considered the horizontal strata of this hyperboloid as always in motion, while the remainder of the water was in a state of rest, and imagined that there was a kind of cataract in the middle of the fluid.

He supposed that the surface of the fluid, contained in a vessel which is emptying itself by an orifice, remains always horizontal; and, if the fluid mass is conceived to be divided into an infinite number of horizontal strata of the same bulk, that these strata remain contiguous to each other, and that all their points descend vertically, with velocities inversely proportional to their breadth, or to the horizontal sections of the reservoir.

The geological formation of the soil belongs to the Quaternary and Pliocene period in its upper strata, and to the Eocene and Cretaceous in the lower.

The oldest strata, consisting of gypsiferous marls, are referred to the Muschelkalk and show an alternation of lagoon with marine conditions.

The Central Cordillera consists mainly of crystalline and volcanic rocks, on each side of which are aqueous, in great part Jurassic, strata thrown up almost vertically.

The whole range is highly auriferous, and the thickness of the strata is not less than 10,000 ft.

Before the object can pierce the dense lower strata of air its material is usually exhausted, but on rare occasions it withstands the fiery ordeal, and fragments of the original mass fall upon the earth.

The Cyclostomata are numerous in Palaeozoic rocks, but attained a specially predominant position in the Cretaceous strata, where they are represented by a prpfusion of genera and species; while they still survive in considerable numbers at the present day.

On the other hand, limestone and sandstone, especially of the Mesozoic strata, are strikingly deficient.

In the western Carpathians the inner zone consists of a foundation of Carboniferous and older rocks, which were folded and denuded before the deposition of the succeeding strata.

The hills west of the town consist of horizontal strata of sandstone covered with irregular pieces of basalt and the top of the hill on which the observatory stood was made level by taking away the basalt.

The general dip of the strata is from W.S.W.

The larger part of the water supply, however, is now derived by pumping from strata at about sea-level.

These strata are generally impregnated with salt water, and are practically impenetrable to the rain-water of less weight.

The honeycomb of rock, and capillary action, retard the lighter fresh-water from sinking to the sea; the soakage from rain has therefore to move horizontally, over the strata about sea-level, seeking outlets.

And yet in the European Stone age which followed, the age in which the great menhirs and cromlechs were erected, in which the domestication of animals began and the first corn was sown, we find in the strata no image of man or beast, big or little.

Lyell demonstrated to the satisfaction, or - perhaps it should rather be said - to the dissatisfaction, of his contemporaries that the story of the geological ages as recorded in the strata of the earth becomes intelligible only when vast stretches of time are presupposed.

Among these were the exponential calculus, and the curve called by him the linea brachistochrona, or line of swiftest descent, which he was the first to determine, pointing out at the same time the relation which this curve bears to the path described by a ray of light passing through strata of variable density.

These properties are most highly developed in the substance known as jet, which is a variety of cannel found in the lower oolitic strata of Yorkshire, and is almost entirely used for ornamental purposes, the whole quantity produced near Whitby, together with a further supply from Spain, being manufactured into articles of jewellery at that town.

Lignites, as a rule, are generally found in strata of a newer geological age, but there are many instances of perfect coals being found in such strata.

Such changes seem, however, to have been very rapidly accomplished, as pebbles of completely formed coal are commonly found in the sandstones and coarser sedimentary strata alternating with the coal seams in many coalfields.

It has been variously attributed to metamorphism, consequent upon igneous intrusion, earth movements and other kinds of geothermic action, greater or less loss of volatile constituents during the period of coaly transformation, conditioned by differences of permeability in the enclosing rocks, which is greater for sandstones than for argillaceous strata, and other causes; but none of these appears to be applicable over more than limited areas.

We might therefore expect to find coal wherever strata of estuarine origin are developed in great mass.

This is actually the case; the Carboniferous, Cretaceous and Jurassic systems (qq.v.) contain coal-bearing strata though in unequal degrees,- the first being known as the Coal Measures proper, while the others are of small economic value in Great Britain, though more productive in workable coals on the continent of Europe.

These are also called the Upper Limestone Shale, a similar group being found in places below the limestone, and called the Lower Limestone Shale, or, in the north of England, the Tuedian group. Going northward the beds of limestone diminish in thickness, with a proportional increase in the intercalated sandstones and shales, until in Scotland they are entirely subordinate to a mass of coal-bearing strata, which forms the most productive members of the Scotch coalfields.

These are not, however, always found together, the Coal Measures being often covered by strata belonging to the Trias or Upper New Red Sandstone series.

This derangement being carefully noted, another bore to the outcrop on the same principle is put down for the purpose of proving the seam C; the nature of the strata at first is found to agree with the latter part of that bored through in No.

The actual coal measure strata, consisting mainly of shales and clays, are generally impervious to water, but when strata of a permeable character are sunk through, such as the magnesian limestone of the north of England, the Permian sandstones of the central counties, or the chalk and greensand in the north of France and Westphalia, special methods are required in order to pass the water-bearing beds, and to protect the shaft and workings from the influx of water subsequently.

Of these methods one of the chief is the plan of tubbing, or lining the excavation with an impermeable casing of wood or iron, generally the latter, built up in segments forming rings, which are piled upon each other throughout the whole depth of the water-bearing strata.

The introduction of these special methods has considerably simplified the problem of sinking through water-bearing strata.

The third method of sinking through water-bearing strata is that of boring, adopted by Messrs Kind & Chaudron in Belgium and Germany.

Poetsch in 1883, and originally applied to shafts passing through quicksands above brown coal seams, has been applied with advantage in opening new pits through the secondary and tertiary strata above the coal measures in the north of France and Belgium, some of the most successful examples being those at Lens, Anzin and Vicq, in the north of France basin.

A portion of this may be got by the process known as robbing the pillars, but the coal so obtained is liable to be very much crushed from the pressure of the superincumbent strata.

In the deeper German pits, where great thicknesses of water-bearing strata have to be traversed, the first establishment expenses are so great that in order to increase output the shaft is sometimes provided with a complete double equipment of cages and engines.

The genus has a very wide distribution, extending from Europe through Asia to North America, and occurring in strata which are of Oligocene and Miocene age.

Soil, Climate, &c. - The surface soil is a curious kind of red earth, which is also found in ochre-like strata throughout the limestone.

There the gigantic cliffs, with their banded strata, have been broken into fantastic forms by the waves.

The Silurian formation which covers Esthonia, appears in the northern part of Livonia, the remainder of the province consisting of Devonian strata.

The phosphatic rocks which occur among the sedimentary strata are the principal sources of phosphates for commerce and agriculture.

The " Challenger " and other oceanographic expeditions have shown that on the bottom of the deep sea concretions of phosphate are now gathering around the dead bodies of fishes lying in the oozes; consequently the formation of the concretions may have been carried on simultaneously with the deposition of the strata in which they occur.

The phosphate beds contain Eocene fossils derived from the underlying strata and many fragments of Pleistocene vertebrata such as mastodon, elephant, stag, horse, pig, &c. The phosphate occurs as lumps varying greatly in size, scattered through a sand or clay; they often contain phosphatized Eocene fossils (Mollusca, &c.).

Bands of black nodules, highly phosphatic, are found at the top of the Bala limestone in North Wales; beds of concretions occur in the Jurassic series; and important deposits are known in the Cretaceous strata, especially in the Lower Greensand and at the base of the Gault.

The most pronounced of these upfolded strata in New York form the low Shawangunk mountains, which descend, toward the S.E., to a lowland region of folded strata of limestone, slate and other rocks in Orange and Dutchess counties.

In the Great Plains region the geological structure is very simple, consisting of nearly horizontal strata of Cretaceous rock in the middle and western portions, and of Tertiary rock on the eastern border, but in the mountain region the rocks have been folded and faulted until the structure is intricate and obscure.

Former tributaries have given place to others developed with reference to the distribution of more or less easily eroded strata, the present longitudinal valleys being determined by the out-crop of soft shales or soluble limestones, and the parallel ridges upheld by hard sandstones or schists.

In the Chaldaean signs fragments of several distinct strata of thought appear to be embedded.

Palaeontology is the study of the fossils found in the various strata of which the earth is composed.

The strata in which it was found belong to the Miocene or Upper Pliocene.

Fossil remains of extinct bears first occur in strata of the Pliocene age.

The dolerite of Fair Head sends off sheets along the bedding-planes of these carboniferous strata.

The strata which form the Balearic Isles fall naturally into two divisions.

The factor T becomes of importance in long range high angle fire, where the shot reaches the higher attenuated strata of the atmosphere; on the other hand, we must take about 800 in a calculation of shooting under water.

Carboniferous and Permian strata are possibly represented by some black and grey micaceous shales with beds of coal in the Jurjura.

Shaler, state geologist in 1873-1880, " When the rocks whence they flow were formed on the Silurian sea-floors, a good deal of the sea-water was imprisoned in the strata, between the grains of sand or mud and in the cavities of the shells that make up a large part of these rocks.

While establishing the historic divisions of the Silurian in Bohemia, Barrande also propounded his famous theory of " colonies," by which he attempted to explain the aberrant occurrence of strata containing animals of a more advanced stage among strata containing earlier and more primitive faunas; his assumption was that the second fauna had migrated from an unknown neighbouring region.

It is with respect to this number of segments that respectively constitute the pygidium and the midregion of the body that Trilobites differ most markedly from each other; and it is a singular fact that the extremes in structural organization in this particular to be met with in the Trilobita are found side by side in strata of Cambrian age.

That these animals were widely distributed in former times is proved by their occurrence at the present day in palaeozoic fossiliferous strata both of the northern hemisphere and of Australia; and despite the fact that their remains have not been found in rocks of the Mesozoic or Kainozoic epochs, it was conceived to be possible that living specimens might be dredged from the sea-floor during the exploration of the ocean depths undertaken by the "Challenger" expedition.

Both were remarkable for the great mass of early painted pottery that was found; in the temple of Apollo this had been buried in a trench; in that of Aphrodite it was scattered over the whole surface in two distinct strata.

In a south-western section the crystalline belt again assumes importance in breadth and height, and the plateau member maintains the strength that it had in the middle section, but the intermediate stratified belt again has fewer ridges, -because of the infrequence here of ridge-making strata as compared to their frequency in the middle section.

The mountain-making compression of the, 4pialaheavy series of Palaeozoic strata has here produced a chians.

The watercourses to-day are, as a rule, longitudinal, following the strike of the weaker strata in paths that they appear to have gained by spontaneous adjustment during the long Mesozoic cycle; but now and again they cross from one longitudinal valley to another by a transverse course, and there they have cut down sharp notches or water-gaps in the hard strata that elsewhere stand up in the long even-crested ridges.

The horizontal strata of the plateau present equal ease or difficulty of erosion in any direction; the streams and the submature valleys of the plateau therefore ramify in every direction, thus presenting a pattern that has been called insequent, because it follows no apparent control.

For the most part the rivers follow open valleys along belts of weak strata; but they frequently pass through sharp-cut notches in the na1row ridges of the stratified beltthe Delaware water-gap is one of the deepest of these notches; and in the harder rocks of the crystalline belt they have eroded steep-walled gorges, of which the finest is that of the Hudson, because of the greater height and breadth of the crystalline highlands there than at points where the other rivers cross it.

Many of the rivers, elsewhere well graded, have rapids as they pass from the harder rocks of the piedmont to the semi-consolidated strata of the coastal plain.

The feature referred to results from the occurrence here of a weak basal formation of clay overlaid by more resistant sandy strata; the clay belt has been stripped for a score or more of miles from its original inland overlap, and worn down in a longitudinal inner lowland, while the sandy belt retains a significant altitude of 200 or 300 ft.

The exposed strata are in large part resistant sandstones.

In certain parts of the plateau there are narrow anticlinal uplifts, an outlying effect of mountain-making compression; here a ridge rises if the exposed strata are resistant, as in Chestnut ridge of western Pennsylvania; but here a valley is excavated if the exposed strata are weak, as in Sequatchie Valley, a long narrow trough which cuts off a strip of the plateau from its greater body in Tennessee.

Again, in Kentucky and Tennessee, there is a double alternation of sandstone and limestone in the plateau-making strata; and as the skyline of the plateau bevels across these formations, there are west-facing escarpments, made ragged by mature dissection, as one passes from the topographically strong sandstone to the topographically weak limestone.

The erosion of the region must have been far advanced, perhaps practically completed, in very ancient times, for the even surface of the peneplain is overlapped by fossiliferous marine strata of early geological date (Cambrian); and this shows that a depression of the region beneath an ancient sea took place after a long existence as dry land.

The extent of the submergence and the area over which the Palaeozoic strata were deposited are unknown; for in consequence of renewed elevation without deformation, erosion in later periods has stripped off an undetermined amount of the covering strata.

It is of greater altitude (Mt Marcy 5344 ft.) and of much greater relief than the Superior Oldland; its heights decrease gradually to the north, west and south, where it is unconformably overlapped by Palaeozoic strata like those of Minnesota and Wisconsin; it is of more broken structure and form on.

The strata are the deposits of an ancient sea, which in the earlier stage of geological investigation was thought to be part of the primeval ocean, while the Laurentian highlands were taken to be the first land that rose from the primeval waters.

Inasmuch, however, as the floor on which the overlapping strata rest is, like the rest of the Laurentian and Superior Oldland, a worn-down mountain region, and as the lowest member of the sedimentary series usually contains pebbles of the oldiand rocks, the better interpretation of the relation between the two is that the visible oldiand area of to-day is but a small part of the primeval continent, the remainder of which is still buried under the Palaeozoic cover; and that the visible oldiand, far from being the first part of the continent to rise from the primeval ocean, was the last part of the primeval continent to sink under the advancing Palaeozoic seas.

When the oldland and its overlap of stratified deposits were elevated again, the overlapping strata must have had the appearance of a coastal plain; but that was long ago; the strata have since then been much eroded, and to-day possess neither the area nor the smooth form of their initial extent.

As is always the case in the broad denudation of the gently inclined strata of such plains, the weaker layers are worn down in sub-parallel belts of lower land between the oldiand and the belts of more resistant strata, which rise in uplands.

Its relief is seldom more than 200 or 300 ft., and is commonly of small measure, but its continuity and its contrast with the associated lowlands worn on the underlying and overlying weak strata suffice to sake it a feature of importance.

The cuesta would be straight from east and west if the slant of the strata were uniformly to the south; but the strata are somewhat warped, and hence the course of the cuesta is strongly convex to the north in the middle, gently convex to the south at either end.

The arrangement of the Great Lakes is thus seen to he closely synipathetic with the course of the lowlands worn on the two belts of weaker strata on either side of the Niagara cuesta; Ontario, Georgian Bay and Green Bay occupy depressions in the lowland on the inner side of the cuesta; Erie, Huron and Michigan lie in depressions in the lowland on the outer side.

In Wisconsin the inner lowland presents an interesting feature in a knob of resistant quartzites, known as Baraboo Ridge, rising from the buried oldland floor through the partly denuded cover of lower Palaeozoic strata.

The lowland is enclosed by an upland or cuesta, known as Chunnenugga Ridge, sustained by partly consolidated sandy strata; the upland, however, is not continuous, and hence should be described as a maturely dissected cuesta.

Its inner border affords admirable examples of topographical discordance where it sweeps north-westward square across the trend of the piedmont belt, the ridges and valleys, and the plateau of the Appalachians, which are all terminated by dipping gently beneath the unconformable cover of the coastal The, lain strata.

Important salt deposits occur in the coastal plain strata near the coast.

Then comes the East Texas timber belt, broad in the north-east, narrowing to a point before reaching the Rio Grande, a low and thoroughly dissected cuesta of sandy Eocene strata; and this is followed by the Coast Prairie, a very young plain, with a seaward slope of less than 2 ft.

The Great Plains.A broad stretch of country underlaid by nearly horizontal strata extends westward from the 97th meridian to the base of the Rocky Mountains, a distance of from 300 to 500 in., and northward from the Mexican, boundary far into Canada.

The strata here are Cretaceous or early Tertiary, lying nearly horizontal.

This mountain mass is of flat-arched, dome-like structure, now well dissected by radiating consequent streams, so that the weaker uppermost strata have been eroded down to the level of the plains where their upturned edges are evenly truncated, and the next following harder strata have been sufficiently eroded to disclose the core of underlying crystalline rocks in about half of the domed area.

An important geological characteristic of most of the Cordilferan region is that the Carboniferous strata, which in western Europe and the eastern United States contain many coal seams, are represented in the western United States by a marine limestone; and that the important unconformity which in Europe and the eastern United States separates the Palaeozoic and Mesozoic eras does not occur in the western United States, where the formations over a great area follow in conformable sequence from early Palaeozoic through the Mesozoic.

As far north as the gorge of the Missouri river in Montana, the Front range, facing the Great Plains, is a rather simple uplift, usually formed by upturning the flanking strata, less often by a fracture.

The idea is still better confirmed farther north in Wyoming, where the Laramie Range, flanked with upturned strata on the east and west, is for the most part a broad upland at altitudes of 7000 or 8000 ft., with no strong surmounting summits, and as yet no deep carved valleys.

This low range turns westward in a curve through the Rattlesnake Mountains towards the high Wind River Mountains (Gannett Peak, 3,775 ft.), an anticlinal range within the body of the mountain system, with flanking strata rising well on the slopes.

Flanking strata are even better exhibited in the Bighorn Mountains, the front range of northern Wyoming, crescentic in outline and convex to the northeast, like the Laramie Range, but much higher; here heavy sheets of limestone arch far up towards the range crest, and are deeply notched where consequent streams have cut down their gorges.

Farther north in Montana, beyond the gorge of the Missouri river, the structure of the Front Range is altogether different; it is here the carved residual of a great mass of moderately bent Palaeozoic strata, overthrust eastward upon the Mesozoic strata of the plains; instead of exposing the oldest rocks along the axis and the youngest rocks low down on the flanks, the younger rocks of the northern range follow its axis, and the oldest rocks outcrop along its eastern flanks, where they override the much younger strata of the plains; the harder strata, instead of lapping on the mountain flanks in great slab-like masses, as in the Bighorns, form out-facing scarps, which retreat into the mountain interior where they are cut down by outfiowing streams.

Each escarpment stands forth where a resistant formation overlies a weaker one; each escarpment is separated from the next higher one by a broad step of weaker strata.

Over the interior the strata are nearly horizontal, but in the mountain regions of the east and west, as well as in the mountains of Arkansas and Oklahoma, they are tilted and folded, and locally much metamorphosed.

The explanation of the apparent conformity of the strata from the Cambrian to the Pennsylvanian in some parts of the west, with no fossils defining with certainty any horizon between the Ordovician and the Mississippian, is one of the open problems in the geology of the United States.

The strata are now tilted and much faulted, though but little folded.

If maximum thicknesses of its several parts in different localities, as usually measured, are added together, the total would approach or reach 25,000 ft.; but the strata of any one region have scarcely more than half this thickness, and the average is much less.

The lode was an ore channel of great dimensions included within volcanic rocks of Tertiary age, themselves broken through pre-existing strata of Triassic age, and exhibited some of the features of a fissure vein, combined in part with those of a contact deposit and in part with those of a segregated vein.

These strata have been subjected to great denudation, but owing to their comparatively soft character this has been, in the main, nearly uniform, and has produced no very bold features of relief.

Many indications of ice action are found in these islands; striated surfaces are to be seen on the cliffs in Eday and Westray, in Kirkwall Bay and on Stennie Hill in Eday; boulder clay, with marine shells, and with many boulders of rocks foreign to the islands (chalk, oolitic limestone, flint, &c.), which must have been brought up from the region of Moray Firth, rests upon the old strata in many places.

In 1849 he became curator of the Natural History Museum at Wiesbaden, and began to study the Tertiary strata of the Mayence Basin, and also the Devonian fossils of the Rhenish provinces, on which he published elaborate memoirs.

The conquered strata of the population speak servile Indian dialects, called Hindki in the north and Jatki in the south, while Gujari is spoken by the large Gujar population in the hills of Hazara and north of Peshawar.

Clew Bay, with its islets capped by glacial drift, is a submerged part of a synclinal of Carboniferous strata, and Old Red Sandstone comes out on the north side of this, from near Achill to Lough Conn.

It is one of the most important problems in ancient history to determine what was the ethnological relation of these tribes, whom we may call " Safine," to the people of Rome on the one hand, and the earlier stratum or strata of population in Italy on the other.

There is further an important piece of evidence which connects together all the Safine tribes and distinguishes them sharply, at least in the 5th and following centuries B.C., from the earlier strata of population in Italy.

Down to 1848, and even still later, " Democracy " was used to cover the whole mass of the people, pre-eminently represented by the broad strata of the bourgeoisie; in 1900 the Democratic party itself meant by this term the rule of the labouring class organized as a nation, which, by its numerical superiority, thrust aside all other classes, including the bourgeoisie, -and excluded them from participation in its rule.

The observations of Strachey, Godwin-Austen and of Griesbach and other members of the Geological Survey of India only extend to the southern edge or rim of the great plateau, where vast alluvial deposits in horizontal strata have been furrowed into deep ravines, while Russian explorers have but superficially examined the mountain regions of the north and north-east, and the British mission to Lhasa, in 1904 afforded observations merely along the trade-route to that city.

Every river which rises in Tibet washes down sands impregnated with gold, and it has been proved that this gold is not the product of intervening strata, but must have existed primarily in the crystalline rocks of the main axes of upheaval.

On the basis of his results, as they have been scrutinized by scholars like Schiirer and Geffcken, it is possible to disentangle some of the different strata with a certain degree of confidence.

The influx of base European strata helped to reduce the whole continent south of Mexico in about a century to a level as low as that preceding the first mission.

He described also the graptolites of the local Silurian strata; and the.

Conybeare in 1821 to the coal-bearing strata of England and Wales, including the related grits and limestones immediately beneath them.

The term is a relic of that early period in the history of stratigraphy when each group of strata was supposed to be distinguished by some peculiar lithological character.

The so-called " unproductive " or barren strata, that is, those without workable coals, are not always limestones; quite as often they are shales, red sandstones and red marls.

In subdividing the strata of the Carboniferous system and correlating the major divisions in different areas, just as in other great systems, use has to be made of the fossil contents of the rocks; stratigraphical units, based on lithology, are useless for this purpose.

The sequence of Carboniferous strata is not everywhere one of unbroken continuity.

Flowing in a deep bed cut in the tuff strata, the river is not navigable.

In the river-beds, however, and at some distance from the sea, older strata and eruptive rocks underlie the alluvium.

The principal sea-inlets in the north are the Texel Gat or Marsdiep and the Vlie, which lead past the chain of the Frisian Islands into the large inland sea or gulf called the Zuider Zee, and the Wadden or " shallows," which extend along the shores of Friesland and Groningen as far as the Dollart and the mouth of the Ems. The inland sea-board thus formed consists of low coasts of sea-clay protected by dikes, and of some high diluvial strata which rise far enough above the level of the sea to make dikes unnecessary, as in the case of the Gooi hills between Naarden and the Eem, the Veluwe hills between Nykerk and Elburg, and the steep cliffs of the Gaasterland between Oude Mirdum and Stavoren.

In many cases the swollen cell-walls serve as reserves, and sometimes the substance is so thickly deposited in strata as to obliterate the lumen, and the hyphae become nodular (Polyporus sacer, P. rhinoceros, Lentinus Woermanni).

Meanwhile differences in consistency appear in various strata, and a dense outer protective layer (peridium), soft gelatinous layers, and so on are formed, the whole eventually attaining great complexity - e.g.

As the drainage by cuniculi removed the moisture in the subsoil, so the drainage of the lakes by emissaria, outlet channels at a low level, prevented the permeable strata below the tufa from becoming impregnated with moisture which they would otherwise have derived from the lakes of the Alban Hills.

From the slope of the strata from one central point in the Val del Bue he further concluded that there once existed a second great crater of permanent eruption.

In the Ardennes the rocks which constitute the ancient mountain chain belong chiefly to the Devonian System, but Cambrian beds rise through the Devonian strata, forming the masses of Rocroi, Stavelot, &c., which appear to have been islands in the Devonian sea.

One of the simplest illustrations of the rectilinear flow of heat is the steady outflow through the upper strata of the earth's crust, which may be considered practically plane in this connexion.

For this reason observations at different depths in the same locality often give very concordant results for the same period, as the total percolation and the average rate are necessarily nearly the same for the various strata, although the actual degree of wetness of each may vary considerably.

In any case, it is evident that the transmission of heat by percolation would be much greater in porous soils and in the upper layers of the earth's crust than in the lower strata or in solid rocks.

Nothing more solid than strata of sand and mud is to be found for more than 200 ft.

Geology.Germany consists of a floor of folded Palaeozoic rocks upon which rest unconformably the comparatively little disturbed beds of the Mesozoic system, while in the North German plain a covering of modern deposits conceals the whole of the older strata from view, excepting some scattered and isolated outcrops of Cretaceous and Tertiary beds.

The mountain range that runs out towards the north-east of Sicily is composed of crystalline rocks precisely similar to those forming the parallel range of Aspromonte in Calabria, but both of these are girt about by sedimentary strata belonging in part to an early Tertiary epoch.

In its population, too, Alexandria was only semi-Hellenic; for besides the proportion of Egyptian natives in its lower strata, its commercial greatness drew in elements from every quarter; the Jews, for instance, formed a majority of the population in two out of the five divisions of the city.

Whilst the upper classes in Italy absorbed Greek influences by their education, by the literary and artistic tradition, the lower strata of the population of Rome became largely hellenized by the actual influx on a vast scale of Greeks and hellenized Asiatics, brought in for the most part as slaves, and coalescing as freedmen with the citizen body.

Formed mostly of horizontal strata of varying hardness, they present a series of terraces of minor plateaus, rising one above the other, and intersected by small ravines worn by the occasional rainstorms which burst in their neighborhood.

Miocene strata are absent in the southern Tertiary areas, but are present at Moghara and in the north.

Marine Pliocene strata occur to the south of the pyramids of Giza and in the Fayum province, where, in addition, some gravel terraces, at a height of 500 ft.

There the boulder clay lies immediately on the primitive rock, except in the south-western corner of the island, where a series of strata appear belonging to the Cambrian, Silurian, Jurassic and Cretaceous formations, the true Coal formation, &c., being absent.

Such beds of salt are found in strata of very varied geological age; the Salt Range of the Punjab, for instance, is probably of Cambrian age, while the famous saltdeposits of Wieliczka, near Cracow, have been referred to the Pliocene period.

Deeper down there are successively strata of polyhalite, MgS04 K2S04.2CaS04.2H20, and anhydrite, CaSO 4, interspersed with regular layers of rock-salt; whilst below the anhydrite we have the main rock-salt deposits.

Important deposits of salt are developed in many parts of the Tertiary strata.

Cubic pseudomorphs representing rock-salt are sometimes seen in strata which have been deposited in shallow water, especially on the margin of a salt-lake.

In Cheshire the surface-water trickling through the overlying strata dissolves the salt, which is subsequently pumped as brine, but at Middlesbrough the great depth and impermeability of the strata precludes this, so another method has been resorted to.

Finally, beyond the Balkans lies the great Rumanian depression, occupied chiefly by undisturbed Cretaceous and Tertiary strata.

Hence their line of trend, which like that of all the other strata is in a north-easterly direction, may be traced from hill to hill by their more craggy contours.

Primary deposits are doubtfully represented by the detached fragments of unfossiliferous strata of Traras, Blida and east of Orleansville.

When the two lowlands are traced eastward they become confluent after the Niagara limestone has faded away in central New York, and the single lowland is continued under the name of Mohawk Valley, an east-west longitudinal depression that has been eroded on a belt of relatively weak strata between the resistant crystalline rocks of the Adirondacks on the north and the northern escarpment of the Appalachian plateau (Catskills-Helderbergs) on the south; forming a pathway of great historic and economic importance between the Atlantic seaports and the interior.

A wonderful series of these forms occurs in southern Utah, where in passing northward from the Carboniferous platform one ascends in succession the Vermilion Cliffs (Triassic sandstones), the ViThite Cliffs (Jurassic sandstones, of remarkably cross-bedded structure, interpreted the dunes of an ancient desert), and finally the Pink Cliffs (Eocene strata of fluviatile and lacustrine origin) of the high, forested plateaus.

During the current cycle of erosion, several of the faults, whose scarps had been worn away in the previous cycle, have been brought to light again as topographic features by the removal of the weak strata along one side of the fault line, leaving the harder strata on the other side in relief; such scarps are known as fault-line scarps, in distinction from the original fault scarps.

The Triassic system is well developed on the Pacific coast, where its strata are of marine origin, and they extend inland to the Great Basin region.

In the south-western parts a succession of strata, described as the Brown Coal or Lignite formations, intervenes between the chalk and the boulder clay; its name is derived from the deposits of lignite which occur in it.

This mass had buried a great part of the Lydian and Greek cities, but on a protected slope some undisturbed Lydian strata were found.

The highest summit in the south of Scotland - Merrick (2764 ft.) - consists of Silurian strata much altered by proximity to the granite, while the rest of the more prominent heights (all in Kirkcudbrightshire) - Rinns of Kells (2668 ft.), Cairnsmuir of Carsphairn (2612), and Cairnsmore of Fleet (2331) - are formed of granite.

They constitute the lowest group of the most interesting series of strata in the Highlands, and yield a large number of fossils.

Those of Ayrshire and Galloway are lower and more accessible, and permit of study of the plication of the strata.

Such strata are well seen in the isle of Raasay and near Heast in Skye.

On the east side of Scotland, where so many fragments of the Secondary rocks occur as boulders in the glacial deposits, a large mass of strata was formerly exposed at Linksfield to the north of Elgin, containing fossils which appear to show it to belong to the Rhaetic beds at the top of the Trias.

Rhaetic strata no doubt exist in situ at no great distance under the North Sea.

Along the east coast of Sutherland good sections are exposed showing the succession of strata.

They are prolonged southwards into Antrim, where similar basalts overlying Secondary strata cover a large territory.

The presence of these fossils indicates that the eruptions were subaerial, and a comparison of them with those elsewhere found among Older Tertiary strata shows that they probably belong to the Oligocene stage of the Tertiary series of formations, and therefore that the basalt eruptions took place in early Tertiary time.

Fossil as well as living animals engaged his attention, and in his studies of the strata around Paris he was instrumental in establishing the Tertiary formations.

The great mass of the people were distinguished quite roughly into four classes, social strata, of which the boundary lines were vague and uncertain.

The clear atmosphere is in its upper strata free from clouds and dust, so that the sun's rays undergo scarcely any absorption and strike down with full force on the light-brown desert soil, from which they are radiated and reflected to a great extent.

Fars series; marls, clays and sand stones with limestones and inter bedded strata of rock gypsum.

Although it has the deciduous dentition, Mme Pavlow considers herself justified in referring the Kherson skull to the genus Procamelus previously known only from the Lower Pliocene or Upper Miocene strata of North America, and differing from modern camels, among other features, by the retention of a fuller series of premolar teeth.

Be this as it may, the identification of a North American type of camel from the Tertiary strata of eastern Europe forms another connecting link between the extinct faunas of the northern half of the Old World and North America, and thus tends to show that the claim of America to be the exclusive birthplace of many Old World types may have to be reconsidered.

Remains of camels (C. thomasi) have also been found in the Pleistocene strata of Oran and Ouen Seguen, in Algeria; and certain remains from the Isle of Samos have been assigned to the same genus, although the reference requires confirmation.

Geologically the group is composed mainly of Triassic, Cretaceous and Tertiary strata, penetrated by intrusive rocks.

Between these two distinct strata there is a gap, through which persons on a vessel near the island may obtain a glimpse of the peak.

It is composed of horizontal strata of limestone, forming groups of hills intersected by a network of small and fertile valleys.

Lower Palaeozoic strata lap up on to the crystalline rocks on all sides of the mountain group. The region is rich in magnetic iron ores, which though mined for many years are not yet fully developed.

These beds are conformably succeeded, along the Central Asian watershed, by a continuous series of strata which apparently represent the Permian, Trias and Jurassic of Europe.

In the former even the Pliocene beds are crumpled and folded, overfolded and overthrust in the most violent fashion; in the latter none but the oldest beds, certainly none so late as the Permian, have been crumpled or crushed - occasionally they are bent and frequently they are faulted, but the faults, though sometimes of considerable magnitude, are simple dislocations, unaccompanied by any serious disturbance of the strata.

Upon them rest the unfossiliferous strata known to Indian geologists as the Transition and Vindhyan series.

At the present day the only place where the search for diamonds is pursued as a regular industry is the native state of Panna in Bundelkhand The stones are found by digging down through several strata of gravelly soil and washing the earth.

The littoral zone contains the only fossiliferous strata.

Fossil remains of extinct civets are found in the Miocene strata of Europe.

The exact form of the sanctuary at that period cannot be determined, but it seems to have been in some way connected with the burning of the dead, and extensive remains of such cremation are found in all the earlier, pre-Sargonic strata.

In one of these earlier strata, of very great antiquity, there was discovered, in connexion with the shrine, a conduit built of bricks, in the form of an arch.

In this revolution the rise of the lower strata of the population to power played an important part.

The Lower Old Red Sandstone strata are separated from the foregoing series by a fault and form a curving belt extending from Corloch on the east coast south by Brodick Castle to Dougrie on the west shore.

The strata occur on the east shore between the Fallen Rocks and Corrie, and they appear along a narrow strip to the east and south of the lower division of the system, between Sannox Bay and Dougrie.

Here there is an ascending sequence from the Calciferous Sandstone, through the Carboniferous Limestone with thin coals formerly worked, to the Coal Measures, the strata being inclined at high angles to the north.

On the south side of a well-marked anticline in the Upper Old Red Sandstone at North Sannox, the Carboniferous strata reappear on the coast with a south dip showing a similar ascending sequence for about half a mile.

The small development of Upper Carboniferous strata, visible on the shore south of Corrie and in Ben Lister Glen, consists of sandstones, red and mottled clays and purple shales, which yield plantremains of Upper Carboniferous facies.

The second is represented by a thin lava, associated with the Upper Limestone group of the Carboniferous Limestone series, and the highest is found in Ben Lister Glen intercalated with the Upper Carboniferous strata, and may be the equivalent of the volcanic series which, in Ayrshire, occupies the position of the Millstone Grit.

At Corrie and the Cock of Arran they rest on Upper Carboniferous strata; in Ben Lister Glen, on the lower limestone group of the Carboniferous Limestone series; and on the west coast they repose on the Old Red Sandstone.

There is, therefore, a clear discordance between the Trias and all older strata in Arran.

The former extension of Rhaetic, Liassic and Cretaceous formations in the island is indicated by the presence of fragments of these strata in a large volcanic vent on the plateau, on the south side of the road leading from Brodick to Shiskine.

Erosion buttes and mesas occasionally rise as picturesque monuments above the general level of the plains, and in the vicinity of the mountains the plains strata, elsewhere nearly horizontal, are bent sharply upward and carved by erosion into " hogback " ridges.

The strata of this system rest upon the Pre-Cambrian, and are succeeded by the Ordovician system.

This fossil-bearing set of strata he first styled the "fossiliferous greywacke series," changing it in 1835 to "Silurian system."

These formations lie at the base of the lowest Cambrian strata and may possibly be included in the pre-Cambrian, though in Norway they are clearly resting upon a striated floor of crystalline rocks.

Wherever the Cambrian strata have been carefully studied it has now been found possible and convenient to arrange them into three series, each of which is characterized by a distinctive genus of trilobite.

It is true that these fossils are not invariably present in every occurrence of Cambrian strata, but this fact notwithstanding, the threefold division holds with sufficient constancy.

The table on p. 660 contains the names that have been applied to the subdivisions of the Cambrian strata in the areas of outcrop in Wales and England; at the same time it indicates approximately their relative position in the system.

Here the Cambrian system is only distinguished clearly on the eastern side, where the three subdivisions are found in a thin series of strata (400 ft.), in which black concretion-bearing shales play an important part.

Upper Cambrian strata have been found in upper Alemtejo in Portugal.

In the Thiiringer Wald are certain strata, presumably Cambrian since the uppermost beds contain the Euloma-Niobe fauna.

The Lower Cambrian has been found at various places in South Australia; and in Tasmania a thick series of strata appears to be in part at least of Upper Cambrian age.

Consequently, Cambrian strata are usually unconformable on older rocks.

The common occurrence of red strata has been cited in support of this view.

The like must be said even of the contribution to the problem made by August Pott,' though he has helped to define one condition of success - the classification of the strata in " Western " texts - and has taken some steps in the right direction, in connexion with the complex phenomena of one witness, the Harklean Syriac.

Be this as it may, the physical appearance of the population of this central region of northern India - Hindustan and Behar - clearly points to an intermixture of the tall, fair-coloured, fine-nosed Aryan with the short-sized, dark-skinned, broad-nosed Dravidian; the latter type becoming more pronounced towards the lower strata of the social order.'

The Elk range is geologically interesting for the almost unexampled displacement of the strata of which it is composed, and the apparent confusion which has thence arisen.

Specimens of Latinized names in connexion with ecclesiastical foundations are preserved in Strata Florida and Valle Crucis Abbeys.

In 1238 Llewelyn, growing aged and infirm, summoned all his vassals to a conference at the famous Cistercian abbey of Strata Florida, whereat David, his son by the Princess Joan of England, was acknowledged his heir by all present.

Such an irregular distribution of the bath, with strong copper sulphate solution from the anode at the bottom and acid solution from the cathode at the top, not only alters the conductivity in different strata and so causes irregular current-distribution, but may lead to the current-density in the upper layers being too great for the proportion of copper there present.

The metalliferous deposits have generally the form of beds or layers between the strata of granulite and limestone.

The whole of the island of Oland consists of these strata.

In the western and northern alpine part of Sweden, near the boundaries of Norway, the Silurian strata are covered by crystalline rocks, mica schists, quartzites, &c., of an enormous thickness, which have been brought into their present positions upon a thrust-plane.

These earthquake shocks have two distinct characteristics, a slight vibration, sometimes almost imperceptible, called a temblor, generally occurring at frequent intervals, and a violent horizontal or rotary vibration, or motion, also repeated at frequent intervals, called a terremoto, which is caused by a fracture or displacement of the earth's strata at some particular point, and often results in considerable damage.

The whole of the north part of Tierra del Fuego is occupied by plateaus of horizontal Tertiary strata.

They are not confined to any one horizon, but occur irregularly throughout the Jurassic and occasionally also amongst the Cretaceous strata.

The latter are usually described as mountain ranges, but they are, in fact, only the remains of the ancient plateau, capped with horizontal strata of sandstone, and having a remarkably uniform altitude of 2000 to 2400 ft.

Auriferous alluvial strata have been discovered in various localities, but everywhere the scarcity of water has been a bar to their being exploited with profit.

The genus was represented in the Tertiary flora of Europe, when it extended into the polar regions; nineteen species have been recorded from the Miocene strata of Oeningen in Switzerland.

Matters got to such a climax of disorder, disturbance and confusion, from the highest to the lowest strata of Spanish society, that the president of the executive, Figueras, deserted his post and fled the country.

Between the folded marine beds of the Himalaya and the nearly horizontal strata of the peninsula lies the Indo-Gangetic plain, covered by an enormous thickness of alluvial and wind-blown deposits of recent date.

These chapters present considerable difficulty to the literary critic; for while they clearly illustrate the application of the principle of " holiness," and in the main exhibit the characteristic phraseology of II, they also display many striking points of contact with P and the later strata of P, which have been closely interwoven into the original laws.

If the thickness of the film is greater than 2E, there will be a stratum of thickness c-2E in the middle of the film, within which the values of p and x will be pc and In the two strata on either side of this the law, according to which p and x depend on the depth, will be the same as in a liquid mass of large dimensions.

The membrane may be relatively thick, and even exhibit shells or strata.

Beyerinck and Jegunow have shown that some partially anaerobic sulphur bacteria can only exist in strata at a certain depth below the level of quiet waters where SH 2 is being set free below by the bacterial decompositions of vegetable mud and rises to meet the atmospheric oxygen coming down from above, and that this zone of physiological activity rises and falls with the variations of partial pressure of the gases due to the rate of evolution of the SH 2.

The strata are thrown into folds which run in the direction of the mountain ridges, forming a curve with the convexity facing the south-east.

The process of destruction, slow in some places, is so rapid in others that it can be traced even from month to month - the incessant work of the waves washing away the soft strata at the base of the cliffs and leaving the summits unsupported.

In exactly the same way the whole of the south-east of the island appears to have been covered uniformly with gently dipping beds of Tertiary sands and clays, beneath which the Cretaceous strata dipped.

In these hollows the Tertiary rocks were protected from erosion, and remain to form the London and the Hampshire Basins respectively, while on the anticlinal axis the whole of the Tertiary and the upper Cretaceous strata have been dissected away, and a complex and beautiful configuration has been impressed on the district of the Weald.

The whole region may be looked upon as formed by an arch or anticline of Carboniferous strata, the axis of which runs north and south; the centre has been worn away by erosion, so that the Coal Measures have been removed, and the underlying Millstone Grit and Carboniferous Limestone exposed to the influences which form scenery.

On both sides of the arch, east and west, the Coal Measures remain intact, forming outcrops which disappear towards the sea under the more recent strata of Permian or Triassic age.

The group of heights of South Wales, running on the whole from west to east, marks the outcrops of the Old Red Sandstone and Carboniferous strata which lie within a vast syncline of the Silurian rocks.

The outer rim of the Welsh area contains a broken series of coal-fields, where patches of Carboniferous strata come to the surface on the edge of the New Red Sandstone plain.

The peninsula of Cornwall and Devon may be looked upon as formed from a synclinal trough of Devonian rocks, which appear as plateaus on the north and south, while the centre is occupied by Lower Carboniferous strata at a lower level.

The Devonian strata on the south do not form such lofty elevations as those on the north, and are in consequence, like the plain of Hereford, very fertile and peculiarly adapted for fruit-growing and cider-making.

The great variety of the rocks which meet the sea along the south of Cornwall and Devon has led to the formation of a singularly picturesque coast - the headlands being carved from the hardest igneous rocks, the bays cut back in the softer Devonian strata, The fjord-like inlets of Falmouth, Plymouth and Dartmouth are splendid natural harbours, which would have developed great commercial ports but for their remoteness from the centres of commerce and manufactures.

Smaller patches of the Coal Measures appear near Tamworth and Burton, while deep shafts have been sunk in many places through the overlying Triassic strata to the coal below, thus extending the mining and manufacturing area beyond the actual outcrop of the Coal Measures.

A few small outcrops occur where still more ancient strata have been raised to the surface, as, for instance, in Charnwood Forest, where the Archaean rocks, with intrusions of granite, create a patch of highland scenery in the very heart of the English plain; and in the Lickey Hills, near Birmingham, where the prominent features are due to volcanic rocks of very ancient date.

The Eastern Division is built up of parallel strata, the edges.

From the upland of Salisbury Plain, which corresponds to the axis of the anticline marking the centre of the double fold into which the strata of the south of England have been thrown, the great Chalk escarpment runs north-eastward; fingers of Chalk run eastward one each side of the Weald, forming the North and South Downs, while the southern edge of the Chalk sheet appears from beneath the Tertiary strata at several places on the south coast, and especially in the Isle of Wight.

The boundaries of the parishes, the fundamental units of English political geography, are very often either rivers or watersheds, and they frequently show a close relation to the strike of the geological strata.

Its central core of Lower Carboniferous rock is broadly displayed towards the north, while southward it contracts; on either side lie the younger rocks, the coal-fields, the Permian strata and the Triassic formations, the last-named, while sweeping round the southern extremity of the Carboniferous axis of the uplift from its eastern and western flanks, spread out in a large sheet over the midland counties.

The strata are folded so as to form a fan.

They are overlain by the fossiliferous limestones of the Antalo group. Around Chelga and Adigrat coal-bearing beds occur, which Blanford suggests may be of the same age as the coalbearing strata of India.

The substratum of the island is Kimeridge Clay, above which rests beds of sand and strata of Oolitic limestone, widely famed as a building stone.

In the "dirt-bed" resting upon the Oolitic strata numerous specimens of petrified wood are found, some of great size.

In later years he gave special attention to the Tertiary strata, including the Brown Coal of North Germany.

In 1854 he proposed the term Oligocene for certain Tertiary strata intermediate between the Eocene and Miocene; and the term is now generally adopted.

A wellknown fossil conifer from Triassic strata - Voltzia heterophylly - also illustrates a marked dissimilarity in the leaves of the same shoot.

Buhrstone, a cellular variety of chalcedonic quartz from the Tertiary strata of the Paris basin, is largely used for millstones.

The third zone covers the higher mountains on their southern and eastern sides, whose violently contorted strata leave many transverse valleys, though usually inclining laterally towards the south-east.

Along the foot of the Carpathians lies a broad trough of Miocene salt-bearing beds, and in this trough the strata are sometimes horizontal and sometimes strongly folded.

The group is typified by Chalicotherium, of which the original species was discovered in the Lower Pliocene strata of Eppelsheim, Hesse-Darmstadt, in 1825, and named on the evidence of the teeth, the limbs being subsequently described as Macrotherium.

Remains referred to Chalicotherium have been also obtained from the Lower Pliocene and Upper Miocene strata of Greece, Hungary, India, China and North America.

In the outer strata a different state must prevail.

The absence of lines of the spectrum of any element from the solar spectrum is no proof that the element is absent from the sun; apart from the possibility that the high temperature and other circumstances may show it transformed into some unknown mode, which is perhaps the explanation of the absence of nitrogen, chlorine and other non-metals; if the element is of high atomic weight we should expect it to be found only in the lowest strata of the sun's atmosphere, where its temperature was nearly equal to that of the central globe, and so any absorption line which it showed would be weak.

Owing, however, to the very variable permeability of the strata, the tributaries of the Thames, when separately gauged in dry seasons, yield the most divergent results.

The positions of springs are determined by permeable depressions in the surface of the ground below the general level of saturation, and frequently also by the holding up of that level locally by comparatively impermeable strata, sometimes combined with a fault or a synclinal fold of the strata, forming the more permeable portion into an underground basin or channel lying within comparatively impermeable boundaries.

Hence the best position for a well in the Chalk is generally that over which, if the strata were impermeable, the largest quantity of surface water would flow.

The formation is probably more or less permeable throughout; it consists largely of loose sand and takes the general south-easterly dip of British strata.

If the strata were uniformly porous the water would lie in the rock at different depths below the surface according to the previous quantity and distribution of the rainfall.

Precisely the same thing happens in the actual crust of the earth, except that, in the formations usually met with, the strata are so irregularly permeable that no such uniform percolation occurs, and most of the water, instead of oozing out near the sea-level, meets with obstructions which cause it to issue, sometimes below the sea-level and sometimes above it, in the form of concentrated springs.

On the upheaval of such rocks above the sea-level, fresh water from rainfall began to flow over their exposed surfaces, and, so far as the strata were permeable, to lie in their interstices upon the salt water.

Where the strata are not uniformly porous, they may resist the passage of water from the direction of the sea or they may assist it; and round the whole coast of England, in the Magnesian limestone to the northeast, in the Chalk and Greensand to the east and south, and in the New Red Sandstone to the west, the number of wells which have been abandoned as sources of potable supply, owing to the percolation of sea water, is very great.

Even the beds of sluggish rivers flowing over porous strata generally become so impermeable that excavations made in their neighbourhood, though freely collecting the subsoil water, receive no FIG.

It is not always possible to prevent any leakage whatever through the strata below the bottom or beyond the ends of the trench, but it is always possible to render such leakage entirely harmless to the work above it, and to carry the water by relief-pipes to visible points at the lower toe of the dam.

There are four distinct strata in the cave.

In every instance therefore where, in walking over the surface, we traverse a series of strata which gradually, and without dislocations, increase or diminish in inclination, we cross part of a great curvature in the strata of the earth's crust.

The strata must once have risen above the present surface, and in many cases may be found descending to the surface again with a contrary dip, the intervening portion of the undulation having been worn away.

The curvature occasionally shows itself among horizontal or gently inclined strata in the form of an abrupt inclination, and then an immediate resumption of the previous flat or sloping character.

The strata are thus bent up and continue on the other side of the tilt at a higher level.

It much more frequently happens that the strata have been bent into arches and troughs, so that they can be seen dipping under the surface on one side of the axis of a fold, and rising up again on the other side.

On the east side of the axis the strata follow each other in regular succession as far as No.

Such foldings of strata must always die out unless they are abruptly terminated by dislocations.

The observer in passing northwards along the axis of that anticline finds himself getting into progressively higher strata as the fold sinks down.

In the majority of folds the bending of the strata has taken place about an "axial plane" (often called the "axis"), which in the examples illustrated in fig.

The heterogeneous character of great masses of strata has always had a marked influence on the nature of the folding; some beds have yielded much more readily than others, certain beds will be found to be faulted, .while those above and below have folded without fracture.

Near the crest of anticlines is commonly an enriched portion of the ground in mineralized districts; and, in the case of water supply, the tilt of the strata determines the direction of the underground flowage.

There can be no doubt that the first effect of the Conquest was that the upper strata of the agricultural classes lost the comparative independence which they had hitherto enjoyed, and were in many cases depressed to the level of their inferiors.

These strata are practically stagnant, deficient in oxygen and surcharged with carbonic acid.

The Harz is a mass of Palaeozoic rock rising through the Mesozoic strata of north Germany, and bounded on all sides by faults.

Representatives of all the Tertiary formations are met with in Turkestan; but while in the highlands the strata are coast-deposits, they assume an open sea character in the lowlands, and their rich fossil fauna furnishes evidence of the gradual shallowing of that sea, until at last, after the Sarmathian period, it became a closed Mediterranean.