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NATIONAL GEOGRAPHIC SOCIETY

GARDINER O. III-BBARD, PRESIDENT

THE PHYSIOGRAPHY

OP Tine

UNITED STATES

TEN MONOGRAPHS IsV .T. W. POWKl.L, X. S. KIIALEIi, I. C. RVSSELL, nAILF.Y WILLIS, ('. WILLAIU> HAYES, J. S. DILLKR, \V. M. UAVIS, O. K. (ilLBERT.

NEW YORK • : • CINCINNATI • : • CHICAGO

AMERICAN BOOK COMPANY

1897

Copyrit^ht, 1 S9G, by American Book Company.

^03

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PEEFACE.

The study of the origin of eartli forms lias made remark- able progi'ess dui-ing the last twenty years, so that it is scarcely exaggeration to say that a new science has been created. While those who have aided in its development are learned investigators exploring the frontiers of human knowledge, the more impoi'tant results are so simple as to be appreciated not only by intelligent lajnnen, but even by school children. Practical experiment has shown that the explanation of the work of rain and streams in the shaping of the eartli is one of the most attractive and fi-uitful nature studies which can be intro- duced into pi'imary and secondary schools, and a move- ment has been organized among educators for its extensive introduction. Professor W. M. Da\ds of Harvard Uni- versity, who is a leader in this movement, proposed about two years ago that the National Greographic Society undertake the preparation of a series of essays on geo- graphic sul)jects, enlisting in the work some of the numerous specialists in its membership, and making such arrangements for puljlicatiou that the essays should be accessible to the teachers of the land. This ])roposition was developed and discussed at a conference held in Washington in June, 1894, and a few months later the managers of the society took action, appointing an editing committee under the chairmanship of Major J. W. Powell. AiTangements for publication were made with the Amer- ican Book Company, and this volume is the first product of that cooperation.

CONTENTS,

PAGE

Physiographic Processes 1

By J. W. PoweU. Physiographic Features 33

By J. W. Powell. Physiographic Regions of the United States 65

By J. W. Powell. Present and Extinct Lakes op Nevada 101

By I. C. Russell. Beaches and Tidal Marshes ok the Atlantic Coast . . . .137

By N. S. Sbaler. The Northern ^^palachians 169

By Bailey Willis. Niagara Falls and their History 203

By U. K. Gilbert. Mount Shasta, a Typical Volcano 237

By J. S. Diller. "

The Physical Geography of Southern New England .... 269

By W. M. Duvis.

The Southern Appalachians 305

By C. Willard Hayes.

PHYSIOGRAPHIC PROCESSES.

By J. W. Powt:ll.

Physiography is a description of the surface features of the earth, as bodies of air, water, and laud. lu it is usually included an explanation of theu* origin, for such featui'es are not properly understood without an explanation of the processes by which they are formed.

The earth has three moving envelopes. These are, first, the atm.osj)here, which covers it to a great depth ; second, the water, which covers more than three fourths of its surface with sea, lake, stream, and ice field, while the whole is covered intermit- tently with clouds ; and, third, a garment of rock in beds, layers, and piles.

These outer, middle, and inner garments of air, water, and rock are forever in motion. Each envelope has a system of mo- tions of its own, j'et all three act and react upon one another in such a manner, that, wliile their motions are independent in part, they are at the same time interdependent in part.

Within the envelopes is the great central body of the earth, which is but little known, but about which there has been mudi speculation. Many scientific men believe it to be solid, and deem that this is proved from certain evidence dei-ived from the tides ; other scientific men believe that the interior of the earth is in a sublluid condition, due to the pressure of the superincumbent envelope of rock. For present pui'poses it is unnecessary to weigh the evidence for these two hypotheses and judge between them. Wliat we need is to imderstand clearly that there are three pretty well defined envelope's tliat are in motion, and ever interacting among themselves in sucli a manner, that there are sea bottoms, plains, plateaus, mountains, hills, and valleys in the rock envelope ; there are seas, lakes, sti-eams, and clouds in the aqueous envelope ; and there are winds in the atmospheric en- velope ; and that the winds, clouds, storms, streams, lakes, seas,

(Copyright, 1895, by American Book Company.)

2 PHYSIOGRAPHIC PROCESSES.

^silleys, hills, mountaius, plateaus, plaius, aud sea floors are all

related to one another, aud ahvays chaugiiig. That which is sea

floor at oue time is plaiu at another, phiteau at still another,

mouutaiu summit at stiU another ; and hills aud valleys follow

in succession, for the land seems to be always rising and faUiug.

Another gi-eat fact requires mention in this place. It is

generally beheved that the earth is surrounded by and pei--

meated with an ether which extends in space through the solar

system and into the region of fixed stars. By means of this

ether the earth is m constant communication with the moon,

X the sun, every planet, and every distant orb, and through it

. comes to the earth a constant flow of light and heat from the

1 fiery globes of space.

THE ATMOSPHERIC ENVELOPE.

Changes in the air come chiefly in four ways: —

First, It moves with the rest of the earth, of which it forms a part, in rotation about the central axis.

Second, Being heated at the tropics and cooled in the polar regions, the air about the equator rises, and flows poleward in both dii-ections. In the polar regions the air, being cooled, sinks, and flows toward the ecpiator. The gi'eat velocity of the winds in equatorial regions as they are carried eastward with the rotat- ing earth, and the small velocity of the polar -n-inds due to the same cause, interact with the polar-equatorial currents, so that the air flowing toward the jwles is turned eastward, while the air flowing toward the equator is turned westward.

Third, The vapor of water from the surface of the sea and land is carried in the clouds by the winds, aud from time to time is discharged from the air as rain. In this discharge gi-eat changes of temperature are involved, and vertical currents of air are thus set up which greatly modify the direction and velocity of the ^vinds.

Fourth, The surface of the land affects the dii-ection of the lower winds: for mountains change the direction of air cui-reuts; hills turn the winds through valleys ; and cliffs, banks, ledges, and rocks produce eddies in the lower atmosphere.

The effect of these four processes is to make the winds seem fickle, and yet they are ever obeying law.

Above the surface of the earth the winds become more con-

THE AQUEOUS ENVELOPE. 3

staut as they are more and more governed by the gi'eat laws which change with the hours of the day and the seasons of the year.

Climatic temperature is the temperature of the air, measured in the shade so as to avoid the direct radiation of th<> sun. This temperature decreases from the equator to the poles. Thus there is a latitudinal change of temperature. Other things being equal, the higher the latitude the cooler the air.

The earth revolves on its axis, which gives us day and night. The air is warmer by ilay and cooler l)y night.

Then the axis of the earth, about which it revolves in its daily rotation, is inclined to the plane of the orbit of the earth in its revolution about the sun ; for this reason the poles are turned alternately toward the sun, and tliis produces a summer and winter every year.

Temperatvu'e has still another variable, which is of great im- portance in the study of climate : tliis is altitude, or tlic elevation of the land above the level of the sea. In ascending througli the air in a baUoon, it is found to be cooler as the aerial voyager rises ; so in ascending from plains to plateaus the upper regions are found to be cooler, and in climbing from valley to hill and from hill to mountain a like change of temperature is oliserved. The summits of many high mountains of the world are in regions of perpetual snow and ice.

Thus there is latitudinal, diurnal, seasonal, and altitudiual variability of temperature, and to all of these must be added the variability which arises with changing winds and conditions of moisture.

The diurnal and annual motions of the earth, and then- rela- tions to the movements in the air and ocean, is a subject so well taught in our schools that it need not be carefully treated here ; but reference is mjide to it for the purpose of sliowing the way in which it enters into the subject of physiography.

THE AQUEOUS ENVELOPE.

The envelope of water is changeable in a variety of ways: —

First, As the moon revolves about the (^arth from east to west,

gravity drives the water behind it, so that the tides roll their

waves against the eastern shores ; but as the moon proceeds, the

tides roll back eastward to beat in waves against the westei'u

4 PHYSIOGKArHIC PROCESSES.

shores. So with the revolving moon the tides sweep back and forth across the surface of the sea, and alternately lash the shores with their crested waves.

Second, Tlie seas are heated mider the tropics, and cooled in polar zones; so that the water of the equatorial regions, wanned and ox]»anded, flows over the surface northward and southward toward the pt)les, and the waters cooled in the polar regions sink, and flow toward the equator.

The varying rotational velocity of the earth's suiface at differ- ent latitudes — from the equator, wliere it is more than one thou- sand miles an hour, to the poles, where it is i)ractically nothing — interacts on flowing waters, as on the winds, and makes those which flow towai'd the poles turn to the eastward against the westward-facing shores. Bo all surface currents drift eastward in going toward the poles. The currents thus formed are deflected by continental shores and oljstriicting islands, so that currents more or less clearly defined are established in the sea, modified to some slight extent by the great gulfs and the outpouring rivers from the land Avhere the currents follow the shore.

ThinJ, The winds drifting over tlie sea beat its surface into waves. When the winds are lulled, the billows go to rest, and the sea is calm and glassy; Init when the storms rise, the billows rage.

Fourth, The heat of the sun and other bodies of space, aided by drying winds, evaporates the waters 'from the sea; and the vapor thus formed is drifted by the winds and gathered into clouds, and precipitated upon the earth, where it gathers again into rills, Itrooks, creeks, and rivers, to roll back into the sea.

Fifth, In high southern and northern latitudes, and at gi'eat altitudes in the temperate and torrid zones, the moisture in the atmosi)here is congealed, and falls to the earth as snow, and thus mantles the earth with a robe of ice. In high altitudes and lati- tudes the snow accumulates in excess of the evaporation mitil great ice fields are formed. Under pressure, ice flows in some I'espects like water, but very slowly. On tlu^ sunnnit of the mountains of tropical ami temperate regions such ice fields are formed, filling the goi'ges, and extending over the crags and peaks. in high latitudes at the north and at the south, gi'eat ice fields accumulate on the plains and plateaus, as well as on the moun- tains, and glaciers of vast extent are thus formed. The ice-cov- ered area about the poles is variable. In some regions and at

RAINFALL, O

.some times it extends farther toward the temperate zone, while in otlier regions and at other times the ice field retreats.

Waters have constant mentions and variable motions. The tides are somewhat constant, and yet somewhat varialjle ; the waves have elements of constancy and elements of variability ; the clouds, in so far as they depend on evapoi-ation, have ele- ments of constancy and elements of varialnlity, derived from the exposure of surfaces to the sun and constant and variable winds. After the water has been evaporated in the heavens, it drifts with the winds, which are in part constant and in part vai-iable. The waters, like the winds, are modified l»y the rocky envelope; for, though largely under the sea, it is in many regions but little below the surface of the sea, and influeuees its currents and the evaporation of its waters. Other portions of the rock envelope lie above the sea-level, as plains, plateaus, mountains, and hills, and by their geogi-aphical distribution break the course of the winds, and greatly influence both evaporation and precipitation. Lands gather the waters wliieli fall from the clouds into streams, which are governed by the land slopes until they empty into the sea. So the winds influence the waters, and the waters influ- ence the winds, and the rocks influence the waters and the winds, and the winds and waters influence the rocks. All — rock, water, and air — are ever in motion, governed in part by constants and in part by variables.

Rainfall. — The evaporation of water from the surface of the earth is very irregular. In general there is more evaporation from water surfaces than from land surfaces, more in dry weather than in wet weather, more in hot weather than in cold weathei", and more in high winds than in calms. As the water is evap- orated from the sea and the land, it is carried away in the air to form clouds, which arc in part gathered Ity diverse winds, and in jjart directed by diverse lands into diverse regions. It is in this manner that the water is precipitated from the clouds irreg- ularly over the surface of the earth, some regions receiving more, other regions less, while in every region the rain is intermittent. A great rainstorm may come at one time, and a great drought at another: now the lands are flooded, and then the lands are parched. There are regions of the earth where the ainiual rainfall is more than six hundred inches, an<l there are other regions where the ; annual I'ainfall is not more than three inches. Thus in passing from land to land great irregularity of rainfall is discovered. But

6 PHYSIOGEAPHIC PROCESSES.

within the same laud there is vaiiability from time to time. Max- iimiui storms may jjive more than twenty inches of rain, wliile that given by niinimmu storms cannot even be measnred iu inches, the iniit is too large ; a mere dampening of the smface results therefrom.

Run-off. — The land is everywhere traversed by a netwoi'k of streams — as rivers, creeks, and brooks — which meander from tlie highlands down the vallej^s, little and great, uniting again and again, until as rivers they roll into the sea.

In lands of great rainfall the streams are many and large, whereas in lauds of small raiufall the streams are fewer and smaller ; but the decrease iu the number and size of the streams is much greater than the decrease iu precipitation. Stream aridity is greater than atmospheric aridity, iu arid climates, where the rate of precipitation is less, the rate of evaporation is gi'eater; so that aridity promotes evaporation, and thus still more diminishes the size and number of the streams. Under average conditions, where the mean annual rainfall is forty inches, about twenty inches of the precipitation is evapoi-ated from the surface of the land, and twenty inches is gathered into streams to be car)-ied away to lakes and seas. If the mean rain- fall is more than this, the mean run-off by streams is more tlinii half theruu-off; but if the mean raiufall is less, the mean run- off is less than hah' the rainfall. AVhere the raiufall is but ten inches anuuallj', permanent streams are not formed. "S\nien they are found in such regions, they have their sources iu other regions where the rainfall is greater. Other conditions being equal, the raiufall is greater about mountains, as moini- tains furnish conditions for increased precipitation. There are regions in the United States, as elsewhere in the world, where the raiufall is less than twenty inches, and where streams of water are gathered by mountains to roll down in deep rocky gorges. Such streams usually diminish in size as they procetnl, uutil their waters are evaporated. Often they end in luarshes and swampy lakes, where th(> sands are deposited by the djnug rivei's iuul creeks. Locally these are often called 6'w/r.s',- and many i)eople who do not understand the laws of evaporation, precipitation, and run-off, suppose that the streams actually sink beneath the surface of the earth, to flow in under- ground channels. There is a popular belief that there are many underground rivers of this character in the dry regions of the

FLOODS. 7

far West. In all regions thei*e are uudergi-ound waters, as the loose soils, sands, and gravels retain much water ; and the sands at the mouth of a vanishing stream also contain more or less subterranean water of this character, which is more slowly evap- orated into the heavens ; but these so-called lost rivers, carrjdng waters from moiintain streams of arid regions, do not exist, and the popular error in this respect has no foundation in fact. Yet there are lost rivers of another character, where streams disai)pear from the surface and run iu undergi'ound channels, to reappear below.

On the plains and in the valleys of regions where the annual rainfall is less than ten inches, or even less than three inches, intermittent streams ai'e sometimes formed. This little rain often comes in great storms, anil storm-water streams are thus produced, whose waters flow for a time as ci'eeks of mud, but are soon lost by evaporation. The mud which is thus swept down from the hills and higher ridges is deposited in the valleys Ix^low ; and gradually, through years and centuries, the valleys and low- lands are covered to great depths by such deposits.

In regions of country where the rainfall is twenty inches or more, permanent streams may be formed which ultimately dis- charge into the sea; and the sands which are washed down by flood waters are deposited in part along the course of such streams, to be carried along again when other rains come, until finally they are swept out to the ocean, whei-e they are deposited as deltas or carried along the seashore, to be built up in banks against the land or to be formed into fringing islands.

Floods. — Stream channels are tlie aqueducts by which th<^ water not evaporated runs off. The streams cut their own chan- nels. Where there is more water to be carried, the channel is made deeper or wider (one or ])oth), and for this pvu'pose there is more water to do the work. But the channels will not hold all the water of great rainstorms : hence floods come, for a flood is the flow of a stream over the banks of its channel. If a stream cuts its own channel, and if the greatei- the amount of water the greater the size of the channel, other things being equal, why is it that floods come f This question must be answered by ex- plaining the manner in which stream channels are choked. There are many minor ways by which they are obstructed, but most of these may be neglected, as they are of small importance; l)ut the two principal methods require attention.

8 PHYSIOGRAPHIC PEOCESSES.

By the first method, a small stream chokes a lai'ger one ; and by the second method, a stream chokes itself. Let us understand the first one.

Consider a stream without tributaries. Suppose that all the water carried by it is derived from one source, some mammoth spring with a constant fsupply, and that no water is added to its volume on its way to the sea. Under such circumstances, the stream cuts its own channel from source to outlet large enough to carry the volume of water, and it never overflows its bank. Now suppose another stream is tm-ned into it, and that this trib- utary drains a region of country where thei'e are intermittent rains. When the rains come, the new stream has a large volume of water loaded with mud washed from the hills and valleys, where the rains are caught which supply its volume. When the muddy stream enters the river, the sands and gi-avels are in jtart deposited below the junction. This forms a dam or obstruction, and tends to cause a flood in the main stream above the junction. Let other streams be turned into the main river ; and wherever such a lateral stream comes in, a dam is constructed beloAv the junction. Now, the river has a series of dams constructed along its course, each one of which tends to cause the river to overflow its banks. The dams constructed in this manner are washed out and built again, and washed out and Ijuilt again, from time to time. Sometimes a series of these dams has been constructed just before some great rainfall, so that the stream is in no condi- tion to carry the greater supply; and a flood results. It is in this manner that large streams are choked by smaller ones, and that floods arise therefrom.

Now, it must be understood how streams choke themselves. '^\nieu the waters are low in any stream, they are clear. When the waters are high, they are muddy, for the rains which cause the increase of voluiue wash the surface soil into the streams. Rain thus makes the river muddy. The mud lirought into the stream, being heavier than the water, sinks to the bottom. Where the waters are SAvift, but little nuul falls ; where the waters are quiet, much mud falls. The waters are swifter around the outside of a bend, and slower on the inside of it. From this slower water the mud is deposited, so the bank of the inner curve grows. As the bank grows, the water is piished over against the other bank on the outer side of the curve, where its flow is increased in velocity so as to cut the bank, and load more material upon the

'I

THE ROCK ENVELOPE. 9

stream. The new load is in part thrown down again at the next bend on the opposite side, where the water is comparatively still. The first curve increases itself Ijy building up on the inside, and cutting down on the outside. In the same manner the second curve is increased in the opposite direction by building up on one side, and cutting down on the other. So it is that rivers not only cut their own channels, but change then- own courses from time to time. In this change the stream is constantly depositing new obstructions, forming dams, which are known as bars; so that, when some great rainstorm comes after such obstractious Ikia'c been built, the water cannot be carried away by the channel, and it overflows its banks, and there is a gi'eat flood.

So one stream obstructs anothei-, and a stream obstructs itself. All floods are ultimately caused by obstruction, and obstructions are chiefly caused by one or both of the methods described.

Thus far we have considered the regimen of streams in a state of nature. Wlien man comes with tlie arts of civilization to change the surface of the earth, additional disturbing factors enter into the problem. Man i)lows the fields, and the side streams carry additional amounts of detritus, and the obsti'uctiiig dams are multiplied and enlarged ; he changes the courses of the smaller streams, and thus introduces disturbing elements into the larger. For the purpose of obtaining water powers, he builds dams, and again changes and introduces new elements into the regimen. Many of the things tliat man does upon the surface of the earth have an influence upon the ruu-ofl!, and generally in- crease the violence of floods; l)ut in lands where ii'i'igation is practiced the waters are taken away from their natural channels and spread over the soils, to be reevaporated into the heavens ; and thus the streams are made smaller, and the floods are dimin- ished or entirely prevented.

THE KOCK ENVELOPE.

The crust of the earth is changeable in a variety of ways : — First, It rises and sinks very slowly, so that usually the changes cannot be perceived, except by comparing some level of land with the level of the sea at long intervals of time ; as tlie hour hand of the clock is not seen to move, but known to move only by intervals of change from houi- to hour. But there may be a time when this change is at once apparent ; that is, wlien a

10 PHYSIOGRAPHIC PKOCESSES.

fissure is formed in the stouy crust, on one side of whicli the laud drops, or ou the other is uplifted, or perhaps the one is dowuthro\vu aud the other uplifted at the same time. The tremor formed from such a movement may be felt as an earth- quake over thousands of square mUes.

Second, When such rents are formed in the crust of the earth, molten matter is often ejected which poxu-s out in great streams. In this manner floods of lava are spi-ead over the sm-face, which, on cooling, become great beds of rock.

Third, ^Mjeu the rains come, and the storms beat upon the mountains and hills, their sands are washed into the streams, and by them are carried awaj\ The materials brought down by the streams from valleys, hills, plains, plateaus, and mountains, are discharged as sands aud clays into the lakes and seas, where they sink. In this manner, by rains and rivers, the lands are carried away, and new lands are formed along the shores of lakes aud seas.

Seas have their tides and waves, and the lakes their waves, which beat against the shores, and undermine the banks and cliffs, and spread bowlders, gravels, sands, and clays along the margin of the waters ; and all these materials are gradually car- ried out by the undertow to a distance from the land. At the same time the materials brought down with the streams are car- ried by currents, and, as they sink, they are commingled with the detritus formed by waves. In this manner lakes are slowly filled, and the seas are ever accumulating new materials upon their shores and on their bottoms.

So there are three methods by which the rocks change their positions. The first is by displacement, when some portion of the crust is upheaved or dropped d(iwn; the second is by volcanic action, when rocks are poured from the interior of the earth as lava, or hurled out by explosions as cinders and dust ; and the third is by transportation, when rock materials are carried from one place to another by streams, waves, and winds.

The three methods of change in the stony crust have interest- ing relations to one another. As the land is upheaved, it is more exposed to rains and rivers ; and the highm- it is carried, the more rapidly is it worn doAvn or degraded by these aqueous agencies. By this process of degi-adation the cnist or rock envelope is weak- ened more and more, and still rises to be attacked l)y the waters. Tims more fissures are formed, more earthquakes occur, aud

KINDS OF ROCK. 11

through the fissures come more and more bodies of lava, cinders, and ashes. The process of degradation by water seems thus to I faciUtate the process of upheaval and the process of eruption. But a time comes when such upheaval and degradation are checked, for reasons not fully known to the geologist ; and slowly through the years, and still more slowly through the centm-ies, and very slowly through centuries of centuries, the upheaval is brought to an end, and the mountains and hills are then ever more slowly degraded until they are brought to the level of the sea.

As the land is upheaved, the sea margin receiving the detritus is thus loaded, and this load jjresses it down more and more, until at last the process of siuking ceases slowly with the glower upheaval of the land.

Why this process of sinking ceases, like the process of up- heaval, is not clearly known ; but the fact that such changes do cease is well known.

It was shown above how rising areas of laud Ijecome rising areas of volcanic activity ; it should also be stated that the sink- ing areas on the margin of the sea, where the sands are deposited, sometimes break as they go down, and fissures are formed through which lava, scoria, and ashes poiu- forth : so that there are land areas of volcanic activity and ocean areas of volcanic activity.

Then, again, lands which have ceased to rise, and have been degraded to the level of the sea, often become areas of depres- sion, and go down below the level of the sea ; while old sea bot- toms that have ceased to sink appear slowly above the surface of the water and become dry-land areas, and in turn are elevated into plains, plateaus, and mountains, where fissures ai"e formed, and volcanoes are built, and rains and rivers carve out valleys and leave hills and mountains. So land areas lieeome sea areas, and sea areas become land areas, until the processes are once more reversed.

Kinds of Rock. — It has alreadj' been seen how fissures are formed in the rock envelope, and how vents are produced which become chimueys, throiTgh which molten matter is poured out upon the surface, and piled uji from time to time by many floods, until volcanic mountains are produced whose chimneys open to the sky in gi-eat funnel-shaped craters. Thus a volcanic mountain is composed of many sheets of lava that have been poui'ed out from time to time through its histoiy. Rome volcanoes are still active, b^^t many have ceased to emit their floods of fire, and dead

V2 PHYSIOGRAPHIC PROCESSES.

voleauoes iu vast numbers are scattered over various portions of the globe.

Volcanoes do not always emit floods of molten rock: they sometimes explode, and throw dust, ashes, and scoria high into the air, which, faUiug to the earth, are piled up iu formations of ti((f'. The very tine dust is sometimes drifted by the winds over great regions of country for himdreds or even thousands of miles; but the coarser materials soon fall, and by a long succession of such explosions mountains of ashes and cinders may be formed. In volcanic regions, cones of such cinders are common. Some- times they attain great size, so as to be several hundi-ed feet liigli ; and they are usually characterized by distinct craters.

Rocks formed of lava and accumiUations of ashes a-ud scoria are called iyncoiis rocks.

Many rocks are soluble, so that the rains, streams, and waves dissolve them. This soluble material is chiefly carried into the sea, where it is deposited by various agencies. The saltuess of the- sea is caused by salt which is washed out of the land and cariied into it. The suspended material is carried into lakes and into the sea. Thus the waters grind down the lands, and bear them away to be deposited under the lake and ocean. The materials are arranged iu layers, thin in some places, thick in others. Very fine materials make thin layers, coarser materials make thicker layers, all of which are called strata. Now, these strata differ in constitution iu many ways, because they come from different streams, which collect sands and clays from different regions of coimtry, and because the waves that tear down the shores find different materials iu different regions. Then all this material brought down to the mouths of rivers and into the surf is assorted : the coarser material soon drops, the finer mate- rial is carried farther, and the rock material held in solution is spread all over the sea. The dissolved materials thus spread far and wide form limestone chiefl}', the very fine nuiterials form day, coarser materials form sandstone, and very coarse matei-ials of gravels and bowlders form conglomerate.

j Many animals live in the lakes and seas ; and when they die, ' their bones are deposited in the forming strata. !Many plants live on the shores and in the waters ; and their leaves and stems sink into the mud, to leave their impressions, and sometimes their tissues, in the forming rocks. Plants and animals live on the land, whose hard parts are washed down by the streams, to be

SEDIMENTARY ROCKS. 13

bui'ied ill the waters, and leave their remains in the rocks. Even the bones of the birds of the air are buried in this manner. All such fragments of life entombed in the rocks arc known na fos- sils. Above the marshes and shallow waters of lake and sea there is a rank gi'owth of vegetation, which falls after matiu'ing from year to year, aii<I is overwhelmed by the waters. As the years go by, generation after generation of plants live, die, and sink below the waters, until great accumulations of such vege- table matter are formed, constituting jwaf. ^Vlien afterward this peat is l)uried l)y sands and clays and gravels, it is slowly transformed into coal, and thus originate the coal beds found in the rocks. The leaves in these rocks afterward tell the stoiy of the life which existed at the time the rocks were formed.

All of these beds of limestone, clay, sandstone, and conglom- erate, are laid down in nearly horizontal strata when first de- posited, or they incline very gently away from the shores. As strata are accumulated in the l)0(lies of water in the manner above descril^ed, one sti-atum is jiiled on another until a numlter are formed, so that they accumulate in tens, hundreds, and thou- sands of feet. In some places they have accumulated to a thick- ness of more than fifty thousand feet, but such great accumula- tions are rare. Accumulations of ten or twenty thousand feet are quite common. As the strata pile up in this manner, the lower members ai-e hardened or indurated.

We have thus found two kinds of rocks, — igneous rocks, which have, been poui'ed from the interior of the earth or blo\vn out by explosive forces; and sedimenfdri/ rocks, which have been deposited in lakes and seas. A third class must be recognized, which is very abundant over the sui'face of the earth, and out of which the soils are made. The hard rocks below are dis- integrated by atmospheric agencies, broken up by heating and cooling, dissolved to some extent by the waters, and disin- tegrated and changed in various ways by chemical agencies. This disintegrated material is washed down by the rains, and gathered by the rills, brooks, creeks, and rivers. Much more is washed down by the rills than is carried by the brooks, much more is carried by the brooks than is carried by the creeks, and much more by the creeks than by the rivers. So the disintegrated rocks are strewn from liiglier to lower lands, and Ijiled up in this manner as bowlders and angular fragments, and as sands and clays, all commingled in many ways ; so that the

14 PHYSIOGRAPHIC PROCESSES.

lowlands have a gi'eat overplacemeut of these rock materials, which are not eousolidated like the rocks deposited uuder the waters, but lie ou the surface of the laud as comparatively loose material. The larger streams, as creeks aud rivers, have low valleys called j>/fl/«s. These streams have theu* chauuels more thau filled by great raius, aud the floods stretch over the ad- jaoeut lauds. AVherever these floods reach, a plaiu is formed, kuown as a flood plain, which is built up here aud there, aud broken dowu agaiu here aud there ; so that the overplaeed uia- terials brought dowu by the floods, aud deposited outside of the chauuel, are coustautly chaugiug from j)oiut to poiut.

The sands that are formed by the disiutegi'atiou of the rocks over the surface of the laud, aud by the beating of the waves agaiust the shore, are drifted by the winds. When the tides of the sea ebb, gi'eat stretches of naked sand are left bare ; and the winds drift the sands alongshore out to sea, aud far back over the laud, sometimes in gi-eat hills and ridges. The sands of the dry laud of arid regions are drifted in this manner, aud are often l)iled into hills aud ridges, which slowly travel before prevailing winds. Such moving hills are known as dunes.

Ice is accumulated ou high mouutaius and in high latitudes, and it moves down the slopes and along the gorges and vallej's, plowing its way over rocks, and carrying into its body sands and bowlders. Thus loaded, it becomes an agency of corrasion, and excavates the valleys and polishes the hillsides, until it reaches a region so low that the ice melts, ami the detritus which it carries is thro^vn down in irregular ridges and piles, fi>rmiug moraines.

All of these materials may be called tnanfle rocks or super- ficial deposits. They are still called rocks, though rarely con- solidated into hard beds. They are the rocks distributed by gi-adation over the land as distinguished from the sedimentary rocks that are deposited on the bottoms of seas and lakes. Thus there are two great classes of rocks due to gradation, — sedimen- tary aud mantle rocks.

Plauts grow on the mantle, which is scattered over all the land ; and as they gi'ow they die and decay aud stain it black at the surface, or tliev are burned and their ashes discolor the rocks. This staiued mantle rock is called soil.

And still a fourth class of rocks must be recognized. "We have seen how rocks are upheaved and thrown dowu by causes not yet fully understood. In this manner great regions are uplifted above

STRUCTURE OF THE ROCK ENVELOPE. 15

the sea-level, aud other regions are displaced, so that the sea flows over them. Then we have seen how the interior rocks are poured out as molten lava. By boring into the rooks, and by deep mining, it is found that the temperature of the rock crast increases from the surface downward at about the rate of 1° Fahrenheit to every fifty or seventy-five feet, as this increase of. temperature is somewhat variable. Now, when rocks are doei)ly buried, they are subject to great pressure from the overlying strata, aud they are greatly heated at depths of many thousand feet. They are also broken, flexed, contorted, aud twisted as the land goes up and down ; and by all these processes sedimentary rocks and igneous rocks alike are changed in both chemical and crystalline struc- ture. The gi-ains of sedimentary rocks are obscured, or often entirely changed into crystals; and the volcanic rocks which have one crystalline form when they cool, have anotlier ciystalline form after they have been changed by this method. All sucli rocks are known as ntctdinurphir.

We must therefore recognize four great i-lasses of I'ocks, — volcanic or igneous jocks, sedhnentari/ ,ov clastic rocks, mantle or superficial rocks, and »u'fa»iorp]tic or changed rocks/

Structure of the Rock Envelope. — The upheaval and sub- sidence of the rock enveloi)e is very irregular in time, in place, and in manner. Some regions of country have been subject through long geological ages to alternate upheaval and subsi- dence on a great scale, so that the total upheaval may be many thousands of feet, while the movements of subsidence may be many thousands of feet. There are other regions where such movements are better measured by hundreds of feet, and still others by scores of feet.

All of these movements are very slow, occurring through thou- sands of years. In some regions the process is gradual, so that the roctks are flexed; in other regions the process is intermittent, the rocks seeming graduallj^ through long centuries to accumulate a strain, nntil at last they yield by rupture, and rise or fall ahnig the rupture pianos; then the strata of one sidi^ lie higher than those of the other. Displacements of this kind are known as/aults. Thus there is displacement by flexure, and displacement by faiilt- ing. Faulting displacement seems always to canse earth(|uakes. : Displacement by faulting seems to be more common than displace- ment by flexing, at least so far as the world has been studied by geologists. In gi*eat displacement by faulting and flexing, regions

16

PHYSIOGRAPHIC PEOCESSES.

of rock are separated into bloeks which greatly vary in size aud shape from district to district. As the beds are hvid down by the water, or jjoured out by erui)tion from the interior, they are formed in layers — some very thin, like leaves of paper; others thicker — imtil some are gi'eat beds tens of feet in thickness. The bods thus laid down are broken by displacement into small blocks by transverse fractures, antl are said to be jointed. There are great regions where such joints are abundant, with rocks broken into blocks only a few inches square, while elsewhere they may be in large blocks many yards square. So far as it is known, the entire rock envelope is broken into small blocks in this manner.

It has been shown that most rocks are oritjinallv forined as horizontal beds ; Imt by displacement through upheaval aud sub- sidence, when the rocks are faulted or flexed, these horizontal beds are tilted in great regional Ijlocks hundreds or thousands of square miles in extent, so that in many regions we find the beds of rock inclined, and they are said to dip in the dii-ection in which they are turned down. In many places the blocks are gently inclined in this manner ; but in many others the inclina- tion is great, aud the rocks are found to be dipping at an angle of more than 45° ; while in many other cases the strata of the blocks stand on their edges, and the dip is vertical ; and yet more, in i-arer cases the lilocks are overturned in such a manner, that the first-formed rocks lie on top, that is, the blocks have been turned more than 90°.

A region of country composed of blocks diiiping in various directions, and at different angles, may be washed down to the

^^mm^^^^^

^^ik

''WWmmmm^

Dia^'i-am of Viu'nnfoviiialile Strata.

level of the sea, and then may slowly sink beneath the sea, and become a region of sedimentation, where rocks are once more accumulated. These new rocks are laid down in IxhIs which are

OMGIN OF OEE DEPOSITS.

17

practically horizontal, upon a floor of beds which are dipping in various directions and at various angles. In tliis manner the newly formed beds will not oonforiu with the earlier strata: that is what the geolouist calls uiiconformit[i.

Uneonfonuitv as seeu in Natvire.

To understand unconformity, put a dozen or twenty thin books on your table side by side, with the backs uj^permost; then place other books on the top of these, the top books with their flat sides next to the edges or backs of the fii-st series ; con- sider the books on edge as a series of rocks dipping at an angle of 90°, and the books on top as a series of rocks lying horizontal on the upturned edges of the lower rocks. You will tlien under- stand what the geologist means when he says that he has dis- covered two series of rocks, one of which is unconformable to the other. It is not necessary that the first books should stand on edge (they may incline at any angle); but if the upper rocks have one inclination, and the lower rocks anothei-, there is said to be an unconformity. It will be seen that sucli an xmconform- ity has gi-eat significance in geologic history. The rocks below were formed at one time, and the rocks above at another and later time ; but these times were separated by a dry-land jjci-iod of upheaval and degradation which may have been very long.

Ores. — Now, the rocks, as they are laid down by water and

poured out from the interior of the earth, contain iron and nianj^

i other metals. As the waters percolate down the fissures, they

dissolve the metals and other substances, and redeposit them in

18 PHYSIOGRAPHIC PROCESSES.

the fissures as ores. Sometimes these fissures come to be veiy wide, — many inches or even many feet across, — but as they open, they are tilled with ores by the percolating waters. Usually the fissures do not open completely by one movement, but open gi-adually from time to time ; and when they thus open, they are displaced, that is, there is a vertical movement along the plane of fracture. There are thus two irregular walls ; and as the move- ment goes on, the projections in these walls hold them apart, and the width of the fissures increases with the depth of the displace- ment. With every change occurring in this manner the fissure increases its width, and new deposits of ore are formed to fill the vacant spaces. Thus the ores often have a lamellar or leaf struc- tiu'e corresponding more or less Avith the walls of the fissure.

Such fissures and displacements occur more abundantly in regions of volcanic activity, where the waters are heated by the hot rocks, and their chemical activity increased by the higher tem- perature. This action of hot waters is known as solfataric action, and solfataric waters are quite common in volcanic regions.

Many of the rocks, especially limestones, are highlj' soluble, and such may be placed between beds of insoluble rocks. Under these circumstances, where conditions are favorable, the soluble rocks wiU be carried away by percolating solvent waters : and as fast as they are removed, they may be replaced by various ores. Siich ore beds are common, and often of great value by reason of the great quantities of ores derived from them.

Again, ore deposits are often found in unconformities. Iron is often deijosited as a bog ore in unconformities. Such ores may ultimately be covered by sedimentary rocks. Again, in such unconformities percolating waters carry away the soluble materials, and leave behind the ores of metals ; so that deposits of ores are common in unconformities. As the subject of ore deposits is one of gi'eat magnitude, it is not uecessaiy that it should receive full treatment in this place ; but what has l:)een said may be summed uj? in the statement that ores are found in great abundance in veins formed in fissures, that they are formed in beds where they have replaced soluble rocks, and that they are discovered in gi'eat unconformities.

Age of Rocks. — From the pre\-ious explanations of the re- gion it will be clear to the student that rocks may be of diflferent ages, — that some were f onned a very long time ago, some but lately, and others are forming now. One of the great subjects

AGE OF KOCKS. 19

of iuvestigatiou that geologists imdertake is that of determiuiug the age of the rocks. This research has beeu carried on iu many lands by many men, so that much is known about the age I of rocks. The oldest rocks are known to be many millions of years old, but how many millions cannot yet Ije decided. From the formation of the oldest rocks to the present, the time is very long. This time has Ijeen divided by geologists into periofls, and the periods again subdivided; ))ut for the present pm'pose it is only necessary to consider the grand periods into which geologic time is divided.

1 The oldest rocks known are called Anlican. In them no 'fossils are found. The period of their deposition is called the Arcliean period.

The next period in succession is called AJfioiihiioi. \^\ the rocks formed during this age no well-defined fossil forms have been found, and yet there are evidences that life existed.

Following the Algonkian i)eriod is the Carnhndu, in which fossils are found with well-defined forms ; but tliey all prove to be- remains of animals of very simple and low structure.

Then follows the Silurian period. The rocks formed in Silu- rian time contain many nioi-c kinds of fossils than the rocks of Cambrian time; and their remains show that these animals were some of them of low structure, as in Cambrian time, but that others were of much higher forms.

Then follows the Dcroiiiuit, period, with a still ginuiter number of kinds, and among them still higher forms.

Then follows the Carhoniferous period, with evidences of plant and animal life still more varied, witli forms still moi'e highly developed.

Then succeeds Wn'. Jiinitiidti jH'i'iod, with life forms still more highly developed.

Then follows the Crcfdceous period, with more liighlv evolved life.

Then follows the J£ocene period, with yet more highly evolved life.

Then the Neocene period, with fossU life more varied and more developed tlian ever before.

Finally wo reach the rieisfoeeiic period, which includes tlie present time. In this period the mantle rocks have ln'cu formed, while lake and ocean deposits have been made during the same time.

20 PHYSIOGRAPHIC PROCESSES.

Tims we liave the following table of periods, the last period at the top of the column : —

Pleistocene,

Neocene,

Eocene,

Cretaceous,

Juratrias,

Carboniferous,

Devonian,

Silurian,

Cambrian,

Algonkiau,

Archean.

From Land to Sea, and Sea to Land. — Displacement by faulting and flexing plays a very important part in determining the ]ihysioal characteristics of the land. If there were no uji- heaval, the rains and streams would degrade all the lands to the level of the sea, and all islands and continents would become vast marshes. But for displacement, there would be no volcanic or exjilosive eruption : so even the volcanic mountains would disappear. By displacement deep basins are formed in the rock envelope which holds the seas and great lakes, while, at tlie same time dry lauds are formed. But these di-y lauds are l>roken with faults into great blocks hundreds and thousands of sqiiare miles in extent, and are tilted in various dii-ections ; other regions are flexed or bent into great wrinkles ; and still other I'e- gions are in part faulted, and in part flexed. All dry lands are brought above the level of the sea by displacement and igneous action ; and as soon as they become dry lands, the rains fall upon them, and carry them away. It is thus that the lands are pri- marily due to upheaval and igneous action. Then their surfaces are modeled by rains and streams, which are the great sculptors, candng valleys, and embossing the hills and mountains.

The altitude of the region of country above the level of the sea is the difference between the amount of upheaval and the amount of degi-adation liy the waters. The upheaval may h-ave been hundreds or thousands of feet, whili^ the degradation is always less if dry land remains. The upheaval is always an irregular warping, with flexures and faults on a grand scale ; the degi-adation is always an irregular car-ving by rains, liUs,

EXPOSUKE OF OLDER 'kOCKS. 21

brooks, creeks, and rivers, aided by the beating of the waves against the shores. Where the rivers run, the degradation is rapid, for the great streams carve deep and wide cliannels; and these channels are narrower and more sliallow wliere the trib- utary streams come down, the channels becoming less and less as the streams divide again and again, until they disappear in liillside rills. The upheaval of the land by displacement, and the Ijuilding of the land ))y volcanic activity, are the methods l)y which the lands are brought above the level of the sea ; and the carving of these dry lands by water is the method by which physiographic features are produced.

Man is enabled to study rocks as they are exhibited in stream banks, in the quarries of hillsides, in the faces of cliffs, in wells and in deep mines. In this manner he is enabled to see something more than the alluvial rocks at the sui'faco. The deepest borings and mines are rai'cly more than a tVnv liuiidred feet, though there is an occasional mine or boring which reaches down for a few thousand feet. Then we can study I'ocks which come from below through volcanic vents. But the geologist may study rocks that have at one time been very deep in the crust, and have since been upheaved, and the overlying rocks carried away by water; so that it is not uncommon for the geologist to see rocks which he knows have been buiied in former times to a depth of thousands of feet, and he is sometimes abh^ to exam- ine rocks which he knows were originally deposited from forty to sixty thousand feet below their present altitude. It is by all these conditions that the structure of the rock envelope is re- vealed.

In a great mountain range the crust may have been wrinkled in one great flexure extending along a line hundreds of miles in length, the flexure spreading from the central line of u]iheaval for tens of miles. This great i)lain may have been ui>lifted in its central portion forty thousand feet or more, while the rains may have carried away from the crest perhaps thirty thousand feet or more of the rocks. So, in passing from the foot of the mountain up toward its crest, the geologist walks over the upturned edges of the strata, and studies them in succession, and measures their thickness, and collects from them the fossils which they contain, from bed to bed, as he goes uji the mountain geograi>hically, but flnds rocks that contain forms of lower life. As he changes his view from the later-formed strata in the valleys to the earlier-

22 PHYSIOGRAPHIC PKOCESSES.

formed strata at the mountain summit, he roAiews the history of the plants and animals that succeeded from a primeval life to the life of the present time.

It is thus that the geologist is enabled to review in one day's walk a panorama of the history of millions of years. As he walks, he may pass over beds of ancient shells, and find the bones of ancient animals, and discover the site of ancient coral reefs, and tread on the rocks of ancient shores, and find the plants of ancient forests, and at the same time gaze on canyons carved by mighty rivers, OA'erlook valleys carved by glaciers, and watch the clouds play among the cirques and pinnacles of towering mountains.

IN'TERPENETKATION OF THE ENVELOPES.

The envelopes of air, water, and rock are so distinct that they can be clearly distinguished; and yet, when they are carefully studied, it is discovered that every one encroaches upon the ter- ritory of the others, not only by interaction, but also by inter- penetration. It has already been shown that the water pene- trates deep into the rock. Every sjiriug that falls from a hillside gives proof that the rocks above its level hold water, which they j'ield slowly as a perennial supply; and the innumerable hills of the continents and islands have their innumerable springs. Everj- well proves that there is water below; every artesian fountain shows the existence of undergi-ouud waters; and every boring in the crust of the earth, and every excavation in uudergi-ound min- ing, discovers the jiresence of water.

Wherever water flows, air flows with it, and all natural waters are permeated with air.

The aqueous envelope is everywhere permeated with rock, which it holds in solution or suspension, and there is no natural water absolutely jnu'e. The sea is full of salt. Halt lakes are more than full of salt, and so they must throw it upon the bottom ; and the waters hold lime and many other sulistances. Not a drop of pure water can be found in the sea; not a drop can be found in a lake ; not a di'op of pm*e water can be found in any river, creek, brook, or spring; and not a drop of pure water can be found >un- dergi-ound : it is all mixed to some degree with rock.

All natural waters are aerated. No drop of water unmixed with rock and air can be found, except by the process of artificial purification.

\

VULCANISM, DIASTROPHISM, AND GRADATION. 23

But surely there is pure ah- ? Nay, not so. There is no natu- ral air unmixed with rock and water. All the air which circu- lates above the laud and sea, within the ken of man, and all the air which circulates underground, is mixed with rock and water.

Pure air is invisible : it will not reflect light ; it is transparent, but will not convey light. Light is conveyed through the atmos- phere by ether, and is reflected and refracted by rock and water; and it seems to be largely affected in this manner by rock. If the ambient air of the earth were pure, there Avould be no color in the sky, no rainbow in the heavens, no gi'ay, no purjile, no crimson, no gold, in the clouds. AU these are due largely to the dust in the air. The purple cloud is painted with dust, and the sapphire sky is adamant on wings.

Land plants live on undergi-ound waters : were there no sul)- terranean circulation of water, there would be no land plants. Fishes live on under-water au- : were there no cu-culation of sub- aqueous air, there would be no fishes in the sea. The clouds are formed by particles of dust in the air, which gather the vapor : were there no dust in the air, there would be no clouds ; were there no clouds, there would be no rain.

VULCANISM, DIASTROPHISM, AND GRADATION.

From what has hitherto been said, it will be jilain to the reader that there are two grand physiographic changes by which the forms or f eatm-es of the land surfaces of the earth are produced, — one by which the land goes up and down, that is, by vei'tical change; and the other by which the land is transported from one district to another, that is, by horizontal change.

The vertical changes are produced by two processes. By one, materials from the interior of the earth are bi-ought uji to its surface. This may be called rnlcanisin, and we liave volcanic pro- cesses. By the other, regions sink, and regions rise, and the up- heaval and subsidence may be called diasfrophisni, and we liave diastrophic processes. The horizontal movements consist in the transportation of materials from one region to another, generally by the agency of water, but to some slight extent by the agency of wind, and to a very slight extent by the agency of life, for the animals build up materials of the earth into their tissues, and transport them from place to place ; but for our piu'pose we may neglect life agency and wind agency, and consider only the aque-

24 PHYSIOGRAPHIC PROCESSES.

ous agency. By aqueous ageucy the rocks are degraded from one region and transported to another, and there built up or constructed into new forms. This may be called fjradation, and we have grading processes. Hence we have to consider vol- canic processes, diastrophic processes, and grading processes.

VuLCANiSM. — By volcanic processes materials are brought from a gi'eat depth to the surface, when they are said to be cr- trmled; and sometimes they are brought from great depths and left still within the crust, filling crevices, or pushed laterally be- tween layers of the crust: then the lavas are said to be lutrnded. Of that which comes to the surface, a large part is in a molten or fluid form ; but another almost as large part comes out as frag- ments thrown up by explosions. The lavas that are poured out form coulees, or sheets of rock, when they are cooled, and often one is piled on another; and sometimes vents are produced which are kept open for a long time, or periodically are closed, so that there may be a continuous or an intermittent pouring of lava. Sometimes the melted lava is sent to the smi'ace and high into the air by explosive action : cinders are therefore lavas that have been extruded l)y explosion while yet molten.

Some lavas extruded by explosion come out in the form of fine dust, as if the explosive agency had thoroughly pei'meated the lava itself ; and when the explosion comes, it is torn into the most minute fragments, constituting an impalpable ash. Be- tween dnst or ash, cinders or scoriae, and sheets of lava or coulees, no distinct demarcation can be made : they gi'ade into one another. From the finest dust there ai'e gradations into cinders, and from the cinders there are gradations into coulees; and yet the dust is sent into the air as fragments of ash, and the coulees come to the surface in flowing streams.

The coulees, cinders, and ashes come from the interior inter- mittently. In a great region of country, like that of the Eocky Mountains or of the Andes, an eruption occurs at one time and then at another, and at one place and then at another. Usually the irregularity of place is very great; so that large areas of coun- try are subject to volcanic activity, and have sheets of lava spread over them — now here, now there — from time to time. But oc- casionally the eruption is concentrated for a long time at one point, so that eruption follows eruption from one vent, and then volcanoes are produced; but the more common process forms only volcanic plateaus of very irregular outline. Enough, per-

DIASTROPHISM.

25

A ( Viuleu (if Liiva.

haps, has been said to make it i^lcar liow the hind is l)iiilt uj) by vulcauism.

DiASTEOPHlSM. — This is the uplifting and subsidence of the earth's crust. Why the rot^k env(^lope, wliich must bo of onor- mous weight, is really moved in this manner, is not ■well known ; or, at any rate, no scientific man has explained it in such a man- ner that all other scientific men agree with him. To the fact of uplifting and subsidence all agree, and to many of its character- istics there is general assent ; but no complete explanation of this cause has universal acceptation. We are therefore under the necessity of stating some of tlie facts of displacement with-

26

PHYSIOGRAPHIC PROCESSES.

i

out properly showing theii' causes. It is well known that the rocks are fractiu-ed 1 )y iri-eat fissures miles in length, or scores of miles in length, or even hundreds of miles in length, and that along these fissures the rocks are displaced. Sometimes the rocks go down or up on one side, and it seems that there are times when the rocks go down on one side and up on the other at the same time, and this may always be the ease. "When rocks are displaced in this manner, they ai-e said to hefaiilfed. Small faults and great faults are found in the rocks. The amount of dis]tlacement is called the ihroic; and the throw may be just perceptible, or it may be thousands of feet. In some cases the faults may be but a few yards in length ; in other cases they may be hundreds of miles. Great faults are never made at one movement, but by inter- mittent smaU movements following one another in a long succes- sion. Sometimes a fault which is single for a distance will diWde into two or more fracti;res, with two or more displacements; sometimes there is a series of parallel faults, so that the entire disi^lacemeut is produced by a series of steps. As the faulting is intermittent, and as years or centuries, or centuries of centuries, may intervene between movements, great change may be wi'ought in the surface along the faults by rains and rivers cutting out valleys and leaving hills. Then from time to time lavas may pom- out through the fissures, and flow do"mi into the vaUeys between the hills, or may even cover up the hills; and when the faulting is renewed, the lavas themselves are fractured. Sometimes these lavas form obstructions or dams in the valleys.

Diagram of a Fault.

f a Moiioc'liiial Flexure.

and the waters accumulate therein, and sediments are washed into tlu^ waters, and sedimentary rocks are deposited in the lakes over the fissm-es. When the diastrophic activity is renewed, — that is, when the faulting again occurs, — these beds are broken. Regions of country treated in this manner may be again faulted

FAULTS AND FLEXVRES.

27

by parallel fractures, and carved into valleys and hills, and cov- ered with lavas and sedimentaiy rocks, and broken again from time to time. This may go on for millions of years, and for a long distance, say, hundreds of miles. The total effect of such a series of displacements will make the country on one side of the line of faults very much higher than it is on the other ; while the rocks uplifted will be turned up so that they dip away from the faulted zone.

It is thus that we sometimes find a simple fault to be a mere fracture, with a single displacement ; while at other times we find complex fractures, with many displacements, and a long history involved.

;p#^v>--;S*';W" \ J':^'^'9'f^^gm'?>li»'^i^"7^':

^'

A Mouocliual Flexiu'e as seen in Natui'e.

The same amount of displacement can occur under very different conditions. Cut a sheet of paper in two, and arrange the parts on your tahle so that one of the cut edges lies higlun* than the other, say, about an inch. Tluni bend another sheet of paper down and out again, so that on one side of the bend the

28 PHYSIOGRAPHIC PROCESSES.

paper is an incli higher than ou the other. By the two methods you luxve made two kinds of displaceiuents, — one by faulting, the other by flexing. Now, rocks on the crust of the earth may be beut iu this manner, and such bends are called iiionocUiidl Jicx- ures. Both forms of displacements are common, but faulting is more often seen than flexing.

A series of parallel monoeliual flexures of this kind, not very far apart, produce a series of wrinkles; and we have upturned wrinkles and dowiitunied wrinkles. The upturned wi'inkles are called a)iticU)i(tI, and the downturned wrinkles tfijiicliiial. Such anticlinals and synclinals are usually called folds, and so we have anticlinal and synclinal folds. Thus displacement is represented by faidts, mouoclinal flexures, and folds. Faults change into monoeliual flexures sometimes abruptly, and sometimes grad- ually,— that is, the tiisplacement may be carried on for a time as a flexure, and suddenly change and become a fault, — so that it is impossible to draw an absolute distinction between faults and mouoclinal flexu.res, and between flexures and folds : one method of displacement ruus into another.

The crust of the earth, or the rock envelope, is of great thick- ness, but just how thick is not known, probably several miles ; and these faults, flexures, and folds are found to extend as far down as man is able to study the condition of the rocks. It seems probable that great faults extend quite through what is known to geologists as the crust, and there is some e^ddence to show that often that which appears as a fault at the surface, ap- pears as a flexure at a gi'eat depth ; but this is a generalization which must be made with some reservation, because observations have not been can-ied to such an extent as to warrant the state- ment that si;ch is tlie law.

By gi-eat faults and flexures the crust of the earth, so far as it is known to man, is divided into great regions scores or even hundreds of square miles in extent ; but each of these parts is again broken by smaller fractures called joints. Sometimes this shattering is very minute, sometimes it is very coarse ; but it is usuallj^ more or less regular, so that the blocks are broken into somewhat regular forms. Thus it is that the wovkuuiu in quarrying rocks never finds them in continuous bodies, but always discovers that they are broken into blocks of greater or less extent.

Perhaps we have i^resented already all that is necessary on

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29

30 PHTSIOGR-U'HIC PKOCESSES.

the subject of diastropliism for the purpose uuder eousideratiou ; namely, to exphiiu the origin and characteristics of the surface featiu'es on the earth.

Gradation. — This process is accomplislied through the ageuey of water. First, the rocks must be disintegrated; second, the rocks must be transported ; and, third, tlie rocks must be depos- ited. Thus we have di.sititcf/rutioii, iraiispoiiuti<»i^ and deposi- tion. Rocks are disintegi-ated by chemical action, with expansion and contraction by changes of temperatm-e. Rocks are disin- tegrated mechanically chiefly by the abrasion of streams and glaciers. Then rocks are undermined and broken down by gravity in the banks of streams, and in cliffs that are formed in various ways.

The material transported l)y water must be loaded, and it is loaded by being driven by rains and streams from higher to lower position and by the undermining of banks. The load is heavier than the water, and hence it sinks. The finer the mate- rial, the longer and farther it will be carried by the water, while the very coarse material sinks at once. The swifter the current of the stream, the farther the load wiU be carried. But this is in part counteracted by another condition that springs from the increase of the velocity of the current. As the velocity is in- creased, the depth of the water is diminished, and the load has a less distance to fall in reaching the bottom. In streams much material is diiven along at the bottom as it is rolled over by the force of the cm-rent. As a stream flows, the material carried is thi"own down from time to time, the more as floods subside, and is reloaded from time tt) time, the more as floods arise, until as fine sediment it is carried into the still water of some lake, or into the sea, where it is assorted and arranged by waves and currents, and is mixed with the sands and gravels formed on the surf, and finally consolidated into hard rocks.

The rain and the snow are spread over the surface, and wash it all ; but the nils that come from snow and rain run in little channels, and these rill channels converge into brook channels, and brook channels into creek channels, and creek channels into river channels. We have therefore two ways liy which the Inud is degraded by water, which should ]>e discriminated : the wash of rain and snow we vnll call erosion, and the cutting of channels by streams we will call eorrasion. No perfect separation can be made between these two processes; l)ut yet eorrasion must be

-Alarlilc Ciiiiyoii foi'i I l,y <],,■ ('nii:i«i(ni of i lie Coliirado kivfi-.

32 PHYSIOGRAPHIC PROCESSES.

discriminated from erosion, for by corrasiou deep channels are carved, and some of the most sublime scenery in the world is dependent upon it, for the great cauycnis are carved by cori-asion.

The material transported by streams of ice is loaded in two ways : it falls from overhanging cliffs to the surface of the ice, and it is plucked by the ice from the bottom of the channel. As the ice is divided by cracks and again reunited, some of the sur- face load of the glacier falls to the bottom, where it becomes imbedded, along with the i)lucked fragments, in the lower layers of the ice. Exceptionally, and in ways that are not understood, some of the material escapes from the lower surface of the ice, and forms local deposits over which the ice slides; but in the main all the glacier's load is carried forward to the limit of its motion, where the ice melts, and the load is dropped in an irregular heap called a moraine. Streams of ice, like streams of water, corrade their channels, iising the rock fragments l)edded in their lower parts as cutting tools, and the rock flour thus aliraded becomes part of tlie load to be deposited with the rest in the moraine.

It will be seen that we must distinguish three grand pi'ocesses by which the features of tlie surface of the earth are i>roduced, — nilcaiiisDi, diastrophism, and yradatioii. There are other minor processes; but they are so small compai-ed with these, that for our present purpose they may be neglected. All we have hitherto said has had this result in view, — that we might clearly imder- staud the three great physiographic processes.

We have learned of three great moving envelopes, and of how they are in motion; and in studying this subject we have discovered the three processes by which the features of the earth's surface are molded in such a manner that we have seas, gulfs, bays, straits, lakes, rivers, and fountains, and that we have continents, islands, plains, plateaus, mountains, hills, and valleys. How all of these features are produced, and many others of minor importance, must be the theme of another pajier.

PHYSIOGRAPHIC FEATURES.

By J. W. PowTSLL.

A VOLCANO in actiou is a scene of wondei-. The storm of rock, the luminous vapor, and, more than all, the exhibition of stupendous force, condnne. to make it a sublime spectacle. The method by which a volcano is constructed was explained in a for- mer monograph as a jiart of the great process of vulcaiilsm. In the same monograph the manner in which great blocks of the crust of the earth are upheaved, tilted, flexed, and folded, was sho\\^l, and the process by which this upheaval is carried on was called (Uasfrophism. Diastrophism also has elements of sublimity ; not to untrained sense, but only to instructed reflection, that under- stands the gi-and energies employed and the mighty works done. Again, it was explained that mountains and plains are carved by \ rains and streams, leaving behind plateaus, mountains, hills, and valleys ; and this process was called (iradatloit. The sublimity of the processes of gradation is grasj^ed only by reflection on the energy of the sun in lifting the waters of the sea into the air, and driving them in flocks of clouds over the lan<l, and Inu'ling them in storms to beat the rocks into sands and bear them away to the bosom of the ocean whence the waters were lifted. If these three processes are jiroperly comprehended, then it is possible to understand the origin of the physical filatures of the surface of the earth, such as continents and islands, seas and lakes, to- gether with such forms as plains, plateaus, moiintains, valleys, hills, and many other interesting features.

The ocean covers about three fourths of the surface of the earth; and arms of the sea extend into the land, forming gulfs and bays. Strictly speaking, all lands are islands. The two Americas together constitute an island, and the entire island is sometimes called the Western Continent ; and sometimes North America and South America are each called a continent. Eu-

(Copyright, 1895, by American Book Company.) 33

34 PHYSIOGRAPHIC FEATUEES.

rope, Asia, and Africa together constitute another gi-eat island, the largest of the earth. This island is sometimes called the Eastern Continent ; and sometimes Europe, Asia, and Africa are severally called continents. Australia is another great island, and is sometimes called a continent. In addition to these gi'eat continental islands, there are many smaller islands. All of these islands, continental and minute, — that is, all of the land sur- faces of the earth, — have been sea bottom at some time or other, and the waves of the ocean have rolled over them all ; they have all been brought above the level of the sea, and have all been fashioned into their present forms by the joint action of %Tilcan- ism, diastrophism, and gi'adatioii. The ocean has its shores fretted with many salients, as gulfs and bays, all due to the three gi"eat processes. How the forms of land and water are produced is the story now to be told.

PLAINS .\ND PLATEArS.

Plains. — Whenever in any region the process of slow up- heaval comes to an end, and such district is still subject to degra- dation by rains and streams, the process of reduction goes on until the surface is brought down to the level of the sea or lake into which its waters discharge. At the same time the land may increase in area by the deposit of sediments which have been carried away from its surface and added to its margin : in this manner the low plain is enlarged. A phihi, therefore, may be due in part to degi-adation and in part to sedimentation. By one or both methods all plains are formed. The huse-levd of a plain is the level of the sui'face of the sea, lake, or stream into which the waters of the plain are discharged.

Sea I'lains. — The sea-level plain is permanent in the absence of diastrophism, for it cannot be degraded below the action of waves. It will be understood that the land plain which is brought down to the level of the sea has its margin on the seashore, and that it extends l)ack from the shore a distance which may be miles or hundreds of miles. As it stretches back, its surface rises slightly. The whole plain is not brought down absolutely to the level of the sea, but only nearly to that level, so that the water runs off by slow, deep, meandering streams. The wash of the rain over the surface is comparatively little, and the slow streams are usually clear, or, when turbid, are stained with Itlack soil,

PLAINS. 35

Ijut they do not carry great quantities of mud. Such is the typical plain as it borders the sea. Low lands with sm-faces more inclined, and with more swiftly running streams, are still called plains, though they are not fully brought down to base- level; sometimes they are called 2)cn('2)l(iiii.'i (almost jJains).

Lake Plains. — Other plains may be formed with their base- level depending upon the levels of lakes. Such plains are in the interior of the land, and may be high above the sea. The base-level of a lake is not permanent, like that of the sea, but is changeable. Every fresh-water lake has an outlet or stream by which it overflows the lake barrier. This stream may cut the barrier down ; that is, it may corrade its channel deeper. The deepening of the channel commences Ijelow, away from the lake, and progresses back upstream until the lake is readied. Then the waters of the lake rush througli the newly opened cliannel, and the lake is drained in whole or in part. The plain depend- ing upon such a lake will tln;s have its base-level changed. If a lake is thus partially di'ained, the new dry land stretches back to the old shore line, where bluffs have been formed by the waves. This old shore line with its bluffs is a conspicuous ter- race step to the older and higher plain. A lake may change its level in such manner from time to time, and a series of old shore lines may be left, so that a series of plains will appear separated by low t'errace steps. Terraced plains are often formed about lakes in this manner.

Stream Plains. — A river maybe hunch'eds of miles in length. As it flows along, it passes through rocks of varying degi'ees of hardness. Where the rocks are firm and stable, corrasion of the stream is slow; where the rocks are soft, corrasion is more rapid. In this manner the river is divided into lengths, or reaches. Along its course where the rocks are hard, the stream is narrow and swift, with rapids and faUs; where the rocks are soft, it is wide and quiet. So the river is often a stairway from an ujjper to a lower region. The slow reach is a hase-lerel, like that of a lake, below which the l)anks and hills on either side cannot bo do- graded ; and local plains are thus formed, which rise gently back from the river. These we will call stream plains.

Sometimes another process provides SAvift reaches to rivers: diastrophism is the agent. There may be a slow upheaval of the land athwart the com-se of the stream. As the land rises, the river cuts its channel, so that it still flows on : for the faster

36

PHYSIOGKAPHIC FEATURES.

the land rises, the swifter is the current ; and the swifter the

ciUTent, the more rapidly the rocks are cut away. So the river

jcorrades its way through obstructing rocks as they rise bydias-

Urceii liii\('r ciillin;^^ its * imuiu'l tlirougU llu' i iiiiali MimuiMiii^ .i> iiii_\ il^^c athwart its Course.

trophism. Such an upheaval of rock across the current of a stream may last for a long time, and the river may be held to a base-level for all that time, and extensive plains may be carved.

PLAINS. 37

The preservation of a local base-level of a river iu this manner is common. In the history of a plain thus formed, terracing may occur like that made by the lowering of lakes. This is accom- plished by the cutting away of the swift reaches, which changes the base-level of the slow reach above. So the local plains are sometimes terraced.

Flood Phthis. — In the history of a river a slow reach is soon formed immediately above its mouth, where it enters a lake or the sea, and this slow reach is gradually extended upstream until it is tens or hundreds of miles long. In the jjrocoss of ex- tending the slow reach up-river, the swift reaches iu the hard rock are cut out, so that the river has but a low declivity. The stream cariies sediment, which it deposits just outside its mouth, and thus a delta is foi-med. So the slow reach at tlie mouth of the river is lengthened downstream by the growth of the delta, and' upstream by the coi'rasion of the channel down to the base- level.

River channels are corraded by their own waters, and the streams use the sediments which they contain as the instnnnent of corrasion. As a river cuts its channel down toward the base- level, it has less and less vertical cutting to perform, and then its energies are turned against its banks. The way in which this is done is of gi'eat interest. As the declivity of the stream is less, the water of the stream is retarded in its flow, and the sediment carried in the water is more rapidly deposited Ijccause the waters are more quiet; that is, the distance to which the load is carried is shorter. The swift stream carries its load much farther than the slow stream.

A curved stream has slow reaches and swift reaches. "WHiere the water is slow, bars are formed, for there the load is thrown down ; where the water is swift, the channel is cut, for there the load is an instrument of corrasion. Against the outside bank of curves the river flows with a swift current, and cuts. Along the inside bank the current is slow, and deposits are formed. A deposit formed on the inside bank throws the water still more against the outside bank. Thus, while one bank is built, the other bank is cut ; for on one side the current of the stream is swift, and on the other side the cui-rent is slow. These jjlaces of deposition and lateral corrasion are modified in many ways that need not be considered here.

As a river ceases to corrade vertically, it gradually begins to

STATE NOfiMALSCHOOL

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38

PHYSIOGRAPHIC FEATURES.

Mississippi Kiver. near Greenville, Miss.

coiTade horizontally or laterally. Thus vertical corrasion is turned iiito lateral corrasiou. The banks are cut in one plaoe, and the load is deposited iu bars in another. So banks are built and banks are car- ried away ; and when the stream has practically i-eached its base- level iu the sea or lake into which it discharges, aU its corrasiou is lateral, antl the cut at every out- side bank adds to the instrument of corrasiou,while the bar of every inside bank adds to the force of thewateragainst the opposite side and below, so that the currAit is thrown against the banks more aud more, and loaded more and more, until the rate of lateral cor- rasiou is much greater than was the rate of vertical corrasion.

Kivers subject to lateral coitet siou iu this manner ever change theu' courses, ploA\"iug to the right and plowing to tlie left, sendiug their cm'ves far back toward the hills mitil curve meets curve in its outer limit, aud a cnt-off is pro- duced. A gi-eat river iu a flood plain squirms like a great serx>eut on the desert. "With every fold iu its long form it cuts away new land on oue side, aud builds up new land on the other. So such rivers sway back and forth across their valleys, and dig away the laud on both sides down to the bottom of their channels, always to build it up again. A wide val- ley is carved by the river to the level of its bottom, aud built up

PLATEAUS. 39

again iu a plain to the level of its high water; and this built plain in an excavated valley is known as a. flood plain. Such a flood plain may be formed along any quiet reach of the river from its source to the sea.

So we have sea plains, lake plains, stream plains, and flood plains.

Plateaus. Diastrophlc I'lateaus. — When iu a great district of country the process of upheaval has fairly set in, it may continue for an indefinite time; and the land-formed or sea- formed plain may rise higher and higher as the centuries roll by, until it is lifted hundreds or even thousands of feet above the level of the sea. As it is carried u[) iu this manner, rains fall upon it aud dig it down, and the streams carry the matei'ial away. The principal rivers cut their channels deeper and deeper, the lateral rivers cut their channels deeper and deeper, the creeks cut their channels deeper and deeper, and the rills that run only when the rains fall cut their chainiels deeper and deeper, so that the rising plain is divided by a multitude of large and small streams ; but the summits between the streams remain for a much longer time, and preserve, in a rough way, a general level. The site of the old plain, marked by the hilltops, will long be visible to the skilled eye of a geographer. Wlien a plain has thus been uplifted and carved with stream channels while the hilltops yet renuiin to mark the surface of the old plain, it is called a j)Iaf('ai(. Tluis plains are due to gradation ; plateaus, to diastrophism and grada- i tion. It is manifest that tlie plain thus gi-adiially merges into \ the plateau by process of upheaval and gradation. For tliis reason it is not practicable to clearly discriminate plateaus from plains, and in the common practice of applying names some confusion arises. The same region of country will sometimes be called a plain, and sometimes a plateau; for a plateau is biit an elevated plain, and the degree of elevation and gradation to which it iiuist submit ere its name is changed cannot always be determined with exactness.

A great plain, as it is lifted up, maj'' be broken into parts by another agency; that is, hy fractKring and fault in ff ; and the blocks into which it is thus divided may be variously lifted and tilted. In such cases tlu^ edgi^ of the i)lateau may still be defined as the escarpment of a gi'eat fault. Such displaced blocks are quite common in some parts of the United States. All plateaus that are formed by the upheaval of plains, and ci;t into parts by

40 PHYSIOGKAPHIC FEATUKES.

rivers, or broken into parts by faults, or divided into parts by flexiu'es, Ave will call (riastropJiic -plateaus.

Vulcanic PUdeaiis. — In the study of vulcanism we learned, how volcanoes were formed, and bow coulees of lava were poured* out on the surface of the earth, and how strata of dust and ashes j were spread over the land. Now, di;st and ashes poured o\it in this manner, together with coulees of lava piled up one upon another over a gi'eat region of countiy, may produce a plateau. So we have ritlcfDiic plateaus.

A plateau is only a lifted and rather irregular plain, and a plain is a more regular and less lifted plateau. Should we call them all plains, then we would have plains of gradation or time plains, (Viastrophic plains {diastrophic plateaus), and vulcanic plains {vulcanic plateaus).

MOUNTAIXS.

Vulcanic Mountains. Tush'ar Mountains. — Vulcanic plateaus are common as great elevations of laud composed of coulees, beds of cinders, knd accumulations of ashes. Sometimes small cinder cones are found as weU-developed forms, and old cinder cones appear more or less degraded. As the lavas are poured out ' and piled up, streams cai"ve canyons, gulches, and valleys, which from time to time may be again filled with •vulcanic material from '- below. Finally the "siilcanic action ceases, and such plateaus are i carved into mountains. In the United States the greater number of vulcanic mouiltains are of this character, composed wholly of j vulcanic rocks. More or less modified by diastrophism, they are called tushar mountains.

Volcanoes. — "We have akeady seen how mountains are poui-ed out from the interior of the earth through volcanic vents. Such extravasation is always intermittent. Sheets of lava are poured out, and flow down the sides of the mountain, and build it higher. Then the action ceases for years or centuries, to be renewed from time to time. The years of rest are many more than the years of activity, and in tliem great changes occur. The beds of lava are covered with vegetation; rains and snows fall upon them; and streams wear them away, cutting canyons and excavating valleys, until at last new floods of rock come to destroy old for- ests, bury old canyons, and fill old valleys. Volcanoes are in this manner built from materials lirought from below as molten lava or as cinders and dust ; but the process is slow and intermittent.

MOUNTAINS. 41

and ouly portions of each vulcanic flood remain in the stmcture of the mountain. When the fires at last cease and the volcanoes are dead, rains and rivei's tear thoni down until the i)eaks are all carried away, and only fragments are l(>ft as columns of \\i\- canic rock formed in the ancient chimneys.

LaccoVific Mountains. — There is another class of \"nlcanic mountains of great interest, though not so common as the vol- canoes already described. Lava coming from the interior of the earth through the crust or i-ock (envelope does not always reach the surface: it may rise through the lower beds, and come with- in a few hundred feet of the surface, and force its way laterally between the sedimentary beds, because the lavas have a greater specific gravity than the limestones, shales, and sandstones of sedimentary origin. As the lavas are forced laterally in this manner between the sedimentary rocks, slowly the upper beds are lifted, and great dome-shaped mountains are fomied with cores of lava or igneous rock, and strata of sedimentary rock arched over them. The cores of lava are called htrcolitcs, and the mountains thus formed laccoUtic mountains. Rains fall on these laccolitic mountains as upon all othei's; and the streams formed thereon carve gorges, and sometimes cut through the sedimentary rocks, and reveal the laccolites within.

Tahle Mountains. — A great sedimentary iilatoau, while un- dergoing gradation by rains and rivers, may be rent by fissures, and lavas poured out. The coulees spread over the surface of sedimentary rocks in this manner prevent for a long time the underlying sedimentary rocks from degradation, foi- the lavas are much harder. As the adjacent country is washetl down, the region protected by coulees remains as a plateau, not very large, and is called a tahle mountain.

liiihrirafed ^fountains. — Such a lava-cut plateau or table mountain may become the core of a greater mountain. Around the flanks of such a low mountain new fissures open, through which lavas are poured, and coulees are thus spread over the flanks of the old table mountain. Still degradation progresses, and the valleys about the mountain are excavated deeper ; and as this process goes on, other coiilees are poured out at still lower elevations. In such manner the core of sedimentary rocks is sheathed with coulees, and a gi'eat mountain is formed with its central body of sedimentary rocks, and its covering of vul- canic rocks.

42 PHYSIOGRAPHIC FEATURES.

Special forms of vulcanio moiiutaius have been described as volcanoes, laccoUtic nioiiiitaius, tahle luoimtaius, aud imbricated mountains.

It must be clearly understood that vulcanism and gradation cooperate in producing ^iilcanic mountains. The materials are thrown out from the interior of the earth, and piled up in irreg- ular masses, and then fashioned by the sculptm-e of waters.

DiASTROPHic MorxTAixs. — AVe have already seen how pla- teaus are fonned by diastrophism. Beds of rock are uplifted, and tilted more or less ; and as great regions are forced up in this manner, the raius fall upon them, and gi-ade them down. Ex- tensive areas that were plains are lifted, and are cut into plateaus by streams, or broken into plateaus by great faults, or di\ided by great flexures. Then these plateaus are still further carved by clouds, whose greater tools are rivers and glaciers, and whose finishing instruments are brooks and rills. With them the diastrophic plateaus are fashioned into mountains, with can- yons, gorges, and valleys intervening.

We have already learned of sedimentary rocks and metamor- phic rocks. These metamorphic rocks were formerly deep-seated. They were at one time sedimentary and igneous rocks, h'ing in strata, gi-eat beds, and masses, and were afterward covered by sedimentary rocks; that is, their stratigraphic place is below the imaltered sedimentary rocks, l)ut in the upheaval of great plateaus these deeply seated rocks have come to the surface, and often constitute the rocks found at the summit of high moun- tains. Mountains of this class often have a core of metamorphic rocks, with sedimentary rocks inclined on the flanks. Some- times the sedimentary rocks ai"e carried away, and it may be that such plateaus were formed in metamorphic rocks where sediments have not subsequently been deposited over them, though this is not known with certainty ; yet we do know that there are mountains which seem to be composed of only meta- morphic rocks, though it is probable that they are only frag- ments of plateaus whose overhing sedimentary beds have been carried away. Many of the mountain ranges of the world have metamorphic cores ^vith sedimentary beds on their flanks. Many mountain ranges are composed exclusively of sedimentary beds, and other mountains of metamorphic rocks, while all vulcanic mountains have another structure.

Thus in diastrophic mountains three varieties are to be noted,

MOUNTAINS. 43

— metamorphic moimtains, mouutaius with metamorphic cores, and sedimentarij mouutaius. Agaiu, we must note that dias- ti'ophisui is the agency by which great lilocks have been up- lifted, and that the minor mov^ntain forms are due to gi'adation.

Grouping of Mountains. — Volcanoes are sometimes isolated, but they are more ofteu grouped in assemblages of gi'eat and small peaks.

Diastrophic mountains are commonly arranged in lines, and are then called ranges. Thv;s a number of mountains may be carved out of a huge wrinkle which would have formed a great round-backed plateau, had it not been for the water. Such great wrinkles are sometimes jiarallel with one another, and thus ranges are grouped into systems of parallel lines. The ranges them- selves may be complicated, and associated with vulcanic moun- tains. The wrinkles of which ranges are formed may not stand abreast of one another, but one may overlap) another; that is, extend beyond it in one direction, while the first nuiy extend be- yond the second in the other direction. Mountain ranges Ij'ing in this shape are said to be in echelon. Parallel ranges and eche- lon ranges are sometimes complicated with vulcanic mountains, and may extend over great geograpliic areas as extensive moun- tain systems. Between the ranges great valleys lie, and between the mountains of every range smaller valleys are formed.

And yet there is another way in which mountains are grouped. A great district of covmtry may be upheaved as a block hundreds of miles long and scores of miles wide. One edge of the block may be much higher than the other; then the streams that gather on the block roll from the upturned mai-gin down with the dij) of the beds into the great valley or plain below, and carve gulches and valleys across the block. Such ranges are moi-e or less transverse to the longitudinal direction of tlie block. Thus great s})urs are formed extending from the crest to the great valley. Such a system of mountains may be composed of more or less parallel ridges that stand abreast of one another in a long line. These ridges usually have culminating peaks on the side where the block was lifted to the greatest altitude. The Sierra Nevada is a system of mountains of this character. Others on a scale less grand are found in various parts of the United States.

Now, it must be clearly undei-stood that in explaining the character of various mountains it is not possible to make a

44 PHYSIOGRAPHIC FEATVKES.

classification which can always be clearly demarcated. It has been shown that plateaus are sometimes partly Aiilcanic and partly diastrophio. As regions are lifted, vulcanic forces are arc)used, so that diastrophic mountains are often complicated with vulcanic mountains. A fissm-e is gi-adually produced, upon one side of which a block is uplifted to be carved into moun- tains. At the same time, lavas are poured through the fissure, and mountains are built. Along such fissui'e a complex range is formed, one side of which is of diastrophic origin, the other side of vulcanic origin ; and the peaks of such a range may be in part \'ulcauic and in part diastrophic. Yet in other but minor ways the two gi'eat classes of mountains are complicated with each other, but it will be clear that mountains express the differ- ence between elevating processes and grading processes.

VALLEYS.

Plateaus and mountains afford the most picturesque sceneiy fur the delight of man, but on plains and in valleys he chiefly makes his home. As plains and plateaus are classified by the great physiogi'aphic processes, and as moimtains are classified in like manner, so valleys fall into three great groups, though this classification must not be understood as implpng that the classes can always be clearly distinguished.

VrLCAXic V-O^LEYS. — AVheu groups of volcanoes are con- structed of coulees, cinders, and ashes, valleys are formed be- tween the mountains. The rains and streams modify these valleys, enlarging them, and excavating stream channels; but the origin of such valleys is to be found in Aiilcanism.

Diastrophic V.vlleys. — "When lands are uplifted in broken blocks or gi-eat folds, the lowlands constitute valleys. Such diastrophic valleys are also modified by gradation.

^lany valleys are inclosed in part by \Tilcauic mountains, and in part by diastrophic mountains.

Valleys of CtEadatiox. — Upheaved plains are divided into plateaus by the corrasion of streams, and the plateaus also are trenched. As time passes on through geologic ages, stream channels ai"e widened into valleys, and a ramifying system of stream channels into gi-eat valleys. Systems of streams uniting with systems of streams carve still greater valleys. Most of the valleys of the world are produced in this manner.

HILLS. 45

Thus we have foiind vulcanic valleys, diastrophk valleys, and fjradatioH valleys. Compound valleys produced by all these agen- cies are found.

HILLS.

Over all the land the hills are scattered. Hills rise from plains, hills are embossed on plateaus, hills are grouped about mountains, and hills are scattered through the valleys. No definite distinction can be made between hills and mountains. The smaller forms are usually called hills; the larger, mountains; but the usage is not consistent. Forms that are called moun- tains ill one region would be called hills in another, and rice versa. Where there are great mountains in sight, somewhat smaller forms are often called hills ; while in another region forms of equal magnitude would be called mountains.

Vulcanic Hills. — As ^nilcanic plateaus are carved into moun- tains, these mountains are still further carved into hills, and we have hills of gradation composed of vulcanic rocks. Vulcanic hills are chiefly of this chai'acter, but there are other kinds that require mention.

Cinder Cones. — As vulcanic fires go out, the expiring ener- gies often Iniild cinder cones; and over a vulcanic region cone- shaped hills are found, often much woi'ii down ]>y rains.

Coulee Hills. — When molten matter is poured over the sur- face of the earth in coulees, it slowly congeals, and slowly moves in great sluggish waves, and the red-hot rock is transformed into cold black I'ock. In this manner waves of liquid rock are frozen into somber hills of low magnitude. So a great coulee often presents a surface of hills and valleys as wrinkles of the waves by which it progresses.

DiASTROPHic Hills. — Uplifted plains form plateaus, and these plateaus are carved into hills and mountains, while the mountains themselves are at last dissected into hills. Thus we have hills in diastrophie blocks carved by waters. The carving of plateaus and mountains into hills is accomi)lislied not only by running water, l)ut also by glaciers.

Diastrophie hills present some interesting relations. As the edges of plateaus are carved, the summits of the hills do not appear above the general level of the plateau itself. Ridges Ije- tween valleys carved in plateaus may be sharp ; and as they are progressively degraded, the more narrow portions may become

46 PHYSIOGRAPHIC FEATURES.

gaps ; and as these gaps are still further degraded, the tops of the hills are lowered. Thus some hills may have theii- summits at the level of the plateau ; other hiUs, below it. As the process goes ou, the whole plateau may be cut into hills of irregular alti- tudes. As the process still goes on, aud the valleys ai'e enlarged, the hills become more unequal in height, and fewer in number. In the same manner mountains are carved into very irregular hills. Thus it is that we may ascend hills in going from lower to higher districts of country, and such hills wiU not have declivities on all sides ; while in older regions of degi'adatiou, where the pla- teau structure is wholly or in part lost, the hills are much more irregular, and it is necessary to descend from ever}' hill in order to reach and climb one adjacent. Hills thus isolated are sometimes called hills of chctondomdutioii, while hills which extend from the summit of plateaus to plains below may be called hiUs of partial denudation.

GiiADATiox-iL Hills. — Glaciers build hills of their ovra. They dig down mountains and plateaus, and carry the material into the valleys and over the plains, and deposit it in hills. The debris carried by gla^-iers forms moraines. "\Mien glaciers melt, this material is left in irregular heaps, and is still designated by the same term. Old moraines are often conspicuous. They are irregular, aud frequently contain hollows which hold lakes. Terminal moraines usually appear as ciu'ved ridges across the course of the ice stream by which they were formed. Lateral moraines form sharp-crested ridges, aud mark the mai'gin of departed glaciers. Other varieties of hills due to the same agency are named with reference to their relation to the ice which formed them.

Besides the more general morainic deposit left by glaciers, there are interesting and frequently very conspicuous topo- graphic forms produced by special agencies.

Long tunnels are sometimes melted out beneath ice sheets, and become filled by streams with gi-avel and sand. "WTien the ice melts, these deposits are left as long, winding ridges, termed eskers.

Al)oi;t the moraines of glaciers where streams discharge piles of gravel and sand, high hills are formed that have billowy sur- faces, and are known as kames. The popular name for a group of kames in certain regions is " kettle hills," in others " cup-and- saucer hills ; " the cups being turned upside down and forming

CLIFFS. 47

rounded knolls, while the saucers between hold water and form lakelets.

As an ice sheet begins to melt, streams may form on its sm*- face, and cut for themselves channels, in which lodges the fine debris imbedded in the ice; and this material sometimes remains in long ridges of loam, called 2)nJ>a in Iowa, where they abound.

Tlie debris carried out by moving ice masses may lodge, perhaps, on a nucleus of rock, and the ice moving over the obstruction gives a smooth whale-back form to the hill. These deposits are sometimes termed lo/tiriilar hills, or dnnn- I'ms. The longer axis of such hills lies in the direction of the ice movements.

These types of hills formed by glacial action are the most com- mon, and are characteristic of many regions, but other forms are known; and in }nany instances the different types are so com- mingled that they are not easily distinguished.

Sand Dunes. — And yet there is another class of hills inter- esting to the geogra])her, formed hy the drifting of the sand by prevailing winds. On the shores of the sea the rocks are ground into sands, and long, fringing sand beaches are produced. Then the winds carry these sands away, some to the sea, and some to the land. Such land-drifting sands are formed into hills, which are known as sand dunes. Lake shores and river banks have their sand beaches, and deserts often present great stretches of naked sand, all of which are drifted into dunes. All dunes travel. The sand is carried from the windward side and deposited upon the leeward side, and so the hills journey. So we have seaheach dunes, lake-shore dunes, strcain-haiik dunes, and desert dunes.

CLIFFS.

Cliffs of Gkadation. — Streams Avith great declivity rap- idly corrade their channels. In cutting down through hard rocks, the banks remain as cliffs. As the process of corrasion goes on, and the channels are cut deeper, the cliffs extend higher above the water. Channels inclosed by cliffs in this manner are usually called canj/ons, the walls of which are cliff's of beauty. But the cliffs break down l)y gravity. The waters percolat- ing through the joints of the rocks, and streaming down the mural faces, gradually break them up; and they fall, and are piled up below in a talus of loose rocks, which is still fnrtlun*

48

PHYSIOGRAPHIC FEATURES.

worn away by rains, and carried into the streams, where it is transported away. lu this manner the canyons are gi-adually >videned, and the cliffs become steep banks, and the channels are then usually known as gulches ; but the gulches themselves

('liffs of tlie (.'anvon tie Tsivi. Arizuiia.

increase in width as the process of degi-adation goes on, until valleys separate the distinct banks, which are themselves carved into hills. Sometimes the banks retreat by a peculiar process

CLIFFS. 49

knowu as sappmg. Harder and more coherent beds above are underlaid with softer and more friable beds below; then the rocks below are carried away more rapidlj^ than those above. Thus the retreating walls are forever undermined, and the rocks break off above by the force of gi-avity, to be ground more or less in the fall, and to be washed away with the talus below. Thus a cliff is maintained which retreats slowly through the cen- turies of degradation. In the same manner the valley is widened continuously while yet waUed with cliffs.

As the land still rises by diastrophism, the stream still cuts by corrasion, and may cut through harder and softer rocks in alter- nating strata or beds. In the upper rocks the cliffs are carried far back from the stream, and another line of cliffs may be es- tablished under the same conditions, the upper part being com- posed of hard beds, the lower of soft l^eds, and another line of cliffs may thus follow the wake of the fii'st. The traveler may climb a cliff wall of a canyon, then walk for a distance, often miles, to a second line of cliff's, which he climbs, and can pass over comparatively level land for a distance, more or less, until another line of cliffs is reached. Thus cliffs rise over cliffs, forming a series of great steps from terrat^e to terrace.

Such cliffs are not regular in the lines of their faces. The river itself is meandering, and so the lines of cliffs are mean- dering. Then lateral streams may' cut through tluMU, running to the main river, and break tliem with canyons; and these lateral canyons also are expanded into valleys, and the teiTaces are thus carved into blocks with retreating walls. The second system of canyons may be traversed by a third system, and the terraces may thus be carved in many ways; and as the process of degradation goes on, the terraces may ultimately be gi'eatly obscured, and at last carved into hills of circumdoniidation, which are huttcs ; and finally the beds may be rcdviced to monuments and bowlders of rock; but canyon walls, teiTace faces, buttes, and monuments of cliff" structure, remain until the region is brought down to low hills. The canyons them- selves are features of grandeur; the cliffs are conspicuous for strange and fantastic majesty ; the buttes present lone, tower- ing forms that chaUenge admiration; and the monuments may appear like gigantic forests of stone tree trunks, gnarled, fan- tastic, and picturesque.

Valleys sometimes extend back into high plateaus. TMieu

50

PHYSIOGRAPHIC FEAXrRES.

the upper surface of such a plateau is of hard rock, and the rocks beneath are soft, the head of the valley may be au amphitheater whose walls are dirt's. Sometimes the traveler may aseeud such a valley from the itlain below uutil he reaches a cliff, when the walls must be scaled, or he must turn to one side and climb the hills, to reach the summit of the plateau. Such amjihitheaters are called cores. Valleys heading in mountains may have coves; when they are refashioned by glaciers, they are known as cirques. On seacoasts and lake shores, sapping is carried on by the waves, and cliffs are often produced.

A Shore C'lifiF on Chesapeake Bay.

DusTROPHic Cliffs. — "WTien gi-eat blocks of land are severed by gi-eat faults, and tilted, the broken faces of the uplifted edges of the blocks stand in great lines of cliffs. Such diastrophic cliffs retreat by dt'gradation through the agency of S!ipi)iug, so that they are finally converted into gradational cliffs, with all the characteristics of cliffs of the first class.

Often they are complicated in another manner. The fissures of the folds by which the blocks are displaced may give vent to lavas which modify and obscure the cliffs. In regions of this character, which are quite extensive in the United States, many of the cliffs of diastrophism are thus in part developed into slopes

CLIFFS.

51

by vulcanic rocks piled against them. Usually tlie coulees pour out a flood below ; but coulees may be piled on coulees, until at last the accumulation of lava becomes so liigh as to flow over the margin of the terrace, and build low mountains along tlie lines of faults. Occasionally in such places volcanic cones are formed. Cliffs of Vulcanism. — Coulees of lava pour from the vent and flow down the slopes of mountains and plateaus. Some

Ejppt"'

'^

A Coulee Cliff in New Mexien.

lavas are excessively fluid, and flow in thin sheets; otliers are but slightly fluid, and flow in thicker sheets; all cool as they flow, until at last they come to a standstill. Wlien the rock ceases to flow in this manner, the lavas behind pile upon it ; and coulees are often formed with very rough edges, which i-onstitute cliffs that may be scores or hundreds of feet high. Such cliffs may

rHYSIOGRAPHIC FEATDJIES.

also be undermined by sapping, and carried back nun-e or less, as in the case of cliffs of degradation.

Thus -we have cliffs of (Iri/raddtioii, cliffs of dhistrophism, and cliffs of nihdiiidiH.

SPECIAL FORMS.

BrTTEs. — Scattered over the land, a great variety of special forms and minor f(>atures are observed which add beauty to the landscape, and interest to the study of the jdiysiognomy of the

lluttc- iRiir till' Sail .Juan Kivi-r, Cnloiado.

land. Hills are found with more or less precipitous cliffs or steep slopes, that stand alone as monuments of circumdeniidation. These may be called huitcs.

Monuments. — ]\Ionuments, or pillars of rocks, are often left standing in the great process of degradation ; for capping stones of gi'eat hardness sometimes furnish protection to xmderlying, softer beds. Such monuments may be tens or scores oi- hun- dreds of feet in height ; and where grouped in large areas, they are sometimes called " monument parks."

Dike AV.\lls. — Sometimes crevices in tiio rocks are filled with lavas from below; then the lavas cool into rocks of a firmer textm-e tlian thos(> of the adjacent formations; afterward, by deg- radation, the softiT rocks on either side are carried awaj% and the lava rocks stand in walls. Lavas intruded in this manner are called dikes, and dike walls are common in volcanic regions.

STREAM CHANNELS. 53

Volcanic Necks. — Volcanic cones are often composed iu large part of ashes, cinders, and readily disintegrated coulees; but the throat of a volcano is usually coated with hard material which has come up in a flood from below and formed a chimney lined with very hard rock, and Anally these chimneys are com- pletely filled witli hard rock. In the process of degradation the exterior and softer materials are carried away, and the filled chimneys of hard rock staml as tombstones of the dead vol- canoes. These are called volcanic necks.

BowxDEUS. — In the corrasion of stream channels and the excavation of valleys and the degradation of hills, bowlders of harder and more coherent rocks often remain behind, while the softer materials are carried away by the waters. Thus the land- scape of hilly regions is often strewn with rocks of many fantas- tic forms, and the remnants of hills and ridges often lie in jjiles of water-worn bowlders.

Great floods also move large blocks of stone, and sometimes scatter them over the valleys ; and wherever stream channels have much declivity, bowlders line the banks and shores, and along the channels are strewn gi-avels worn into rounded forms by being rolled about in the rushing waters.

Glaciers ai'e great agencies in distributing rocks, gravels, sands, and clays over surfaces of land, as they silently creep on- ward, or sometimes move in more rapid progress, to the sounds of breaking and crushing ice.

In the vicissitudes of hill making, ledges of hard rock often protrude through the mantle rock.

Thiis in varied ways the rocks give charm to the landscape. He who understands the sulgect of physiography, and who has his eyes open and his mind receptive to the teachings of nature, not only discovers beautiful forms and wonderful compositions of forms, but at the same time i-eads a lesson of the processes of nature and the great forces silently but irresistibly at work to fashion the earthly home of man.

STREAM channels AND CATARACTS.

Stream Channels. — Wlien the fields are unplowed, the rains wash away comparatively little (>arth. The streams flowing in the forests are held in the grass and under the fallen leaves, and slowly creep away to feed the rivers with clear water; but when

54 PHYSIOGRAPHIC FEATURES.

man comes to gi-ade aiid travel his highways, aud plow aud excavate for his many purposes, the loosened, unprotected eai-th is soon swept away by rains, and fed to the streams. Thus man changes the aspect and regimen of the rivers. Some- times, for various reasons, fields are abandoned ; and these old fields, destitute of their foi-ests and channeled with furrows and ditches, soon become a prey to rains, aud by them the st>ils are washed away, the declivities are cut by a ramification of storm-water channels, while small, naked hills are left behind that are nearly wt)rthless for agriciilture. It is thus that man increases the floods by his labors, and destroys lands by his neglect. All declivities can be injm-ed by careless plowing, and then the richer soils are rapidly borne away.

When the evaporation in any region is almost equal to the pre- cipitation, no streams would be formed, were it not that the rains fall occasionally in great quantities for short periods of time. "When such storms come, a multitude of storm-water streams are produced, which are soon dried up. The more permanent streams have periods of comparatively gi-eat flood and great drought. About the mountains and plateaus, and generally on the highlands, there is greater rainfall, and many perennial streams are found whose waters run to lower lands, where the rainfall is less. Grad- ually such streams lose a part of their waters by evaporation, and, though of considerable magnitude in highlands, become very in- significant in the lands below. It is thus that many creeks and rivei's in the western portion of the United States cany a greater volume of water near their sources than near their mouths. As such streams gradually diminish, the winds blowing over desert plains drift the sands into theu* channels, and greatly choke them. The water coming from above into such sands spreads thi-ough them, and is evaporated. Where this is the case, such regions of evaporation at the end of dying streams are called sinks. Below such sinks the channels may often be lost for a loDg time. Maximum storms come sometimes, — years apart, ten, twenty-five, or a hundred years, as the case may be, — and by these great storms the sinks are sometimes washed out, and the channels below opened again, and the rivers once more flow, to be filled again during long periods of more evenly dis- tributed rainfall. Such buried stream channels are common throughout the western half of the United States, and have caused great wonder to people who do not xmderstand their

CATAEACTS. 55

origin and character. As the streams have diminished, the people have often su])posed that the chmate was changing, and brought in evidence the fact that the rivers were drying up ; or when the streams have been opened by a great flood, and rivers have appeared where they seemed not to have existed before, the people have thought that the climate was becoming more humid, and promised a greater supply of water for the use of man.

Many of the streams of the arid I'egion present another phe- nomenon of great interest. Where the lands are arid, the streams must have steep channels in order to corrade deeply. Many streams have a declivity which would be considered gi'cat in humid lands. Streams so choked by dust storms, and the wash of the naked lands on either side of their channels, are protected from vertical corrasion by the accumulation of mud upon the channel floors. Under these circumstances, lateral corrasion prevails, and wide, shallow channels are produ(?ed. Tliere are streams, like the Platte or the iippcr Arkansas and many other's of the Great Plains, that are hundreds of yards wide and only a few inches in depth at the ordinary stage of water, and never very deep at the highest floods. Such rivers, though they cany an abundance of water, are not navigable. They are ever loaded with new materials by floods and rains, and remain turbid, and often are rivers of mud with channels beset by quicksands.

From the explanation which has been given, it will be clear how streams carve their own valleys. In studj'ing the history of such streams, unless all the facts heretofore set forth are properly un<lerstood, the geogra])her is apt to err in sup- posing that the great valleys are to be explained in another manner. It has often been supposed that they give evidence that in a time long past the rainfall was greater, and that by- secular change the climate has been transformed from a more humid to a more arid condition, and that with the transformation the streams have gradually become less and less. Such errors have gradually disappeared, as the methods of stream cutting have come to be more clearly imderstood. Thus flood plains, old channels, terraces, and retreating cliffs are now understood to be caused by the streams in a long history of valley making, and they are no longer believed to furnish e\adeuce of gi-eater rainfall in antiquity.

Cataracts. Gradational Cataracts. — We have already seen that streams have short, rapid reaches that intervene between

56 PHYSIOGRAPHIC FEATURES.

loiig, quiet reaches. These short reaches are mainly due to the hard rocks which compose their chauuels. In the corrasion of these rapid reaches, the tendency is to cut out the channel at the lower end of the reach to the base-level of the more quiet waters below. This tendency is accented by another condition : if the quiet waters above the rapid are expanded into a bi-oad channel, and especially when lakes are formed, the sediment carried by the river is deposited before reaching the rapid. More and more this sediment is deposited as the iipper cpiiet reaches are ex- panded into lakes, so that the current is almost wlioUj- checked. The load or sediment which the waters contain is the instrument of corrasion; and when this instrument is lost in the quiet waters, corrasion is checked. The waters flowing from the lake above are comparatively pure, and, disarmed of the weapons of corrasion, they pour into the rapid reach. Here they gather new sediments, and aecunnilate them in their passage, so that the farther they flow, the greater the amount of sediment they contain, antl the more Adgorously they corrade. Thus the rapid reaches are cut down progressively from below upward.

At the point 'where the rapid waters meet the quiet reach below, an elbow of declixaty is formed, at the Ijottom of which an excavation is made ; and this basin holds a comparatively large body of water, which is kej^t in motion by the stream rolling down from above. The water of this basin, ever stirred into activity, is constantly undermining the rocks; and the disintegrated material is loaded on the water and carried away, to be deposited not far below. As the basin retreats upstream, it steadily enlarges, and an incipient cataract, or a cascade, is soon produced, the fall of which increases from stage to stage. Now, if this basin is in soft rock, as in clays or shales, while the rocks above are hard, — a condition often found, — then the rapid reach cuts back and increases the distance of the fall until a cat- aract is developed. Most of the great cataracts of the world are formed in this manner, the two most important conditions being, first, that the basin should be in soft rock, and the fall over hard rock; and, second, that the waters should be ponded above in order that the instrument of corrasion should be deposited,, and thus permit the action to be carried on chiefly by sapping.

There is a condition under which cataracts of great altitude are produced, though they usually carry but small (piantities of water. Wlien the great streams carve canyons, and small streams

FOUNTAINS.

57

A Ciitarai't in (ii'orgiii.

enter these canyons, the rate of eorrasion of tlie great stream may gi'eatly exceed that of the small stream ; and thus most interest- ing little cataracts are formed, which often Invak into si)ray before reaching the floor of the canyon, and their own coi-i'asion is thus largely prevented. Streams of water woven into a fili- gree of spray in this manner are often called hrklal veils.

DiastropMc Cataracts. — When streams flow across faults or monoclinal flexures that are in process of displacement, rapids and often well-developed falls are pi'oduced ; but such catai'acts have a short existence. ^\liere the condit ions are favorable, they speedily cut 1 )ack, and become falls of the flrst class.

VHJcank Cataracts. — Coulees of lava freqi;ently pour across streams, and, cooling, dam the waters back in ponds and lakes. Under such conditions cataracts are formed. A few of the gi'eat cataracts of the woi'ld are of this character.

Thus we have c/radatioi/al cataracts, diastrnphic cataracts, and vulcanic cataracts.

FOUNTAINS.

Springs. — Water and air both circulate through the mantle rocks, which are in the main rather loosely aggi-egated. The

58 PHYSIOGRAPHIC FEATURES.

igneous, sedimentary, and metamorpbie rocks are broken into fragments, large or small, by faults and joints, so that there is a circulation of water and air throiigb them also. This un- derground water comes to the surface in i^2^ri>i(/s on low ground, as on the sides of hills, in valleys, and in the banks of streams ; and as the water is supplied cm the surface of the ground, it finds its way down and out by great numbers of springs, but it must be understood that the supply. is primarily derived from the clouds.

Mammoth Springs. — Where there are great accumulations of sand and gravels, forming hills and ridges many square miles in extent, underlaid by impervious formations, mammoth springs are sometimes developed. The rain falling upon the surface sand percolates to harder rock below. Thus rills and brooks are formed on the upper sm-faee of the hard rock, below the sands. Brooks, creeks, and even small rivers may be formed in this manner, and may issue in valleys as mammoth springs. In such a case a single spring may give rise to a river large enough to float a steamboat, the head of the river being a great spring.

In volcanic districts great accumulations of cindei's, espe- cially in mountain cones, present the conditions favoring the fonnation of such mammoth springs.

Hot Springs. — In regions where the rocks at and near the smface are of late volcanic origin, so that the rocks are still hot at a moderate depth, the waters circulating through the fissm'es reach these hot rocks, and hot sjirings are formed.

Geysers. — Sometimes steam accumulates in reservoirs of water below, until it explodes, and the waters are exi^elled with violence in intermittent bm-sts. Such hot springs are called geysers.

Hot water is a gi'eat solvent, and it usually reaches the sur- face strongly charged with mineral matter from the rocks through which it has passed. Cooling in the open air, the water deposits much of its dissolved matter, which often accumulates about hot springs and geysers in mounds, and decorates basins and terraces with beautiful filigi-ee forms.

Wells. — Wells are dug into the rocks to tap the under- ground waters. Waters gathered in such reservoirs are mainly derived from the loose rocks of the mantle, but sometimes wells are sunk into strata pei'\nous to water. All such waters dissolve the soluble materials of rock, especially limestones and iron ores.

CAVERNS.

5!)

Hilt springs of the Vellowstone Park.

Waters charged with hme are nsxially said to be hard, while waters charged with iron are called chalj/hedtc.

Aktesian Wells. — Hometimes a supply of water is dis- covered in this mauuer, whose source is iu distant rocks that come to the surface at higher levels, and the hydraulic pressure therefrom causes the water to flow over the mouth of the well. Such are artesian wells. The pressure may be so great as to throw a column of water high into the air. A spouting well is a fountain of clear water and a fountain of beauty.

CAVERNS.

Gradation AL Caverns. — It has already been seen that waters percolating in hills and mountains dissolve certain rocks. Where this action goes on above the base-level of the country, such run- ning waters flow out by springs, and are carried away by streams. Underground streams are formed in this manner, that carve underground channels, which are enlarged by the action of the waters in dissolving their walls. Thus caves are formed. When a stream comes through some harder rock of limestone, and reaches a soft sandstone that easily washes away, the limestone is undermined as the sandstone is carried away. Then channels

60 PHYSIOGRAPHIC FEATURES.

liaWiig underground streams may be produced on a grand scale, in part in the sandstone below, and in part in the fissured lime- stone above. In this manner great separate chambers are formed in the limestone, with communications below in the sandstone. Such is the structure of Mammoth Cave.

In the walls of canyons and in cliffs formed by all jirocesses, caves are produced by sapping. The softer materials below weather out and are carried away by water, and the harder rocks above are left as overhanging ceUings.

Grottoes of this character are often very Iteautiful, and are sometimes roofed amphitheaters large enough to shelter regi- ments of men. Sometimes springs issue from such eaves and take active part in their production ; and lakelets may be formed which are fountains of cool, crystalline water. In arid lands the vegetation springing up about such springs is luxuriant, while in humi,d lands the mouths of caves are often portals festooned with lichens, liverworts, mosses, and many beautiful flowering plants.

Vulcanic Caves. — Caves are often found under coulees of lava, for the soft earth is easily washed away.

Sometimes the streams of lava are very fluid, and cool at the bottom and upper surfaces much more rapidly than in the inte- I'ior. The rocks thus formed remain, while the interior molten lava flows on, and caves are formed in this manner which are known as volctDt'ic pipes.

Thus we have gradational and vulcanic caverns.

LAKES.

Of the rain which falls upon the earth, a part is evaporated and a part gathered into streams. Along the courses of many streams there are basins, which gather the water in lakes where another part is evaporated.

If these l)asius overflow, the waters of the lakes are sweet ; but if they have no outlet, the waters are salt. Much water evaporates from every lake ; and if the surface is so great as to give an evaporating area suflficient, or more than sufficient, to dry up all the waters coming down in the streams, then no outlet is necessary or possible. But the waters coming from the land dis- solve its salts, and carry them into these lakes ; and as the waters escape by evaporation, the salts remain. Thus gi-eat accunufla-

MAKSHES. 61

tions of common salt gather iu the lakes of arid regions, and hence their waters are saline. We must learn how these basins which hold the lakes are formed.

DiASTROPHic Lakes. — In the displacement of the crust of the earth by faulting and wrinkling, depressions are made, and into these basins the waters are gathered by streams, and lakes are formed. Most of the great lakes of the world are of this charac- ter. Let us call them diastrophic lakes.

Coulee Lakes. — Sometimes volcanic lavas are poured across valleys, and thus the channels of rivers are dannned. These volcanic dams are common, and some rather important lakes are formed in this manner. Geologists call a sheet of lava a coulee. Let us call such lakes coulee lakes.

Cratee Lakes. — Occasionally lakes are found in the craters of extinct volcanoes. Crater Lake of Orego^i is a beautiful illustration, and there are several such lakes iu the nortlnn'u part of Arizona.

Bayou Lakes. — At great flood times, rivers may leave their channels and cut new ones, and afterward the old channel may be closed in such a manner as to form sites for lakes. Let us call these hayou lakes.

Glacial Lakes. — Glacial rocks make dams across vaUeys,and glaciers carve basins. Wlien a region of country is redeemed from the glacial condition by the melting of the ice, such basins are filled with water, and lakes are formed. In the northern parts of the United States a gi-eat many of the smaller lakes are of this character, and many such lakes are found in the Rocky Moun- tains. Let us call them r/Iac/al lakes.

Thus we have diastropliic lakes, coulee lakes, crater lakes, bayou lakes, and glacial lakes.

MARSHES.

Hillside Marshes. — It has previously been shown that the mantle rocks creep down the slopes of hill and mountain. Where the grounds are favorable for their retention, they often accumulate to a gi-eater or less thickness. Into such accumidations the waters percolate from the rocks on the slope above, and from the I'ains that fall on their surfaces. In such manner hillside and mountainside marshes are produced, which are often called hoys, and are quagmires which tremble under the tread of man, and in which many hoofed animals are caught.

62 PHYSIOGEAPHIC FEATURES.

Gi-eat accumulations of this general character sometimes have their lower portions carried away by gradual degi-adation, when their marshy contents j-ield to the force of gi'avity and escape to a region below. Such movements are called laiidslides. They are often destructive to hamlets, gardens and fields, and some- times to domestic animals and human life. "Wlien lakes are drained, their old beds often become marshes in which rank vegetation may accumulate to fonn jycat. About the margins of lakes extensive marshes are sometimes found.

Flood-pl-ain Mahshes. — We have seen how flood plains are gi-aded by the overflo^ving water of streams. The surface left is more or less irregular, and depressions often exist where marshes are formed, and peat sometimes accumulates. Where flood plains are broad, the lands adjacent to the rivers are often higher than the lands farther back. These low gi-ounds nearer to plains and hills often become the sites of marshes ; and it may be ob- served that marshes sometimes sejiarate good agricultural lands near a stream from hilly lands farther away.

Coastal Mabshes. — Coast regions sometimes sink and be- come marshes, or rise out of the sea to form marshes; other coasts are degi-aded until they become marshes ; still other coasts are enlarged by the accretion of sediment to their margin; while fringing islands are produced, and marshes are formed between such fringing islands and the mainland. These coastal marshes are flooded by tides with the salt water of the sea, and they are also flooded by the fresh water of the streams that come from the land. By this cai;se their waters are often brackish. Where the zone of marsh is \\ide, the salt water sometimes becomes fresher and fresher from seaward to landwai'd. In a few regions the salt water is clearly demarcated from the fresh water, for certain trees and other plants grow with great luxuriance in brackish water ; and as they die and fall to the gi-ound, they are filled with shells, the shards of animals, and to some extent with sediments, itntil a bank or di\'ision is established between the waters of the ocean and the waters of the land.

coast forms.

Gulfs, Bays, Sounds, xsd Straits. — The seacoast and lake shores of a sinking land are often deeply indented with bodies of water, while the shores of a rising land are more regular.

ISLANDS. G;J

The islands that stand before the land add niudi to this ir- regularity. Behind the islands and within the indented coast, gulfs, hays, sounds, and straits are found. These terms are used in a very confused manner. There is a tendency to call the larger bodies gulfs and the smaller bodies bays, while there is the same tendency to call the larger connecting bodies sounds, and smaller, narrow connecting bodies, sti'aits. lender these circumstances, no classification by varieties can be made, but only the tendency of usage can Ije jjointed out. All of these bodies may be classified as rulranic, diastrophir, and (/railatioiial. Pkomontoeies, Capes, Peninsulas, and Isthmuses. — High points of land extending into the sea are often called promoiitofies, lower points are often called ca/pcs, and points nearly cut off from the mainland are often called jjciiiiisHtas, while the necks which connect peninsulas with larger bodies of land are often called isthmuses ; Ijut there is no very well estalilished usage for these terms, and the nomenclature is rathei- indefinite. All these forms may be classified in the three gi'eat categories.

ISLANDS.

Vulcanic Islands. — When fires break forth to pour their floods of lava into the waters, they may l)uild up nilraiiir islands. In tropical lands such islands arc; often fringed with coral reefs.

Bakiuer Islands. — Lakes have a special class of islands not found in the sea. When coulee lakes are formed, and valleys are filled with water, the higher portions of the valleys often remain as islands. Thus we have tiarricr islands.

Diastrophic Islands. — When lands sul)side beneath the sea, higher portions may be left as islands. Thus we have islands of subsidence, and we may call them doin/throw islands. In the same manner, when sea bottoms are lifted above the level of the ocean by diastrophic agency, in wrinkling or faulting, the higher i)ortions may first appear as islands. Thus we may have islands of upheaval, and call them iiplif} islands.

Gradational Islands. — When the detritus is brought down from the land l)y streams, it is carried into the sea, and by the currents distributed along the shore, and mingled with the detritus formed by the Ijeatiug waves. In this juanner such detritus islands are often formed. They may be called frinffing islands.

G4 PHYSIOGRAPHIC FEATURES.

A siuking land is itself cut into bills and vallej's. As it goes down, the valleys are filled with water; and the hills may re- main as islanils, or may prosoiit an irregular line of shore to the sea. The waves continually encroach on this shore. Where the rocks are soft, the wear is rapid; where the rocks are hard, the wear is slow. The inlets formed by subsidence are enlarged by the encroaching sea. Two such inlets lying somewhat parallel to each other may send out arms into opposite sides of a tongue of land ; and, as these anus extend backward, they may finally cut off portions of the land and form islands. These may be called (julf-vnt islands.

Streams sometimes change their channels at flood time, new channels being cut ; and islands are thus formed between the old and the new river ])eds, and remain as such until the old channels are filled or blocked, so as to become lakes. Such cut- off islands are very common about the deltas of great streams. Thej^ may be called rirrr-ciif islands.

Again, when lakes are formed by glaciers and the lowlands flooded, the hills may remain above water as islands. Thus we have glacial islands.

An attempt has been made to characterize the physiographic features of the earth, mainly as they are dependent upon the three great physiographic processes, and to show how fire, earthquake, and flood have been involved in fashioning the land and sea.

PHYSIOGRAPHIC REGIONS OF THE UNITED STATES.

By J. W. Powell.

Of a countrj^ so large as the United States no adequate physiographic description can be given within the limits of a monograph of this size. The purpose here is to define the great slopes, and then a greater number of physiogi-aphie regions, which are again divided into districts, and to indicate some of their more important characteristics. Three of the regions have been selected for a somewhat more elaborate description, — one of plains, one of plateaus, and one of mountains, — thus illus- trating briefly all three tyjjes. These regions are the Atlantic Plains, the Colorado Plateaus, and the Pacific Mountains, taking the eastern, a midland, and the wc^stern region.

It will be noticed that an old custom of describing great physiographic regions in units of basins has not been followed. Against that plan there are insuperable objections. Where there are large rivers, there are large basins, and such are again subdivided into ever smaller and smaller basins; and where there are oceans and gulfs, there are many small disconnected basins; so that the basin unit divides the country into very un- equal parts, and fails to exhibit the association of great features that are intimately connected in physiographic history. Grad- ually, as the new science of physiography has grown, physio- graphic regions have come to be recognized; and an attemi)t is here made, by map and verbal description, to define the princi- pal regions of the United States, exclusive of Alaska.

Tlie regions here delineated are held to be natural divisions, because in every case the several parts are involved in a com- mon history by which the present physiogi'aphic features have

(Copyright, 1895, by American Book Company.) 65

66 PHYSIOGRAPHIC REGIONS OF THE UNITED STATES.

been developed. They have been characterized by the more proniiiieiit features used iu the name.

In dividing the United States into a few great physiographic regions, it is not found possible always to draw the lines with exactness. Often one region blends with another, the transfor- mation in general characteristics being marked by a general change. There are some lines of division clearly drawn by nature within narrow limits; other divisions are imperfectly marked by slow gi-adation from one to the other.

DRAINAGE SLOPES.

The United States may be divided into four great slopes, — the Atlantic, Great Lake, Gulf, and I'aci/ic. All the streams of the Atlantic slope drain into that ocean by river mouths within our territory. All the streams of tlie Great Lake slope ulti- mately discharge into St. Lawrence River within our own terri- tory. To the north another region not within our domain is drained into that river, which ultimately discharges into the Atlantic Ocean. This larger division is therefore but partly in- cluded within the L^nited States. The Gulf slope includes all of our territory drained into the Gulf of Mexico. In popular usage, most of this is called the valley of the Mississippi, while small areas are drained into the Gulf by streams not tribiitary to the great river ; and in the southwest there is a district drained by the Rio Grande del Norte, which heads in central Colorado, flows through New Mexico, and then turns eastward, forming the boundary line between the LTnited States and the Republic of Mexico, until it discharges into the GuK. Its waters only in part are caught on the soil of the United States: it is a very small part which comes from Mexico. Along the western boi'der of this grand division the country is arid, having a rainfall of less than twenty inches annually, /n this arid region there are many small streams whose waters are not carried away by ocean- feeding rivers, as the small streams are lost in the sands.

On the Pacific slope all streams that ultimately run to the sea reach the Pacific Ocean mainly within the territory of the United States; but the district drained by the Colorado River of the West reaches the Gulf of California by passing a short distance tlirough Mexican territory. In a large part of the Pacific slope there are many small streams that discharge their

DRAINAGE SLOPES. 67

waters into sands, where they are evaporated and lost from the oceau-reaehiug drainage ; but the valk'vs in which they are evap- orated incHne toward streams draining into the Pacific Ocean.

We thus have an Atlantic slope, a Great Lake slope, a Gulf slope, and a Pacific slope; aiid these terms are coming into common use for the four grand divisions of the United States.

An examination of the relief map of the United States pub- lished by the general government will show that the lines of separation between these great slopes are very irregular. Every- where along them there is an interosculation of head-water streams. Between the Atlantic slojie and the Great Lake slope the divides are sometimes in mountains and sometimes in hills; between the Atlantic slope and the Gulf slope the meandering division line is in part in mountains and in part along the low peninsula of Florida; between the Gulf slope and the Gi'eat Lake slope the dividing line is an inconspicuous elevation, so low in many places that the waters may easily be diverted from one slope to another ; and in late geologic time this change has often occurred, and a part of the drainage of the trreat Lakes has been turned from the St. Lawrence into the Mississippi. The ii-regular divide between the Mississippi region and the Pacific region is sometimes mountainous, with peaks varying from eight thousand to fourteen thousand feet above the level of the sea. The Atlantic slope is a comparativ(>ly uniform d(>- chvity, relieved by plateaus, mountains, and hills that do not rise to great altitudes above the base-levels of the streams. With slight exception, the Great Lake slope is a vast plain broken into subordinate plains Ity terraces and hills. The Mis- sissippi slope has the Api)alachian Mountains on the east, with declivities for its streams that greatly decrease from the moun- tains to the river; and is relieved by plateaus, hills, and moun- tains with great altitudes above the rivers near the Appalachian and Rocky mountains, and has low reliefs nearer the Mississippi. On the north the line of separation from the Great Lake slope is in a single plain, but without perfect uniformity, for there are many terraces and hills. On the west the rim of the basin is in high mountains with lofty peaks, and all along its western border the reliefs are of comparatively great magnitude.

The Pacific slope is in the great Rocky Mountain region. The Stony Mountains stand on its eastern border at the north, separating it from the Missouri drainage. Here towering moun-

68 PHTi'SIOGRAPHIC KEUIONS OF THE UNITED STATES.

taius with a wildeiuess of erags ami peaks appear, over which the snows are mantled for many mouths of the year, and in whose deep gorges he perennial snows. Then the di\'iding line extends between the Platte Plateaus, drained by Laramie River, and the upper extension of the Colorado Plateaiis, drained by Green River, The divide is in the Park Mountains, character- ized by gi'eat peaks, and extends still farther southward across the Colorado Plateaus, and down the Basin Ranges to the Mexi- can line. On the flanks of the Stony and Park mountains there are many volcanic peaks whose fires are noAv extinguished ; still farther westward there are great plateaus and mesas carrying dead volcanoes on their backs ; and still farther westward there are many ranges of mountains, generallj' extending in a north- erly and southerly direction, between which lie gi-eat valleys that are often desert jilains. Then we reach the Sierra Nevada at the south, and the Cascade Mountains at the north, which end the longitudinal ranges and valleys. The Cascade ^lountains are mainly volcanic peaks standing on huge diastroi^hic plateaus, while the Sierra Nevada is a great complex diastrophic plateau carved into transverse ridges by streams that head on its eastern margin and run westward into the valley of California. The ridges between these east-and-west streams are very irregular, and decline in altitude from the east toward the west. In the Cascade Mountains the streams also have a general westward direction into the great Sound Valley ; but there is a region which separates the Sound Valley from the valley of California, known as the Klamath Mountains, through which the streams heading in the southern part of the Cascade region and the northern jiart of the Sierra region flow to the sea without turn- ing into the rivers of the gi'eat valleys. The Sound Valley within the United States is only a portion of a great valley which lies partly within British territory. North of Columbia River and west of Sound Valley stand the Olympic Mountains, and south of that river stand the Oregon coast ranges, some- times called the Oregon Ranges. Thus tlie Pacific coast is ex- ceedingly complex in its great topographic features.

These four grand divisions present interesting characteristics and contrasts, due chiefly to inequalities of rainfall, wliich pro- duce deserts, prairies, and forests.

Deserts. — Plants require great quantities of water for their nourishment. With their roots they drink the water, and

PllAIKIES AND FOKESTS. 69

through their leaves they evaporate it to the heavens. In this process a very small proportion is used by the plant, and built into its tissue. To gi-ow a ton of hay, the grass plants must drink two or three hundred tons of water. The growth of vege- tation depends very largely upon the regularity with which the roots of the plants are supplied with drink. When the rainfall is slight and periods of drought are great, vegetation is scanty ; but when the rainfall is abundant, vegetation is more luxuriant. Temperature is another factor in the rate of growth. With liigh temperature and gi'eat rainfall, the most vigorous vegetation is produced; with low temperature and sliglit rainfall, more scanty vegetation is found ; but if the rainfall is very small, high tem- perature serves rather to increase aridity and the desert con- dition. In tlie temperate zone, if the rainfall is less than ten inches annually, the desert conditions prevail ; but, though the rainfall may be less than five inches annually, the desert will yet afford some clas.ses of plants, like the iigave, yucca, and cactus.

Many desert plants are covered with a kind of bark, the poi-es of which close in times of aridity so as to prevent their water from being evaporated. Other ])lants have a hal)it of rolling up their leaves and 'folding their stems in such a manner as to present the smallest surface for evaporation. Nearly all desert plants are furnished with thorns, and many with acrid juices that protecit them from being devoured by animals. So the plants struggle for existence. The animals of the desert are few, though some insects and some reptiles abound ; and among them many cnrious forms may be observed.

Deserts are l)eset with dunes formed of wind-blown sand. Sometimes deserts have scattered over their floors pebbles, which are the remnants of formations carried away by degrada- tion. They are worn fragments of very haixl rocks, often crys- talline and of many colors. As the sand sweeps over them, the pebbles are polished, and the desert is sometimes floored with a mosaic of brilliant gems.

Prairies and Forests. — As the rainfall increases from ten to twenty inches, grasses and various other plants are multiplied, and become more and more luxuriant; and low, gnarled trees, especially cedars and pines, are developed, if they arc protected from fires. As the rainfall increases from twenty to forty inches, forests increase ; that is, they are extended over greater areas, and the trees themselves have a more rapid growth, and attain

70 PHYSIOGKAPHIC REGIONS OF THE UNITED STATES.

larger size. In such regions ^ngorous forests will gi-ow, if they are protected from fire. The gi-eat prairie region of the United States is found mainly where rainfall is from twenty to forty inches, because the forests are destroyed by fire. Going from the more arid to the more humid regions, forests become more frequent and more vigorous; and e8i>ecially are trees found near streams, and where the lands are hilly, broken, and stony, so that luxuriant grasses are not abundant, to furnish food for fire.

Since the prairies of the United States were settled, gi-eat changes have been wrought in the landscape. Protected from fire by the plowman's furrow, trees have sprung up everj'where ; so that to-day, throiigh all that region stretching from the Ohio across the Mississippi and across the Missouri on to the Great Plains, the forest areas are rapidlj' nuiltiplyiug, and planted gi'oves are common. It is thus that cultivation protects forests, and furnishes the condition for foresting lands which were prai- ries in their primeval state.

When man attempts to preserve lai'ge forests without pro- tecting the ground with the plow or by other agencies, he usually fails. To save the forests, he carefully tries to prevent fires ; then grass, leaves, bark, twigs, and boughs gather upon the surface of the earth from year to year, until a thick coating of infiam- mable material is formed. Immunity from fire thus furnishes food for fire ; and when a dry season comes, an accidental spark starts a great conflagi'ation, which spreads with the wind as only "wildfire" spreads, and the great accumulation of combi;s- tible matei'ial makes a sweeping flame which destroys everything before it. It is thus that the forests of the Northwest, which are largely held for lumber purposes, are subject to fires that destroy property on a great scale, and even destroy human life.

Where the rainfall is sufficient protection, and fires are not kindled, forests prevail. In soixthern latitudes and low altitudes the trees attain a greater size than in noi'thern latitudes and high elevations; but there are some important exceptions to this general rule. In Washington, Oregon, and California, gigantic forests are foi;nd developed by humid lands that lie near the Pacific coast, while other gi'oves of great trees stand on the slopes of the Sierras that face the great ocean. Where the mois- ture is more than fifty inches, and where other climatic condi- tions are favorable, dense forests of gigantic trees, with tangled masses of undergrowtli, stretch over the land. In the great

PRAIRIES AND FORESTS. 71

valley of California, live-oak groves abound, and the trees are gnarled and picturesque. In more arid lands, groves of low, spreading, gnarled pinons and cedars are scattered at wide intervals. In early time, before the prairie region was settled, there were found groves of low, spreading l)ur-oak.s, that from a distance looked like orchards ; and in fact they were orchards of acorns. In the humid lauds, and especially in the tropic lands of Florida, the great trees are often draped with festoons of " Spanish moss," and decorated with beautiful orc^hids. In the valley of the Ohio, magnolias spi'ead their blossoms as goblets of perfume. All over the Alleghany Plateaus, the Appala«'hian Mountains, and the Piedmont Plateaus, great tulip trees stand, with stately boles and light branches that bear most beautiful flowers. In every flood plain of the I'^uited States, sycamores with smooth trunks, broad arms, and expanding leaves, spread a sweet shade over the gi'ound when the summer sun is fien-e. By every river, creek, and brook t\n) willows stand, and dip thoir delicate leaves into the nuirmuring waters. In the ponds and lakes of the United States, water lilies grow, and on all the hill- sides roses bloom. Late in the summer tlie goldenrod Imrsts into flame along the northern border of our land; and as tlie weeks and months pass, the zone of gold sweeps southward until it is stopped by the Gulf.

Before the settlement of America by the P]uroi)eans, while the land was yet under the sway of savage tribes, the whole country was annually burned over, ami wherever forests could be destroyed they W(*re swejjt away ; but when the lands were plowed, the fires were stojjped ; and vast regions that were prairies at that time ai'e now forest-clad. To-day the forests of the United States are somewhat more extensive than they were at the landing of ('olumlnis. While the prevention of fires saves- some trees, the ax fells others, so that many forest r(>gions have been transformed into fields ; yet to-day fli-es destroy more trees than the ax.

The growth of trees depends upon rainfall, but i>art ly also upon care. Seeing that arid lands are treeless, many observers reach the conclusion that aridity is due to the destruction of the for- ests. The (>ffe('t is nnstaken for the cause. This superstition has widely prevailed, and many of those who have not studied this subject believe that rainfall can be increased by the planting of ti'ees. This subject has l)een most carefully and thoroughly

72 PHYSIOGRAPHIC REGIONS OF THE UNITED STATES.

iuvestigated by scioutifie meu, aud they are not able to discover that the presence or absence of trees either increases or dimin- ishes the rainfall ; and yet this mj-th is told all over the land.

On the Atlantic slope primeval forests were discovered in the early settlement of the country, and a few of the valleys were prairies. Forests were mainly open, without dense under- growth, as they were annually burned by the Indians. Since the settlement of the country, gi'eat areas have been cleared, and prairies have been brought under the plow. The forest lands that remain have been protected from fires, the under- growth is preserved, and open forests are no longer seen. Here the forest area is smaller than at the advent of the white man, but the number of trees is nearly as gi'eat.

The Great Lake region also was mainly covered with forests when the country was settled by civilized people; but the groves were open, and the trees were comparatively low and gnarled, as they were ofteu singed by fires. The primeval forests are nearly gone, much of the country is under the plow, but the new forests present changed characteristics. The new trees, densely crowded, compete for the light of the sun, and gi'ow to greater heights; and the ground below is covered with dense foliage and tangled imdergrowth. Here also the forest area has been reduced, but the number of standing trees is perhaps as great as in primeval times.

The greatest change has been wrought in the Mississippi slope. Its northern and central portions were mainly a prairie region, and extended to the foot of the Rocky Mountains. The few forests to the north, the greater wooded regions on the flanks of the Appalachian Mountains, and the more imposing forests on the south, protected from fires, have increased in the • number of standing trees, though great fields have been cleared for agriculture. Throughout the prairie region the river-border groves have become more dense, and the trees more stately. From these groves the native forests have spread over a large aggregate of ground, and many groves and orchards have been planted. Though this prairie region is densely settled and much of it cultivated, the groves have lost their primeval character, and the vigorous trees have multiplied to an astonishing degi-ee.

The Pacific slope presents great contrasts in its southern part, where there are extensive areas of desert. The mountains and high plateaus are everywhere covered with forests ; and on

THE ATLANTIC PLMNS. 73

the slope of the Sierras groves of giant sequoias are found, while near the coast towering redwoods appear. In western Oregon and Washington, yellow pines, redwoods, and cedars, and many- other stately trees, flourish in the warm, humid lands that are supplied with moisture from the Pacific. On the Pacific slopes we have dreary deserts, prairie valleys, and gigantic forests.

THE ATLANTIC; PLAINS.

A monoclinal flexure extends fi-om iha Jersey side of Hudson River near the city of New York, southwestward i^ast Trenton, Philadelphia, Baltimore, near the falls of the Potomac, above the city of Washington, where the line curves in a more southerly direction to Kiclnnond, Weldon, Raleigh ; and turning westward, it crosses Savannah River near Augusta, and gradually disap- pears in the region of Macon, Ga. This geologic feature extends in an indefinite way past Montgomery. It is easily followed by the geologist from New York to IMacon, past the streams tliat flow into the Atlantic, until streams are reached which faU into the Gulf of Mexico. Tliis line of disphicement has an interest- ing geologic history. The rocks to the west and northwest are of Archaean age; the rocks to the east and soutliwest are mainly of Cretaceous, Eocene, and Neocene age. The line or narrow zone separates hard, dark, crystalline schists, traversed by veins of white quartz that are of ancient geologic formation, from gravels, sandstones, shales, and clays, that make up the rocks of later origin. Since the beginning of Cretaceous time, a zone extending from the monoclinal flexure to the sea has passed through several vicissitudes of history, at times being dry land as it is now, and at times being sea bottom. So the shore of the sea has oscillated slowly back and forth across this part of the Atlantic Plain. Along tl|e advam-ing and receding coast, gravels have been piled by streams coming from the landward side, and with them sands and clays have been deposited ; ])ut the finer materials have always been carried farther into the sea, and, the coarser materials left near the shore. In studying the rocks of which th(^ plain is composed, as they are t^xposed in stream banks and blulfs, and as they are revealed in digging and boring wells, alternations of gravel, sand, and clay are discovered ; and the gravels usually increase in thickness toward the northwest, and thus appear to be shore deposits along an advancing or re-

74 PHYSIOGIUPHIC KEGIONS OF THE UNITED STATES.

t'L'ding coast. Distinguished so clearly by geologic features, the topogi-aphic characteristics of this zone are even more plainly marked. The line of flexure is everywhere more or less clearly deliued as a terrace broken by valleys and stream channels. In the streams the line is still more marked, for everywhere they cross it in rapids and falls. Far above there are rather swift- flowing but ([iiiet reaches; at the flexure they plunge down with rolling, tui-bulcnt currents, and fall into broad channels with placid waters. Below, all the streams of magnitude rise and fall with the tides ; above, all the streams rise and fall with the great storms ; while along the narrow zone of flexure the clear waters are transformed into rushing torrents by long-continued rains. Here we find the gi-eat water powers which have been utilized ever since the early settlement of the country ; and here we find the barrier to navigation, for the vessels that come from the Atlantic coast cannot be navigated across the fall line, and all boat transportatioii from below ends here. A few of the streams can be navigated above this line ; but their cargoes must be car- ried over the fall line and reshipped, to reach the sti-eams below. The zone of displacement is thus marked by characteristics which divide the country above from the coimtry below in a double way. It is the zone of water powers and the zone of interrupted trausjjortatiou by water. Under these circumstances the fall line was well marked in primeval times, evo yet the white man had settled in the land, for a line of Indian villages extended along it from the Hudson to the Savannah. Later, under the aegis of civilization, cities were built at this line, with convenient water power for manufacturing purposes, and easy means of commerce with the old country by the sea, and with the interior by rivers, canals, and roads. Thus, ^^ncousciously to the savage and un- consciously to civilized man, geologic conditions fixed the sites of ancient villages and modern cities at the head of tide water and in the region of the great water powers. From this fall line a great plain extends to the coast, jnarked by few hills, and slightly terraced witli bluifs on the margins of flood plains. Near the coast and along the flood plains extensive marshes are found. This irregular zone of marsh is clearly distinguished from the higher plain. A lower plain extends from the coastal marshes out to the sea for many miles, until at last shallow waters change into deep waters, and the bottom plunges down Avith steep declivity into the depths of the Atlantic. This

THE ATLANTIC PLAINS. 10

Atlantic plain is therefore naturally divided into three great zones, — the subaerial portion; the marsh portion, which is cov- ered more or less intermittently witli water by tides and storms ; and the suhmaiine portion, which extends out to deep waters.

Above the city of New York the marine ijortion of the plain expands, while the marsh portion is usually narrow, though some- times it extends back into the high land many miles; but it is often broken, when higher lands extend down to the tide, and the submarine plain is separated from the subaerial plain only by sea cliffs. In this northern region the land portion of the plain is very irregular: in some jtlaces it is naiTow, in other places it expands to considerable width, but altogether it is much less conspicuous than it is below the Hudson. South of Macon, Ga., there is an irregular line of parting between tlie waters of the Atlantic and the waters of the gi-eat Gulf. That portion which drains into the Atlantic is still called the Atlantic Plain, and it thus embraces a part of Florida down to the Keys. Oft" southern Florida the submarine portion is greatly narrowed, while the marsh portion expands into the gi-eat marshes of Florida, which extend from the ocean to the Gidf.

The land plain is usually rich agricultural land, and is exten- sively cultivated. The marsh plain has a wealth of deep soil, and wherever redeemed by drainage or embankments it yields bountiful returns ^to agi'icultural laVior. The sea plain is the site of a coastal commerce which has already attained great magni- tude, and which is steadily growing. The scenery is monoto- nous in relief, but wonderfully varied with bays and gulfs, and broad, quiet rivers, the banks of which are diversified with stately groves. From the palmetto of the South, to the low, gnarled oaks of the North, there is a i)aiioi'ajua of ever-changing forests. At the South, coral groves abound, which unite with sediments from the land to build fringing islands. Northward from the coral homes great rivers loaded with sediment supply sands that iire deposited liy the currents, and by the waves are built into other fringing islands all along the marine plain until we reach the great sand banks of the North. In a few places there are diastrophic islands, and behind them there are great harbors, as in New York Bay. Especially along the coast of New England there are many diastrophic islands, and from New York to Bos- ton they protect quiet sounds that are utilized by commen-e in great fleets, whose white sails skim the sounds all summer long.

7(3 PHYSIOGRAPHIC REGIONS OF THE UNITED STATES.

Aloug the coast of Maine the tides sometimes rush up the rivers iu gi-eat bores, and the rock-bound coast is protected by sea cliflfs. On this beautiful Athmtie coast the traveler may sail from coral reefs to seas where icebergs float, and may retui'u by the steel highway from cranberry gardens to orange gi-oves.

THE PIEDMONT PLATEAUS.

The Piedmont Plateaus lie west and northwest of the central portion of the great Atlantic Plains. The rocks of which they are composed are maiiilj' of Aix-hjean age, and are all more or less metamorphic. Often they are of slaty structure; that is, the sedimentary beds originallj- laid down in strata have, by diastrophism, compression, and chemical change, become meta- morphosed; ofttimes the old stratified structure has been de- stroyed and a new structure imposed upon the rocks, so that they appear iu thin plates which do not conform to the old stratified planes. This structure, given by metamorphism, is known as slaty structure. Besides the original sedimentary beds, primarily there were gi-eat l)odies of lavas, and these also have been metamorphosed. During Cretaceoiis time, while the Atlantic plains to the eastward were sometimes land plains and sometimes submarine plains, and while the coast line was shift- ing back and forth, the Piedmont region a^ degi'aded to a gi'eat system of i)]ains which were traversed ^^^treams running to the sea. The whole plain seems not to have been brought down to the level of the sea, but to have inclined slightly to sea- ward aud toward the valleys of the streams; so that, iu refer- ring to its plain condition, the region is often called a peneplain. When the land portions of the Atlantic Plain were finally un- masked by the upheaval of the land aud the retreat of the sea, the same system of upheaval extended throughout the Piedmont region, and has continued with intermission to the present time, until the old plains have now reached an altitude which consti- tutes them plateaus, as that term is now (h^fined. We have already shown that the Piedmont region is narrowly defined on the Atlantic side by the fall line, which separates it from the plains. On the northwestern side it is bounded by the Appa- lachian Mountains. The line of separation between these two regions is not always as clearly defined as that on the other side, and yet in the main it is distinct.

THE PIEDMONT PLATEAUS. 77

The region had a great extension of plains, sometimes diver- sified with many hills, before its upheaval into the plateau condi- tion. In various places there were areas of quartzite whit-h were hard and unyielding to degradation, and which remained as hills. In other regions there were bodies of firm granite, probably of volcanic origin, which also resisted degradation and remained as hills. Over the old plain surface these ancient hills still remain to crown the plateaus. As the upheaval began, the plain was tilted eastward, and the sluggish streams were urged to greater activity, until they became swiftly rolling rivers and creeks, and even the brooks danced in joy with the new activity. Witli this new-born life they began to corrade their channels and to cut them in deep gorges, and griidually they carved out valleys, and divided the old plain into plateaus separated by luxuriant valleys with meandering stream channels and flood plains ; wliile the hills on either side ascended to ancient plains, now plateau summits with their embossed hills. As corrasion pres.ses hard upon upheaval, channels are cut more rapidly than the general surface is disintegrated and washed away, and for this reason the lateral stream gorges and valleys have a slightly convex profile; but when' upheaval ceases, convex pi'ofiles are slowly changed to concave profiles. By this characteristic geologists often discover important time relations l)etween diastrophism and degradation. From these cliaracteristics of convexity and concavity, and from certain related facts, it is known that the Piedmont Plain was not upheaved evenly and simultaneously in all its parts, l)Ut that it was lifted now at one place and now at another. Where first lifted, the gorges and valleys are convex ; where last lifted, they have concave profiles. There is not space here to characterize fully the Piedmont region in this inspect, but reference will be made to one of the districts which has been uplifted in very late geologic times.

The Susquehanna Eiver, wliich deboiiches into the head of (Jhesapeake Bay, is well marked by rapids at the fall line near its mouth ; but above, swift waters continue, crossing the Pied- mont Plateaus uji into the mountain region. In late geologic time, tide water extended throiigh tins reach of the river in a broad, shallow channel which carried fresh water fi'om above. By the last upheaval and tilting in tliis stretch from the fall line into the mountains, the flow of the river was accelerated, and the swift waters have mainly swept away sediments that

78 PHYSIOGRAPHIC KEGIONS OF THE UNITED STATES.

had accumulated on the bottom of the channel and along the old flood plain. Yet this upheaval was late, and may be yet in progress ; so that sufficient time has not elapsed to carve a new channel in the old rocks below, but only enough to carry away the greater part of the soft materials, — the ooze and sediments that gather on the bottom of the old broad-cut river. The old bottom of hard rocks was very irregular as a floor; and as the soft rocks have been carried away, this irregular surface ap- pears. Many channels in the hard rocks have been cut, and the irregularity is now even greater than it was originally. For this reason the Susquehanna falls into a very broad, shallow channel, beset with gi-eat bowlders and bordering ledges of rock ; and it often runs in many channels, while patches of sedi- ments that lined the old river bottom still remain here and there. It is thus that history is recorded in river channels, graved in ghi)lis l>y corradiiig streams.

Many fissures in the metamorphic rocks of the Piedmont Plateaus have been filled by the deposition of white quartz onc.e held in solution in the underground waters. In this manner extensive veins of the white crystalline mineral ramify through the rocks, which are usually dark and somber, but are enlivened with the veins of crystalline quartz. In these veins minute fragments of gold are discovered throughout the Piedmont re- gion. Ever the shining metal has attracted the eye of ciAilized man, and gold mining has been extensively practiced; but the quantity found has never been very great, and usually the quartz veins have failed to renumerate labor.

THE APPALACHUN RANGES.

These ranges extend from southern New York into the State of Georgia. On the southeast the Piedmont Plateaus stretch from the foothills of the mountains. On the northwest the great Alleghany Plateaus lie, joining the Lake Plains in the re- gion of the Gre;at Lakes, and the Prairie Plains in the region of Ohio River. These mountain ranges are composed mainly of ridges whose longitudinal direction is from the northeast to the southwest. Between these ridges valleys are found. Usually a valley separates the mountain region from the Alleghany Pla- teaus. This system of mountains is naturally divided into two parts, the northern Appalachian and southern Appalachian

THE APPALACHIAN RANGES. 79

ranges. On the north the streams heading in the Alleghany Plateaus run southeastward into the Atlantic Ocean, and cut through the ranges by great gorges that are popularly called ■water gaps; but south of New River the Appalachian Ranges are drained into the Gulf. The streams head in the crest of the most eastern rauge, and cut through the ranges to the west by flariug gorges, and most of them empty into Ohio River by the waters of Cumberland and Tennessee rivers. In early Cretaceous and Juratrias time the Appalachian Mountain and the Alleghany Plateau regions were reduced nearly to a base-level. In Creta- ceous time these regions were again lifted ])y diastrophic agen- cies. The northern plateaus were tilted in a manner which turned their waters toward the Atlantic, while the southern plateaus were lifted in such a manner that their waters were turned toward the Ohio ; so that now we find the Delawai'e, the Susquehanna, and the Potomac rising far to the northwest in the Alleghany Plateaus, and flowing southeast across the Appa- lachian Ranges to the Atlantic, wliile New River and the tril)u- taries of the Tennessee rise far to the southeast in the Blue Ridge, and flow northwest across the Appalachian Ranges and the plateaus beyond to the Ohio. The two portions were further differentiated by reason of a gi'eat distinction between the meth- ods of interior diastropliism. The folding of the northei'n Apjia- lachian Mountain belt was more regular in great anticlinal and synclinal flexures, while in the upheaval of the southern moun- tains the folds were crowded together and often faulted on a gigantic scale. These ancient folds were planed down wlu>n the whole region was lirought nearly to a l)ase-levcl, and the new val- leys cut on the later upheaval were carved mainly in soft rocks, while the mountains that are left are composed mainly of hard rocks. The valleys, therefore, do not follow downturned flexures, but lie along out-cropping edges of hard beds, while the streams themselves from time to time cut through the ranges by flaring gaps. In the same manner in the southern mountains, hard rocks make mountains, and soft rocks produce valleys; but these val- leys ai'e less regular below, because of the great lateral thrusts by which the strata were closely plicated and often faulted. TTsually the valley between the mountains and the Alleghany Plateaus is wider, and is a more conspicuous feature, than the other inter- range valleys. The ridges themselves are rather monotonous mountains, but in the water gaps picturesque -sceneiy is found.

80 PHYSIOGR.\PHIC REGIONS OF THE UNITED STATES.

The valleys that are regular and beautiful are highly cultivated and densely populated.

.AXLEGHANY PLATEAUS.

In a broad way these jilateaus are carved out of a great block of sedimentary rock tilted to the northwest from the Appa- lachian Mountains down to the Prairie and Lake plains. In Cretaceous and Juratrias time the block was graded to a plain, the surface of which generally conformed to the stratification. The gi'eat block is slightly warped, and there are many local evi- dences of minor diastrophism. In general the plateaus are crossed by deep, comparatively narrow water channels. As the streams run in deep channels, all the larger ones being in gorges from two hundi'ed to a thousand feet in depth, the dissection of the plateau block is often miniite, and many plateaus are thus formed. The region of the Piedmont Plateaus, Appalachian Mountains, and Alleghany Plateaus, in its earlier geologic his- tory, extended farther to the northeast, and gradually faded out ; but its structure is still preserved, though more or less masked by glaciation. It is even to be observed in the Green Mountains of Vermont, as well as in the Berkshire Hills of Massachusetts, which constitute a part of the Green Mountains. But north of the Piedmont Plateaus the region has been carved by glaciation and masked by glacial hills, so that it is best described by itself.

NEW ENGLAND PLATEAUS.

In this and the two preceding monographs mention has been made of the action of glaciers in grading the land, but the sub- ject did not receive adequate treatment for want of space. Yet in characterizing the physiogi-aphic regions of the United States it becomes necessary to say something more of the action of ice, and of the history of a time known as the glacial period.

The most of Greenland is now covered by ice. Ice is found over great areas of the northern extremity of this continent and far down the Pacific coast. At different times in the Pleistocene period this ice capping of the land reached much farther south- ward. There was one great body of ice, known as the Lauren- tide Glacier, which extended over Canada and other parts of British America down into the United States, its most extreme

NEW ENGLAND PLATEAUS. 81

lobe reaching to a point in the Mississippi Valley not far from the mouth of the Ohio. Geologists have shown that it covered an area of about three milliou square miles. There were other great glaciers farther west which we need not here consider.

The Laureutide Glacier endured for a long time, and passed through many phases of history. Perhaps it existed at two or three different times, with intervening periods of milder climate, when it was melted. In its greatest development it must have accumulated to a thickness of hundreds or thousands of feet. Its different portions were ever moving on the surface of the land, and grinding up the rocks below, and pushing them down the slopes in a general way to the southward, with many variations. The rains fell upon this glacier through the centu- ries, and the sun melted the ice, and the water percolated to the surface of the ground, and flowed away in subglacial streams that carried with them the rock-flour gi-ound by the ice, which was armed with rocks carried along by tlie ice. It is thus that the great glacier served as a mighty agenciy for the degradation of the land, pushing the bowlders and ground material along its bottom, and carrying it away in channels, often piling it up in moraines, drumlins, kames, eskars, and other forms, and spread- ing the finer materials in great sheets of clay and fine sand.

A portion of the Laureutide Glacier was expanded over New England and New York down to the very site of the great city. Over this region it extended for a long time, though its existence may have been intermittent; but it remained long enough to accumulate masses of ice with power to perform the stup«>ndous task of refashioning the surface of the land. It found mountains, plateaus, plains, valleys, and hills, but it changed them all by carving new forms to its own liking ; but, more than all, it bi;ilt a vast army of hills, and filled many valleys. The modified moun- tains yet remain ; the old plateaus, though changed, still stand ; but the valleys and hills are to a large extent new features. I have called this region the New England Plateaus ])ecause before tlie advent of the ice it was a great group of plateaus diversified with mountains, hills, and vallej^s. Now new hills are found widely scattered over it, sometimes in its valleys, always over its plateaus and over the flaidvs of its mountains. The Adirondacks still stand, much modified by glaciation. Down Vermont the Green Mountains extend into the State of Massachusetts, where they are called the Berkshire Hills. Everywhere they have been

82 PHYSIOGEAPHIC REGIONS OF THE UNITED STATES.

remodeled by ice. Still to the east, in New Hampshire, are the White Mouutains, with Mouut Washiugtoii as a culminating peak ; and there are loue raouutaius scattered over Maine, and the region extends beyond our boundary into British territory. The structure of these plateaus is more or less masked by glacial hills, and there are great valleys with river plains exhibit- ing fragments of ancient glacial hills. Near the Atlantic the coastal plain is broken, and many sea cliffs ai-e found, and the coastal marshes are very irregular. In New York, glacial valleys and more recently cut river valleys are found, and limited plains are seen, especially in the region of the Finger Lakes. Scattered through the region are many lakes of clear, cold, beautiful waters ; and there are many marshes, some fed by the tide with salt water, but many more with fresh water; and the interior lakes are mainly of glacial origin.

LAKE PIAINS.

In the northern portion of the United States there is a lake region which extends still northward far into British America. In the midst of the region lie the Great Lakes, — Ontario, Erie, Huron, Michigan, and Superior; and about them, to north, south, east, and west, many others are found of less magnitude, to the number of thousands. The region is in large part drained by the St. Lawrence, and in small part by the Mississippi. The Great Lakes are primarily of diastrophic origin, but they have all been remodeled by ice, while the smaller lakes are due mainly to glaciatiou. The gi-eat Laurentide Glacier extended over all this region, and buried it deeply under the ice, and during its history made gi-eat changes in the land surface by degrading old forms, and building new lands.

Previous to the advent of the glacial age, the region was in the main a system of great plains, with hills and some minor plateaus ; but when the ice came, it covered them all, and wrought a regeneration, leaving the Great Lakes still lying in their dias- trophic basins, but adding to the region a vast assemblage of glacial lakes, many of which remain, while many have been filled with peat, and drained by new stream channels. The plains left by the glacier were low, with comparatively little relief.

Since the disappearance of the ice sheet, diastrophism has progressed as of old; so that the Lake Plains have been warped,

PKAIKIE PLAINS. 83

and it becomes easy to identify these diastropliic changes. As it is a region of many lakes, and as the streams liave all been corrading new channels since the disappearance of the ice, the great and small lakes have often been terraced. The greater plains have in this manner been cut into small lake plains that, are low stairways from shores to high lands. Thus the region is characterized by great plains base-leveled in earlier geologic periods, releveled during the glacial period, and terraced with lake plains since that time. By reason of its many lakes and its numerous terraces, it is well characterized as the region of Lake Plains. Four districts may be recognized, as shown on the map.

PRAIRIE PLAINS.

On the south and on the west of the Lake Plains stretch the great Prairie Plains. When this region was first visited by white men, much of it was destitute of forests. In the east, glades and small prairies existed ; farther westward the prairies became larger, until, in eastern Indiana, the prairie region pre- vailed in extent over the forest region, while beyond the Missis- sippi the prairies were interrupted only l)y the groves that border the streams. This pniirio region sweei)S around the great Ozai'k Hills, and extends southwai'd nearly to the Rio Grande del Norte. Here and there it is relieved by low hills, and it is cut with a labyrinth of stream channels, on the borders of which flood plains appear that were usually covered with trees in the olden time. The Laurentide Glacier extended across this prairie region down nearly to the mouth of the Ohio; and wherever it was spread, great glacial accumulations apjx^ar as beds of clay, sand, and gravel, and sometimes as glacial hills. On the last reti'eat of the ice there were left behind many little b;isins, into which the waters were gathered; and a multitude of little lakes were thus formed, many of which were gi-adually drained by the streams, and filled with peat. It is thus a region of small extinct lakes, whose shores Avere rarely terraced because of the l)rief life awarded to these little bodies of water.

On the west the prairies merge imperceptibly into the region popularly known as the " Great Plains," but which we now call the Great Plateaus, for the reason hereafter to ajipc^ar.

The lands of the prairies are fertile. Douglas Jerrold said, that, if you tickle them with a plow, they will laugh with a liar-

■84 PHYSIOGRAI'HIC REGIONS OF THE UNITED STATES.

vest. When the couutiy was first settled, the districts far away from standing timber were supposed to be almost uninhabitable for the want of fuel and timber ; but under the prairies vast coal fields have been foimd, and the men of the prairies have learned to fence with hedges and iron wires, and they have built railroads, on which they have carried the lumber necessary for their homes. The agricultural industries of all that land have flourished. Gradually the lowlands have been drained and tilled and the higher lands have been plowed, forest groves have been planted and the old woods have spread, thousands of orchards have been gi'own and vineyards have been jilanted and gardens cultivated, until a greater proportion of the land has been brought under the plow than that of any other region of the world of the same magnitude. Two districts are shown on the map, — the one glaciated, and the other not.

THE GULF PLAINS.

On either side of the Mississippi Eiver, from a little above the mouth of the Ohio, a great plain stretches to the south, and expands to the Gulf waters. On the east the border of this plain skirts the Alleghany Plateau and the point of the Piedmont Plateau, and extends east to the line of parting waters between the Atlantic and Gulf drainage, which it follows into the marshes of lower Florida. On the west it flanks the foot of the Ozark Mountains, and continues southwest ward to the Rio Grande del Norte. iVll of this area we call the Gulf Plains. Down its middle the Mississippi runs, and along the Mississippi and up its important trilnitaries there is a great flood plain. Thus the Gulf Plains are divided into five gi'eat districts, — the East Gulf Plain, iho West Gulf Plain, the Flood Plain of the Mississippi, the Coastal Marshes flooded by salt water from the Gulf itself and by fresh water from the land, and the Submerged Plains extend- ing into the Gulf, so that there is a submarine portion, as on the Atlantic coast. Under the waters of the Gulf, far out at sea, the submarine plain is ended by a comparatively abrupt declivity, where the Gulf bottom drops off from shallow into deep waters.

The Mississi]ipi Flood Plain starts at tlie foot of the great glacial deposits in Illinois, and at the Gulf end it expands into a great delta built into the Gulf by sediments brought down by the mighty river. This flood plain is usually well marked around

THE OZARK MOUNTAINS, 85

its outlines by high bluffs of loess. During glacial time the Gulf coastal plain seems to have been somewhat more depressed than at present, and the water of the glacier gathered into g, great basin which emptied into the Gulf. In this basin the rock-flour gi'ound by the mealing stones of vast glaciers was deposited as an exceedingly fine sediment. When the Laurentide Glacier was melting away into fragments in the far north, the laud rose again a little, and the Mississippi cut for itself a new channel, which was widened into a flood plain. The material into which the channel and the flood plain were cut was of glacial origin, and we call it loess; and thus the bluffs are of this formation. The Gulf region is rich with fields of corn, tobacco, and cotton.

In pre-Columbian times the entire region was a primeval for- est of giant trees and dense undergrowth entangled with vines. Into these forests aboriginal tribes penetrated to fish in the waters, to hunt on the land, and to cultivate little garden patches in corn and squashes. Here they built mounds on which their homes were erected; here they buried their dead in mortuary mounds; and here they constructed great tumuli upon whicli stood their council chambers, and where their ceremonies were held. On these artificial hills they established their tribal homes ; worshiped the sun, moon, and stars, and nuuiy animals ; organ- ized tribal governments of elaborate structure; and enforced laws that secured a high state of justice.

THE OZARIC MOUNTAINS.

Extending southward and westward from the Iron Moun- tains of Missouri far into Arkansas, there is an elevation of laud which we call the Ozark Mountains or Ozark region. This re- gion has an interesting though complex history. It is projierly divided into two districts. That north of Arkansas River has been a great plateau, and still retains many of the features of a plateau, but it is deeply trenched by numerous winding and complicated streams; and the reliefs or elevations whidi have been preserved have the structure of huge hills and small moun- tains, though a few of the forms are of more gigantic structure. Some of the greater elevations above the streains are in the Iron Mountain region, and others are called the Boston IMountains. The rocks are sometimes faulted, and the streams often follow fault lines. In the Boston Mountains the strata are chiefly hori-

86 PHYSIOGRAPHIC EEGIONS OF THE UNITED STATES.

zontal, and are deeply chauueled. On the south the rocks of this region in a general way bend down in a synclinal fold, and re- appear south of the river; below they are found strongly folded and sometimes faulted, and are eroded into long, i:)arallel moun- tain ridges with intervening valleys. Going southward, the ridges have a general east-and-west trend, but are often curi- ously carved and faulted. In the most southern portion of the region the streams are transverse to the rock structure. It would be well to call the northern district the Ozark Plateaus, and the southern district the Ozark Eanges.

THE GREAT PLAINS (PLATEAUS).

The region popularly known as the " Great Plains " is in fact a gi'eat group of elevated plateaus. They have therefore been colored as plateaus, and grouped in districts which are called plateaus. It would serve to harmonize the nomenclature if the name could be changed from 2)I(ih/s io jilateaKS. The zone in the United States extends from British America to the Rio Grande ; and the region extends far northwai'd in British America, and southward in the Republic of Mexico. Within the United States four districts are demarcated.

The Missouri district is deeply trenched by the upper Missis- sippi River and its great tributaries, in such a manner that the blocks to the north have their long axis extending from the northwest to the southeast, while the plateaus south of the river have their long axis extending from the southwest to the north- east. The principal streams of the region have their sources in the Stony Mountains, and eaiTy large volumes of water, while the local tributaries ai"e small. Along many of the smaller streams there are extensive areas minutely dissected by storm- water streams. Tbe rocks ai'e maiidy soft shales, so that corra- sion is rapid ; and the hills thus formed in the easily carved shales are naked and desolate, and hence are called had Icnicls.

In the district to the south, called the Platte Plateaus, the rivers flow mainly in an easterly direction ; and the trenches whicli they fomi divide the country into long ta])le-linids having the same direction. The ti-enehes are wider and shallower than in the north. The streams all join the Mississippi.

Going to the soutliward, the Arkansas Plateaus are found. The Arkansas, the Cimarron, and the two forks of Canadian

THK STONY MOUNTAINS. 87

River, drain the entire district, and separate it into long east- and-west plateaus. The trenches of the rivers are not very deep, but are usually very wide, and their summits are gi'eat treeless plains. All these rivers join the Mississippi soutli of the Ohio.

The fourth district is drained mainly by the Pecos, having a southerly direction ; but its eastern margin is drained by tribu- taries of Bed, Brazos, Nueces, and Colorado rivers of Texas. This is the Staked Plains, the region best adapted to the study of the four great laws of corrasion, which may he stated as follows : —

First, other things being equal, tlie rate of corrasion pro- gressively increases with the increase of the load Avhicli is the in- strument of corrasion ; second, other things being equal, vertical corrasion directly increases with the declivity of the stream; thh~d, other things being equal, lateral corrasion increases in- versely with the declivity of the stream, and vertical cori'asion is transmuted into lateral corrasion; J'omili, luaxiuaun corrasion is produced by maximum volume of water, maximum load, and minimum declivity, and the corrasion is lateral ; Jiftli, a stream heading in mountains, and crossing arid lands, is supplied with a great amount of sediment by frequent winds and occasional hard rains, and is caused to spread in a wide channel, so that the depth of water is greatly diminished, while the sand, having but a short distance to fall, is driven along by short excursions : so that the rate of corrasion diminishes in inverse proportion to the depth of the stream.

THE STONY MOUNTAINS.

The Stony Mountains constitute a well-marked gi'oup drained by the head waters of the Missouri on the east, and the head waters of Snake and Columbia rivers on the west. The name " Stony Mountains" was first given to this group, but was after- ward clianged to " Rocky Mountains," and then exti'uded indefi- nitely over other groui)s ; l)ut, as the group must be distinguished from others for physiograpiiic purposes, it seems well to return to the original designation. Theses mountains appear to be of very diverse structure. There are a number of great ranges; but they are not very systematically grouped, nnd have dift'erent directions because they are complicated with vulcanic moun- tains, plateaus, and hills. Some are carved out of broad anti- clinal folds, others are greatly faulted, and often sharp ridges

88 PHYSIOGRAPHIC REGIONS OF THE UNITED STATES.

appear; but the geologic history of the country has uot beeu so fully worked out that a eousisteut story of it can be given. The ranges are moderately high ; and, by reason of the northern alti- tude and a fair amount of rainfall, they are covered for many mouths •with snow, aud here many beautiful streams have their origin. The flanks of the mouutains aud high plateaus are often covered with great forests, and the low foothills with gnarled trees. The valleys are rich and productive, though mainly tree- less. Great mining industries are prosecuted, especially of gold and silver. In the heart of the gi-oup are the geysers and hot springs of the National Park, which has become a region of world-wide resort because of its wonders and its beauty.

THE TAKK 5I0UNTAINS.

In southern Wyoming, central Colorado, and northern New Mexico a great group of mouutains is found, whose lofty peaks are characterized by a wilderness of crags. The ranges are more irregular than those of the Stony Mouutains, and have a general north-and-south trend. Between the ranges there are great valleys, which are known as j)arJx-s. The four most important are the North, Middle, South, and San Luis parks; but there are others which almost vie with them in extent, and a gi'eat number of still smaller valleys, all of which are alike called parks. Above the timljcr line the peaks are naked ; below, on the flanks of the mountains, great forests stand, aud often spread over elevated plateaus ; while the valleys are beautiful prairies or parks. The ranges having a north-and-south direction are carved out of great anticlinal folds, but in each fold a zone of maximum curve is usually discovered on either flank ; so that the rocks at the flanks of the ranges are abruptly turned down, and extend under the parks, and are again tiirned abruptly above to a nearly horizontal jjositiou. Only fragments of these more horizontal beds above have been left : most of them have been degraded awaj'. The central portions of the ranges are in the main composed of metamorphic rocks of great age. This more irregular structure is modified to some extent by faults and various minor wriid^le?:. On the flanks of the mountains and out in the parks there are many beds of vulcanic rocks, which serve still further to modify the aspect of the ranges. In a few cases, especially on the western side, these vulcanic beds

COLUMBIA PLATEAUS. 89

have been piled up in mountain forms. On the eastern side there are a few outlying peaks of volcanic origin. Notable among these are the Spanish Peaks. The gi-oup terminates to the south in the neighborhood of Santa Fe. The head waters of Platte, Arkansas, and Canadian rivers drain the mountains on the east; to the west they are di-ained by the head waters of Colorado River, which empties into the Gulf of California ; while to the south they are di-ained by the Rio Grande del Norte. This is a land of ranges and valleys, of peaks and parks, of naked crags, forest-clad mountains, and plateaus.

There are features extending along the entire length of the gi'oup from north to soiitli on the eastern side, and again irreg- ularly on the western side, that give rise to many small and pic- turesque parks sometimes called gardens. It has already been explained that the rocks of later age are turned up sharply on the flanks of the mountains as sandstones, shakis, and lime- stones of many colors, often of bright-red hues, while beds of alabaster are found. The rocks stand on edge. The softer beds are worn out, and the harder beds remain standing as great walls ; so that many beautiful garden valleys are produced, par- allel to the gi-eat ranges, and separating them from the plains below. The forms of these rocks are often varied and majestic, and sometimes fantastic. The Garden of the Gods, near Pike's Peak, is one of these valleys, which has become a favorite visit- ing place from the adjoining summer resorts.

COLUMBU PLATEAUS.

To the west of the Stony Mountains stretches a great plateau region which is di'ained into the Pacific by tributaries of Colum- bia River. It is a complex of plateaus of diastrophic and vul- canic origin, relieved by a few great mountains, and having many beautiful valleys. The highlands are covered with for- ests; the lowlands are naked.

In Cretaceous time the region had many extensive plains, broad valleys, high mountains, and some portions were covered by the sea. The mountains were mainly of granite, quartzite, and mica schist, with rocks of later age on their flanks.

In Eocene time extensive diastrophism prevailed, and with it came vulcanic activity, by which a number of great mountain cones were erected.

90 PHYSIOGKAPHIC llEGIONS OF THE UNITED STATES.

Ill Neooeue time the lavas were more fluid, and broke out in many new places, pouring out thin coulees, frequently filling or obstructing valleys. These later eruptions continued for a long time, upbuilding the region by burying the old topogi-aphy and piling the lavas against the mountains. In the process, valleys were often dammed by floods of cooling lavas, and behind these obstructions many lakes were formed. Since vulcanism has ceased, many of these lakes have l)een drained, and the old lake beds are now rich agricultural lands. In many places the ancient mountain summits yet appear, but about them are scattered great irregular vulcanic jilateaus. Small valleys have sometimes been carved, but often the streams have cut narrow trenches which are canyons. Frequently the canyon walls are composed of lavas, sometimes with interbedded lake beds. In the old mountain regions gold and silver ai'e mined, and in many places the gi'avels left in the valleys and canyons below have much gold in nuggets, flakes, and dust, which gives rise to placer min- ing. Snake Elver runs for several hundreds of miles of its course through a canyon carved in the lavas. The walls of the canyon are often precipitous, effectually barring cross-river transit. In places late coulees have dammed the river ; Shoshone Falls are formed in this manner. Here a mad torrent of water plunges over a gi-eat lava dam in a cataract of gi'andeur.

COLORADO PLATEAUS.

During the Cretaceous period a shallow sea spread over the region of the Colorado Plateaus. This great enibayment of the ocean stretched far to the east, northeast, and southeast, and its oriental margin was a little east of where the Mississippi River now runs. In the midst of this sea there was a great archipel- ago where now the Park Mountains stand. In late Cretaceous and early Eocene time the entire sea was slowly upheaved, and the waters retreated. The upheaval was very irregular, and gi'eat diastfoiihic basins were formed, in which the fivsh waters accumulated, and it thus became a gi'eat lake region. For a long time the waters were brackish, as the lakes evaporated to such an extent that only small channels were cut, such being sufficient to bear away the wat(>r not evaporated. In a broad way the upheaval in the eastern region was by gentle flexures ; in the western region it was chiefly by faults. As the fresh-

COLOKADO PLATEAUS. 91

water basins were many and large, and the land areas compar- atively small, the dry lands were washed down into the Great Lakes ; but elevation proceeded faster than degi-adation, and the lands grew both by upheaval and by the enlargement of their borders through deposition, or, as it is sometimes called, aggra- dation. The slow ui^heaval continued through Eocene time. Tlie western half became highly differentiated from the eastern half, as at the west diastrophism was more energetic, and at the same time vuleanism was inaugurated on a gi-eat scale. In the plateau region, which we now have under consideration, the dias- trophism was chiefly by faults and monoclinal flexures, and the whole country was Itrokeu into gi'eat irregular blocks, mainly by lines having a general east-and-west direction, but in the soutlieast a north-and-south direction. At the north the blocks were tilted to the north, but there were many minor variations, and in the south they were tilted to the east. The blocks thus produced are the gi'eat plateaus, which were modified and dis- sected by rains and rivers. At the time when these movements began, the rocks immediately beneath the sea were lying in a horizontal position to a depth of many thousands of feet. When the land was thus upheaved in tilted blocks, tlio strata were slightly inclined; and the streams heading in the blocks tilted northward mainly ran northward, with branches from the east and west, and for a long time were gathered into lakes that drained into Colorado Eiver, while in the south they drained chiefly east and south into the Eio Grande del Norte. As general upheaval went on, all the lakes were drained by the cutting of outlet channels, and the whole region became arid. All this was in early Neocene time. At last, in late Neocene time, the diastrophic blocks were trenched ; and when the lakes were drained, their bottoms became valleys, and the valleys were then slightly trenched by streams running into the Colorado and Rio Grande del Norte. Thus plateaus of great diastrophic blocks were dissected by a vast network of streams. The up- turned edges of the blocks were degraded by sapping, — a pro- cess which was described in a former monogi-aph, — and dias- trophic cliffs were carried back in great steps or teiTaces. In this manner the plateaus were still further dissected, so that the whole region is now a vast assemblage of great plateaus, divided into smaller plateaus by the channels of streams, and still fur- ther divided by cliff's produced by sapping. In general the entire

92 PHYSIOGIUPHIC KEGIONS OF THE UNITED STATES.

region is a group of tilted blocks, whose higher edges termiuate in gi-eat cliffs formed by sapping. There are a few cliffs which have not retreated far, and still mark the site of the faults ; while there are other great plateau edges which are nionoclinal flex- ures, and here the bent rocks yet appear. The great cliffs are everywhei'e adamantine structures of magnificence: they are terraced and buttressed, and cut with deep reentering angles, and often set with towers, pinnacles, and minarets; they ob- struct the traveler even more than mountain ranges; in fact, from the plain below, they apjiear as mountains built of naked rock. Where the rocks are limestones and hard sandstones, bold precipices are formed ; but between these steep ledges the softer shales are often carved into a filigree of fantastic forms. A facade thus constructed of rocks of varying hardness in bands of many colors, in forms that resemble Titanic architecture, makes the scenerj^ a constant wonder to the traveler. Where the edges of the plateaus are nionoclinal folds, thc^ inclined rocks are carved on another plan, giving variety to the scenery.

The streams usually have deep channels. Little rills born of showers and <lying with the sunshine have often cut deep but narrow, winding gorges, at the bottom of which great caves are often foTind. The creeks have cut larger canyons, and the rivers have cut mighty canyons, — gorges sometimes hundreds of miles in length. So there are canyons along the rivers, smaller canyons along the creeks, still smaller canyons along the brooks, and pictui'esque canyons along the wet-weather rills; and tlie plateaus are thus divided by a lab3'riuth of deep gorges. While the diastrophism of the blocks has produced gi'eat plateaus, and while stream cutting and stream sapping have been dissecting them, vuleanism has been in progress ; and old volcanoes are often, found on the summits of the plateaus, and cinder cones are scattered in many places, and great sheets of lava have been poured out that have become the caps of table mountains, and other sheets have been piled one upon another so as to constitute imbricated mountains, and in a few places laccolitic mountains are found. Thus with cliffs, can- yons, gorges, and volcanic mountains, the entire region is one of picturesque grandeur.

To the north there is a plateau known as the Uinta Moun- tains, having its greatest length in an east-and-west direction. It has a mouoclinal flexure on each flank, — one at the north

COLOKADO PLATEAUS. 93

and one at the south. Between these abrupt flexures the rocks are gently carved. Like many other of the phiteaus, the south- ern edge was upheaved much more than the northern edge. This plateau was dry land during a part of Cretaceous time, and there were islands here during Eocene time. In Neocene time the entire plateau became dry land, and from that time on, the rate of upheaval was comparatively great, and through this range great lakes to the north were drained into lakes farther south. So the upheaval went on as the plateau was lifted ; but the river was able to carve its way through the plateau, and still remained an outlet for the upper lakes during all Neocene time. In this period it was upheaved more than twenty thousand feet, yet the river cut its channel and preserved its course during all the time. The river came from the north, and impinged on this block about halfway in its course from east to west, then made its way into the heart of the block, next tui-ned eastward for sixty miles, and finally turned again to the southwest, until it left the block at its southern margin. So the canyon was cut through a bluff that was slowly lifted by forces from below.

The small streams have all trenched deep gorges, between which minor plateaus are found ; and sometimes the trenching has left behind gi-eat peaks, so that the plateau has received the name "Uinta Mountains." It is largely covered with forests, but the deep gorges often have cliffs of naked rock.

In the southeast there is a great plateau, on the western side of the Rio Grande del Norte, opposite the Santa Fe Plateau. The block is about eighty miles square. It was upheaved from the west side along a line which presents a general north-and-south direction. It was not faulted, but upheaved in monoclinal flex- ure, bringing up the Neocene rocks, Cretaceous rocks, Juratrias rocks, and Carboniferous rocks. The Cai'boniferous rested un- conformably on granite, and the gi'anite also was brought up to an altitude several thousand feet above the little valleys on the west. Looking at the edge of this plateau from the west, it ap- pears to be a great range of mountains. The block itself was tilted eastward and to a sliglit extent southward. As it came up, the Eocene, Cretaceous, and Juratrias rocks were all washed away from the western margin of the plateau, leaving a summit of granite ; but going eastward, rocks of all of these ages appejir in order from the older to the younger. As the block was tilted, there was very little vulcanism on its western flank, but on the

94 PHYSIOGiUrHIC KEGIONS OF THE UNITED STATES.

east vast bodies of lava and ashes were poured out, so that on this eastern margin of the block great volcanoes were erected. The emission of matter from below was accomplished to an im- usual extent by explosion, so that vast quantities of ashes were ejected, and these blew over the plateau, and thus beds of ashes scores and hundreds of feet in thickness were formed. As the volcanoes and ash beds were constructed, the main trend of the drainage was turned southward through Jemez River and its tributaries by a ramifying system of streams from the north, east, and west. Tliese streams have often carved deep, narrow canyons, that reveal the structure of the vulcanic rocks above, and the sedimentary rocks below. Space forbids the further description of this lieautiful plateau, ^"itli its granite range on the west, its volcanic peaks on the east and north, its beautiful valleys among the dead volcanoes; with deep gorges through which streams run, and hot springs that flow from the vulcanic rocks, and curious little faults that appear here and there, and strange forms that have been produced by corrasion, and lakes that have been filled and di'ained, and the forests with which the plateau is crowned.

To the south the San Francisco Plateau is found, — a table- land of gi-eat extent. It was upheaved as a block from south of west, and tilted to the east. All the Eocene and Cretaceous rocks have been washed away from its summit, and are found only on its flanks; but portions of the Juratrias remain. Through Eocene time it was deeply trenched by many streams. In Neocene time vulcauism prevailed, and a great system of vol- canoes was built, and many cinder cones are found ; often old channels were fiUed with lava, cinders, and ashes. The plateau is quite elevated, and the rainfall is nearly twenty inches an- nually; but the waters thus falling on the surface sink away into the lavas, cinders, and ashes, and are gathered below at a great depth in the old stream channels. Sometimes these under- ground waters excavate great caves below, and then the upper rocks fall in, so that many sinks are formed. In one of the cinder cones a crater lake is found, and scattered over the pla- teaus are many wonders. It is covered with a great forest, with intervening prairies that are gardens of wild flowers in mid- summer.

Only three of the plateaus of the great number are described, but they sei've as types for the entire region.

THE BASIN KA.NGES. 95

THE BASEST RANGES.

South of the Columbia Plateaus, and west and south of the Colorado Plateaus, is the great region of the Basin Ranges, extend- ing far down into Mexico. It is a region of isolated diastrophic ranges, usually having a noi-th-and-south direction, and often complicated with vulcanism. The blocks out of which the ranges are carved are uplifted abruptly, mainly by faults, l^ut occasionally by steep monocliual flexures, so that the rocks usu- ally dip gently away to the other side. These simple diastrophic blocks are often greatly modified by vulcanism, and the lava from below is often piled up in peaks and small plateaus, while occasionally volcanic cones are found. The mountains arc never high, and are often destitute of large trees, and sometimes are mountain deserts. Between these isolated ranges there ai"e broad valleys with small branches extending into the mountains. The great valleys below are diastrophic basins which receive the sands and gravels washed down from the mountains, and are filled to the present surface from great depths Itelow. In the mountains themselves narrow valleys have been trenched. Down these the streams flow until they are lost in the sands, so that their waters are not carried to the sea. Sometimes there are salt lakes in the valleys. Of these. Great Salt Lake and Pyramid Lake are the more important examples. In early Pleistocene time there were many njore lakes of this character ; and, as the climate was more humid, some of them, at least, found outlets to the sea.

The region is naturally divided by the Colorado River of the West. The district to the north is characterized mainly by closed basins, though near the Pacific Ocean there are many filled valleys which drain directly into the sea, and near the Colorado thei'e are few. Southeast of the river all the basins have wet-weather drainage channels into the great river itself and the Gulf of California, or into the Rio Grande del Norte and Gulf of Mexico. The entire region is arid, usually having less than ten inches of rainfall annually over the filled basins. It is the desert region of tlie United States. The region east of the Colorado may ultimately be distinguished by another name: " Sierra Madre" would be appropriate. The mountains are more diverse, and the valleys more deeply trenched.

96 PHYSIOGRAI'HIC UEGIONS OF THE UNITED STATES.

PACIFIC MOUNTAINS.

This is a great gi'oiip of mouutaius and intervening valleys. The Cascade region is a diastrophic plateau on which vulcanic plateaus have been piled, aud on them great volcanoes were ele- vated which are now extinct. The most picturesque peaks in the United States south of Alaska are here found, and in their gorges glaciers yet remain. From the crater of one of the vol- canoes in Oregon there have been vast exjjlosions, by which ashes and cinders were scattered widely over the adjacent country, and afterward the rocks about the crater fell into the depths below. The basin thus made has been deeply filled by snows aud rains, and a lake has been formed of gi'eat extent and depth, known as Crater Lake. To the west of these mountains a river flows northward into the Colum])ia. The upper part of the valley is comparatively narrow ; but along the lower two thirds there is a broad stretch known as the Souud Valley, which is formed by the upheaval of the Cascades on the east, and of the mountains near the coast on the west. At oue time an arm of the sea extended up this valley in a great gulf, and since that time the land has been somewhat uplifted. It is thus a constructed val- ley between mountain ranges, and has been partly filled with sediment. To the west the Olympic Mountains stand on the north of the Columbia. The structure of these mountains is un- known. South of the Columbia, near the coast, are the Oregon Mountains, often called the Oregon Coast Ranges.

South of the Sound Valley aud the Oregon Ranges there is a very irregular group of mountains, drained in part to the Co- lumbia, iu part to the Sacramento, but in chief part directly into the ocean. It is an upheaved archipelago kuown as the Klamath Mountains. South of the Cascade Range stand the Sierra Nevada. It is a great block upheaved from its eastern margin, and tilted westward. The displacement is by a complicated system of faults and folds, along which there has been much vulcanic action; and the coulees of lava have often obstructed the valleys, and formed lakes which have sometimes been filled by sediments until they were di-ained away. One of these streams, Ti-uckee River, has its source far back in the block. In late Pleistocene time a series of coulees poured across it, and built a dam many hundreds of feet high, behind which Tahoe Lake has

rACU'IC MOINTAIXS. 1)7

been gathered, until now it runs over the dam, in which it lias cut a small channel. Elsewhere in the Sierra there are other lakes having internsting histories. As the l)lock tilted we.stwanl, the drainage is chiefly in that direction. The irrt'gular streams have carved out many flaring, steep gorges, between which moun- tain ridges stand, diminishing in altitude to the vidh-y of ( ah- t'ornia. Along the western flank there has been much vuh-an- ism; and the coulees have formed many plateaus which have been trenched by the streams.

To the west of the valley stand the North and South Coast ranges, which are mainly anticlinal folds, sometimes compressed and faulted, and very nuK-li broken into fragments. These coast ranges are severed where the San Joaquin joins the Saci-ameuto and flows through the Golden Cltite into the ocean. The bays about San Francisco are diastrophic basins modified by gradiv tion. The valley of ("alifornia is naturally divided into two parts, — the northern valley, drained l)y the Sacramento; the southern, by the San Joac^uin. They are naturally treeless, gently rising to the mountains on either side. Not long ago geologically the sea occupied these valleys as a great gulf; but they liave since been upheaved, drained, and covei'ed with a deep accumulation of clay and sand washed from the mountains.

The scenery of the Pacific mountain region is greatly diversi- fied, and has manj^ contrasting f(>atur(>s. Tlie extinct volcano(>s of the Cascade Range have towering peaks that are covered with snow during many months, whose glittering crowns, revejded through vistas of forest land or seen from the far-away ocean, ever inspire delight. With green forests below, gray slopes above the forests, and peaks of silver, their symmetry is won- derful. This aspect of the mountains entirely changes as the mountaineer ascends from valley to mountain height; then the wooded slopes are transformed into deep gorgi's covered with evergreen forests of giant trees; the gi'ay zone above is trans- formed into crags, towei's, and minarets of many but f|uiet colors; while above is the zone of silver, with its snows and glaciers. So the mountains are in uniform, — green, gray, ami silver, — all resplendent in noonday sun. When tiie clouils come, the peaks are masked; but as they vanish or roll away, a chan- ging panorama of splendor is presented.

The Sound Valley is mainly covenvl with forests of trees, tall and statelv. Amonii' the v(>nerable ffiants vounger generations

STATE NORMALSOHOOL.

\_'

L' ■	r.EtiF.SI': —	\	^M
J/ou.	Uiina are calufil Huff	%JI
FMr	tut ■■ ■• Blue		SW/
Plain	K ■■ ■■ Ortrri	V^
v:'	w
		•

loo ruv.sKxiKAi'iiu i;i:(ii()Ns or the vniteu states.

live; ami pines, lioinlocks, and cedars lift their bourgeoning heads to vie with tlieir elders. On the gronnd dead and pros- trate trunks lie, while others recline against the living. Among the dead and living trees tliere is an elaborate interlacing of vines, creeping, climbing, twisting, and weaving a woof of \ine in a warp of branches. Over the mountains to the west these forests extend, losing but little of their luxuriance.

Descending from ilount Sliasta into the valley of the Sacra- mento, the uortiiern end of the great valley of California, cinder cones are seen in great numbers. On these cones tlie rains and snows fall and sink away, to reappear far away in great springs. Then the tributai'ies of tlie Sacramento roll down in deep gorges. On the eastern side, and on to the south for five hundred miles, stretches the great Sierra Nevada, with toweriug, irregular, and dunisy moimtains on its eastern margin, cold, gray, and deso- late. It is a region of gorges and peaks, but at their feet there are many beautiful lakes with clear emerald waters. Below the peaks is a region of forest. The traveler, in descending west- ward to the valley, passes from a zone where forests are low and gnarled by storms, until gradually the trees become more stately, and he reaches the groves of sequoias, — the great trees of the world, whose mighty forms record the history of many centuries of winters and summers. In the v;dley below, live- oaks are found with branches akimlio, and knotted fists ready for pugilistic fray.

Beyond the valley are the Coast Ranges, where the balm of the tro])ics loathes the winter with verdure, and boreal zones lioon the snniiiK-r with zephyrs.

The Kockv Mdcntaixs. — In an inipnrtaiit sense all tlio mountains west of l)ii' (iveat I'latenns constitute a single group, though the regions into wliii-h they are diviileil are phiinlyileinarcated. There is great diversity, ami all known types are found; and there are large areas of jdateaus and still larger areas of valleys ; yet for some purposes it is convenient to use a general term for them all. For this purpose two names have been used. — " Koeky Mountains'' and "Cordilleras." The term " Rocky Mountains " has sometimes been applied to the entire group of groups, both by writers ami in popuhir s)ieech. It has oftener been applied in a vague way to the Stony Mountains, the Park Mcumtains, the Columbia Plateaus, the CoUu'ado Plateaus, and a part of the Hasin Ranges, especially the southern district, or Sierra Madrc. The term " Cordil- liras " has been used by a few writers to cover the same region, but (lopular usage is confined mainly to the term •• Rocky Mountains."' This name has liecn useil in this broader sense to cover the entire region by the officers of the general government, and has been woven into the federal laws with this meaning; so that official and popular usage coincide. For many years it has liccii used with this signi(ii-ani-e by the presi'ut writiT.

PRESENT AND EXTINCT LAKES OF NEVADA.

By Israel C. Russell.

TOPOGKAPHY AND CLIMATE OF NEVADA.

The traveler who crosses the State of Nevada ou the Central Pacific Railroad will observe that for miich of the way the route follows the Humboldt River and crosses the " grain of the coun- try." The mountain ranges trend northeast and southwest, and are separated by level-floored valleys. The valley of the Hum- boldt, however, is a striking exception to this rule. The river rises on the eastern border of the State, and flows westward for half its length before conforming with the direction of the mountain ranges. At many localities the traveler can see far off over the desert valleys to the right and left of his course,

- and cannot fail to be impressed with the fact that the dei)res- sioiis between the sharp, narrow ranges were formerly nuich deeper than now, and have been filled in or gi-aded up, as it were, to approximately the same level.

Could the traveler scale one of the higher peaks that he

, passes, and obtain a wide-reaching view over the i-iiggcd land, the fact that the depressions Ijetween the nKuuitain ranges have been partly filled would become more apparent. In general, the central parts of the valleys are level-floored; but at their borders the material with which they are filled slopes upward, and rests against the rocky sides of the inclosing mountains. The sculpturing of the mountains, and the abrui)t manner in which theii- precipitous sides frequently plunge down to meet the alluvium in the valleys, indicnte the de])t]i to which their bases have become buried. Borings through the soft deposits

(CopjTiglit, 1895, by Ameriean Book Company.) 101

10- PRESENT AND EXTINCT LAKES OF NEVADA.

iu the valleys show that their rocky bottoms are frequently at least two thousand feet below the present surface. Careful estimates based on the character of the mountain slopes, and on borings not only in Nevada Ijiit over a much larger i-egion of which that State forms a typical part, indicate that iu many instances the depressions between the mountains have been filled to a depth of at least foiu- or five thousand feet.

Dirt and stones have beeu washed from the mountains into the adjacent valleys, and graduallj' reduced the inequalities of the surface, but still the topogi-aphy remains exceedingly rugged. The sharp, angular mountains frequently I'ise from four to six thousand feet above the neighboring valleys. The coarser mate- nal, as well as much of the finer debris washed from the uplands, has beeu deposited about the mouths of the gorges through which it descended, and forms broad alluvial cones. The accumula- tions about the entrances of adjacent canyons are frequently confluent, and form a pediment for the angular peaks that seem to rest on them. The margins of each alluvial-filled basin slope down in gentle curves convex to the sky, and mei'ge into the broad level area in the central part of the depression. When the openings between adjacent valleys are wide, the matenals iu their bottoms are imited in such a manner as to form a single plain, thi'ough which the higher summits of the partially buried ranges project, and form island-like elevations known as lost moiuitahti.

The topogi'aphy is strikingly at variance with that of regions having an al )undant and well-developed drainage. Many of the valley bottoms are micut by stream channels, and are so inclosed by mountains that they would hold bi'oad lakes before being filled to overflowing. Scores, if not Inmdreds, of such basins exist, but lakes are rare.

The traveler who visits Nevada will be impressed also with the arid and frequently decidedly desert character of the coun- try. Forests are absent, excejit in a few limited areas on the higher mountains. One may ride for hundreds of miles through the valleys without finding a tree to shelter him from the in- tense heat of the summer sun. The prevailing vegetation is the sagebrush {Artemisia). This, with other desert shrubs, imparts a gray tint to the russet brown of the naked land. For months together not a drop of rain falls, and for weeks in succession the sky is without a cloud.

TOPOGKAPHY AND CLIMATE OF NEVADA. 103

Uu the raiii charts recently issued by the U. S. Weather Bureau, the rainfall of Nevada during the three mouths of spring, with the exception of a small area at the north, is below ten iuches, and over a considerable portion of the west- central part is less than one inch. In summer it is less than one inch, and in fall and winter less than three iuches, for the entire Htate. The precipitation for the year is represented as being less than ten inches, and over a large area in the west- central part is below five inches. The obsei-vatious on which these generalizations are based were made from the early settle- ment of the country to the close of 1891, principally along the railroads, and do not show the depth of precipitation on the mountains. They fail to some degree, also, in expressing the extreme aridity of some of the valleys in the western and cen- tral jKU'ts of the 8tate, for the reason that at times, as I have been informed by settlers, there is no rain at all in those regions during eighteen or more consecutive months.

In contrast with the exceedingly arid character of Nevada, I may recall, for the sake of illustrating by contrast, the fact that in the Mississippi Valley the mean annual precipitation is from 30 to 40 inches, increasing southward to 50 or (iO inches. In portions of Florida and on the coast of North Carolina it exceeds 60 inches, and on the coast of the State of Washingtou is more than 100 inches.

One other series of facts in the jihysiography of Nevada should be borne in mind by the student who wishes to know the life history of her lakes.

The small rainfall and clear skies are accompanied by a high mean annual temperature. The humidity of the titmosjjhere is low, aud evaporation excessive. The annual loss by evaporation from a surface of standing water exposed to the sun and winds ranges from 70 to more than 100 inches. On a given area in the valleys the amount of water that could be evaporated annually is from 20 to 80, and in exceptional years 100, times the meau annual precipitation.

The marked diversity in the relief of the land, and the char- acter of the climate, determine the principal episodes in the his- tories of the lakes to which attcMition is here invited.

Many of the valleys are 1)road aud deep. Under more favor- able climatic conditions, they would be transformed into exten- sive lakes, but at present arc! without standing water throughout

104 PRESENT AXD EXTINCT LAKES OF NEVADA.

the year. The deep porous soil acts like a spouge, and is capable of retaiuiug much more water than the clouds now furnish.

There is a second som-ce, however, from which the desert valleys derive water, that must not be ignored.

The long parallel mountain ranges are, as a lode, steep on one side, and slope much more gently iu the opposite direction. Each of these sharji, narrow ranges is the upturned edge of a block of the earth crust, separated from the adjacent block by profound fractui-es. The fractui'e which permitted this unequal tilting commonly follows the base of the steeper side of a range, while the depressed border of the fractm-e underlies a partly filled valley. This " basin range stnicture " is shown in the ac-

iMke Range. Winn<-mnrrn -Vafhe Roiioc

Piiramul jk^,^ " »'nemucca

'L<ih(. j^ Lnh,

jri.-(.

Ideal Section through Pyramid and Winnemucca Lakes, Nevada.

companj'ing generalized section. The breaks refeired to fre- quently admit of the escape of water from soiu'ces deep below the sm'face, and copious sj^riugs result. In many instances the water flowing from these fissures is highly heated, showing that it rises from such a depth that its temperature is raised on account of the general interior heat of the earth, or else that the walls of the fis- sure have undergone recent movement, and by their friction ele- vated the temperature. These fissure springs are fed by the rain falling on distant regions, no one kiidws where, and furnish an im- portant adjunct to the meager rainfall in the region where they rise. Much of Nevada would be impassable in summer were it not for the waters that reach tlie desert valley through fractures iu their bottoms. The spring waters bring with them large quantities of mineral matter in solution, which is added to the lakes to which they may become tributaiy, or, when evaporated from the adjacent surfaces, appeal's as a white, saline incrustation.

THE PRESENT L.VKES.

The nature of the topogi-aphy of Nevada, and the character of the climate, lead to the formation of two classes of water bodies. These may for convenience be designated as ephemeral lakes and perennial lakes. The former are especially character-

EPHEMEKAL LAKES. lUd

istic of the vast arid region of which Nevada is a typical part, and merit theii" name because of their brief existence; the latter hold their autonomy for many consecutive years, and even for centmies, and are fresh or saline according as they ovei"flow or are completely landlocked.

Ephemekax, Lakes. — Could one be so situated as to obtain a bird's-eye view of Nevada, and watch the coming and going of the seasons, the manner in which many lakes are liorn in the desert valleys, live their l^rief lives, and pass away, would appear like the changing views in a panorama.

When the clouds gather in dark, gloomy masses aboiit the mountain tops, and gradually expand until they bridge over the intervening basins, the rain falling from them descends most abundantly on the uplands, and in less quantity on the parched valleys. Sti'eams fed .by the falling raindrops course down the mountains, washing away the loose material that frecjiiently clogs their channels, and reach the valleys heavily loaded with silt, and not infrequently roll along bowlders many tons in weight. These roaring torrents sometimes disappear beneath the surface on reaching the border of a valley, and add their loads to the deposits left by previous floods. The water that thus disappears emerges again when the subsoil becomes sat- urated, and gathers in the lowest depressions. The streams that are- not wholly al)Sorbed by the porous alluvium flow on with diminished volume in bifurcating chaiuiels, and, tojivtlicr with the rain that falls in the valley, finally spread out and form shallow lakes. Should the storm continue, the sheets of water in the valleys will expand, and possibly become many square miles in area. Such lakes are always shallow, and always yellow with mud in suspension. When the sun breaks through the storm clouds, evaporation becomes active, and the lakes gi'ad- ually contract their boundaries, and perhaps in a few lioui-s or in a few days are entirely dissipated. When the water has dis- appeared, absolutely barren mud plains remain, which harden under the sun's heat, and become cracked in all directions as their surface contracts in drying. The lake beds then have a striking resemblance to tessellated pavements of cream-colorcnl marble, and soon become so hard that they ring beneath the hoof beats of a galloping horse, but retain scarcely a trace of his foot- prints.

Such bare, level mud plains are characteristic features of the

lOG PRESENT AND EXTINCT LAKES OF NEVADA.

greater part of the valleys of Nevada, and are known iu Mexico aud adjacent portions of the United States as^^/rty/o.^. The lakes to which they owe their origin are termed plai/a lakes.

These ephemeral water bodies frequently come aud go almost as erratically as the shadows of the clouds cast on their own tawny surfaces. In other iustauces lakes of the same type appear during the winter months, and remain until the heat of summer reaches a maximum ; they then give place to smooth plains of mud of the same character as those left by^the more transient water sheets. Still other playa lakes are for a time pereunial, and only evaporate to dryness diu-ing seasons of imusual aridity. The playa lakes with long periods of oscilla- tion approach the condition of the lakes which have ne^^er been knowu to become dry. Ephemeral aud perennial water bodies are thus united in one series. Thei'e is no I'igid Ijoundary be- tween them; but it is convenient to select well-marked tj-pes to stand as representations of the two extremes, just as the naturalist does when he di"vidcs animals into genera.

Lakes of the Black Bock and Smoke Ceeek Desekts. — The largest ephemeral lake of Nevada is foimed during winter months on what is knowu as Black Rock Desert in the north- western part of the State (see Plate I.). This desert valley is irregular in shape, and has lateral valleys opening from it. Its length from northeast to southwest is over one hundred miles, aud its average breadth twelve or fifteen miles. In summer it is almost entirely without tributary streams, except such as are fed by hot springs. In winter many brooks descend the mountains to the east and west; and the channel of Quinn River, which enters the basin from the northeast, is transformed into a veri- table river. The course of this stream in summer is marked only by a diy channel, with an occasional water hole; but in winter it is flooded so as frequently to be impassable to a man on horseback, aud has a length of upward of a hundred miles. Its watei-s then spread out on Black Rock Desert, and at times form a long uaiTow lake from 450 to 500 square miles in area. Although seldom over a few inches deep, it is impassable on account of the softness of the mud forming its bottom. Many times the "lake" is a vast sheet of liquid mud, and for this reason is knowu as "Mud Lake" by the settlers of the region. This name is not distinctive, however, as many other playas have the same name attached to them.

SEMIPEUENNIAX LAKES OF CAKSON DESERT. 107

Black Eock Desert is uot closed at its southern eutl, but opens out iuto another deep basin, known as Smoke Creek Desert. At the place of union, rocky headlands project from the mountains on the east and west, and approach within about five miles of one another. Where this constriction occurs, tliere is a slight rise in the valley bottom, but sufficient to divide the water that enters the basin and leads to the formation of two lakes. The lake formed during the winter on Smoke ('reck Desert is not as large as its companion to the north, Init is sometimes 25 to 30 miles long and 5 miles wide. In all of its essential featui-es it is a counterpart of the one just described.

The winter lakes on Black Eock and Smoke Creek deserts, as in many other similar instances, do not occupy the entire valley bottom, but are suri-ounded by a broad fringe of what to the eye appeai-s level land. This l)roadening tract is covered with sagebrush and other desert shrubs. In early spring many flowers beautify the ground, and fill the air with a faint pei-fume. The playas left by the desiccation of the lakes, however, are always barren. Not a plant takes root in their baked and har- dened surfaces. Where these mud plains meet the surrounding areas clothed with desert shrubs, there is often a belt of ground that is soft and marshy in winter, and frequently retains something of this character after the lakes have disap{)eared. In summer it Ijecomes white with salts brought from below )»y ascending water, and left on the surface when evaporation takes place. These efflorescent deposits become unusually alauidaut about some of the hot springs, and are then apt to contain borax in addition to the sulphate and carl)onate of soda, common salt, etc., which make uji the bulk of such incrustations.

Lakes of Carson Desert. — The Carson Desert in west-cen- tral Nevada, shown on the niaj) forming Plat(> T., is a l)asin sur- rounded by irregular mountains. Its length from northeast to southwest is about 75 and its width 25 miles. It receives the waters of Carson and Humboldt rivers, but has no channel of escape. Both of these streams are Avorthy to rank among rivei's, if their length and volume in the winter season are alone con- sidered.

Carson Eiver rises on the eastern slope of the Si(>rra Nevada, and has a length of 125 miles and a tlrainage area of about 1,000 square miles. Humboldt Eiver is fully 300 miles long, and drains a region of small rainfall, in wliicli the divides are frequently

108 PRESENT .VND EXTINCT LAICES OF NEVADA.

indistiuguisliable. The area of its hydrographie basiu may be variously estimated, but is iu the ueighborhood of 7,000 or 8,000 square mUes. This is the largest stream that has its source iu the central area of the arid region of which Nevada forms a typical part, and is abnormal iu several particulars. Each of these streams is exceedingly variable in volume. In winter they carry several hundred, in the case of the Carson River fifteen hundred, times as much water as during the average summer stage.

The waters of the Carsou and Humljoldt spread out on the Carson Desert, and ai-e there evaporated. When flooded, they form two sheets of water, known as North Carson and South Carson lakes. These lakes are frequently designated as "The Sink of the Humboldt" or " Humboldt Sink," and " The Sink of the Carson ; " the popular beUef being that the waters escape by subterranean outlets, or sink below the sm-face. This is not the case, however, as it can be proven that the infloAv is counterbal- anced solely Ijy evaporation. North Carsou and South Carson lakes are of the playa type, but are more persistent than the lakes of Black Rock and Smoke Creek deserts. They some- times hold their integrity for a succession of years, but evap- orate to drjTiess during seasons of more than usual aridity. North Carson Lake is rudely elliptical in outline, and is from 20 to 25 miles across from east to west, and about 14 miles broad from north to south. That its depth is never over a few feet, has been shown by examining its bed when dry.

South Carson Lake, when at its maxinuim as known in recent years, is from 4 to 5 miles in diameter, and aliout 4 feet deep. Its depth is unusual for a playa lake; and for this reason, and because its feeding stream rises iu high mountains, it is more constant than many other examples of its class.

Variations in the extent of the lakes of the Carsou Desert have been more marked in recent years than formerly, for the reason that the streams supi^lying them are being used for irri- gation. They are now more apt to become dry, and pass to the condition of playas during the summer, than when first known to the settlers of the region. They still serve, however, to show the connection that exists lietween the ephemeral lakes born of a single shower, and evaporated to drjniess after a day or two of sunshine, and perennial water bodies that eudm-e for a term of years.

SEMIPEKENNIAL LAKES OF EASTEKX XEVADA. 109

LaivES of OTHER INCLOSED Basins. — Diamond valley, to the north of Eureka, furnishes another example of the manner in which a delicate balance between precipitation and evapora- tion leads to striking changes in the aspect of an inclosed basin. In summer this valley is exceedingly desolate, and a part of its area is white with salt. In winter the streams from the sur- rounding mountains are revived, evaporation decreases, and a lake is formed in the lower part of the depression. The previously precipitated salts which give the desert something of a wintry aspect during months of excessive dryness, are dissolved, and a lake similar in appearance to the normal lakes of humid regions appears in its place. Year after year this fluctuation goes on, and the appearance of the valley changes in sympathy with the iinseen forces that control tem])erature and humidity.-

In the central part of the area of interior drainage between the Sierra Nevada and Wasatch Mountains, there rises a con- spicuous range known as the East Humboldt Mountains. These are snow-capped in winter, and repeat on a smaller scale many of the conditions resiilting from the gi'eat elevation of tli<' nu)un- tains bordering Nevada on the west.

To the east of the East Humboldt Mountains there are three lakes, known in their order from south to north as Ruby, Frank- lin, and Eagle lakes. These hold the same relation to th(» lofty peaks adjacent to them on the west as Pyramid and other lakes to be described occupy with respect to the Sierra Nevada. The lives of the lakes supplied by the drainage of the East Hum- boldt Range are less secure, however, than in the case of the larger lakes fed by streams from the gi*eater range to the west. In winter they are flooded, the water supply being in part fur- nished by fissure springs; and in summer they decrease in area, and occasionally their basins l)ecomc dry.

Ruby Lake, when in its normal winter contlition, is about 16 miles long, and has a nearly uiiirorm width of perhaps '2 miles. It is separated from Franklin Lake, to the north, by a narrow gravel bar formed by waves and currents in an extinct water body much larger than both of the present lakes combined. Franklin Lake is 15 miles long, with an average width from east to west of 4 miles. Eagle Lake, '-2 miles imrtliward from the one jiist mentioned, is more irregular than its companions, and is about 7 miles in diameter.

110 TEESEXT AND EXTINCT LAKES OF NEVADA.

The watei's of these lakes are shghtly alkaliue, but in wiuter and spriug are not unpleasant to the taste. They are playa lakes with a longer period than most of tlieir companions of the same t^1^e, and might with propriety be termed scmiperciDiidl. To this iirovisional subclass might also be refeiTed the lakes of the Carson Desert, since, previous to the time their tributary streams liegan to be diverted for irrigation, they were e\ap- orated to dryness only in occasional years of gi'eat aridity.

Hundreds of other inclosed basins, jiarticidarly in southern Nevada, are partially flooded in winter in a similar manner to those already enumerated, and become desert plains of hardened mud in sunmier. Various jiortions of the region surrounding Nevada, and especially those embraced ■within the boundaries of Utah, Arizona, and California, experience changes similar to those just described, and illustrate some of the most striking peculiarities of a region where the topogi-aphic and climatic conditions favor the existence of temporary lakes.

Perexxlu. Lakes. — Lakes which exist for a term of years, and hence termed ju'rennial, may be convenientlj' divided into two classes: namely, those that overflow, or normal lakes: and those that do not rise sufficiently to find an outlet, or inclosed lakes. By normal lakes is meant the class of lakes characteristic of humid regions, and hence the most abundant and most famil- iar the world over. They are commonly expansions of rivers, and overflow.

These two subclasses, as in the case of ephemeral and peren- nial lakes, are not limited 1 >y definite Ijoundaries. Inclosed lakes are sensitive to climatic changes, and may increase in vohime until their surfaces are raised to the level of the lowest point in the rims of their basins, and be transferred temjxirarily or i:)er- manently, if the climatic conditions remain favorable, to the list of those which usually give origin to streams. Numerous exam- ples in Nevada and adjacent regions might be cited of lakes which have been known to undergo changes that have transferred them many times from one sul)class to another.

Some of the ephemeral lakes of Nevada which are not suflS- ciently permanent to have a name, or to be recognized as lakes l)y the settlers of the region where they occur, o\erflow during their brief existence, and, if this one feature is alone used in classification, would belong to the class of water bodies charac-. teristic of humid regions. It will be seen, therefore, that the

NORMAL PEKENNIAl, LAKES. Ill

classification i)iopu.sed aljuve is simply for (•onvenicucc, and does not imply stable conditions.

NoKMAL Lakes. — The list of normal lakes in Nevada is short. There ai-e two only — Lake Tahoe and Lake Humboldt — that can consistently Ije placed in the same category as the tens of thou- sands of lakes found in humid regions.

Lake T((hoe. — This " ({em of the Sierras," as it has been a])tly called, is situated partly in Nevada and partly in California. The depression it occupies, like the majority of the basins de- scribed in this paper, was foi-med by unequal movement of lai'ge masses of the earth's crust ((UasfropliisDi). The outline of tlie valley in the mountains which the lake has ajipropriated has been modified to some extent by streams and glaciers, but not suffi- ciently t(^ destroy the characteristic features resulting fi-om the great disturljances that gave it birth.

Lake Tahoe is surrounded by some of the finest scenery of the Sierra Nevada, and is especially pleasing on account of the breadth of view obtained from many jtoints on its sliores. The mountains surrounding it are clothed with coniferous forests to within a few hundred feet of .their angular summits. Their more rugged lines are thus subdued, and given a picturesqueness that is entirely lacking on the shores of the desei't lakes.

This lake is 21 miles in diameter from north to south, and 1 2 from east to west. It is 195 square miles in area, and receives the drainage of 922 square miles of territory. Its elevation above the sea is t),202 feet. Soundings made l)y Professor John Le Conte gave a depth in the central part of 1,(545 feet. This measure maybe exceeded when a morc^ systematic survey of the contour of the bottom is made. Next to Crater Lake, ( )regon, it is the deepest lake yet measured in North America. Its waters, of gi'eat pm'ity and of wonderful transparency, are inhabited 1)y splendid trout and other fishes in abundance. The overflow escapes through a rocky gorge, and foi'ins Truckee River, — a clear, swift stream, which, after a tortuous course of about 100 miles, empties itself into Pyramid aud Winn(Mnucea lakes.

Lake Tahoe, situated among mountains that rise tVom seven to ten thousand feet above the sea, the swift bright rivei- flowing from it, and the alkaline and saline lakes formed by the retention of its surplus waters in desert valleys, furnish a geogi-aphical unit in which many of the marked contrasts between humid and arid lands are Avell illustrated. A careful study of this

112 PUESEXT AXD EXTINCT LAKES OF NEVADA.

single, eireumscnbed drainage area would furnish one of the most complete and instructive lessons in physical geography that our country affords.

Jlouiitain Tania. — To make an account of the existing lakes of Nevada complete, it is necessary to mention a few small tarns situated in deep recesses on some of the higher mountains. In the portion of the Sierra Nevada included within the boundaries of the State, on the East Humboldt Eange, and about Jeff Davis Peak, there are small basins at elevations of from eight to ten thousand fi»et above the sea, which are filled usually to over- flowing with clear, sweet water. These depressions are either in solid rock, or are formed in part by terminal moraines left by ancient glaciers. They are of a type common in mountains that have been ice-covered, but are exceptional, and are not a characteristic feature of the arid region in which we ai"e now especially interested.

Hitmholdt Lah'. — Huml>oldt River, after flowing for some three hundred miles through treeless valleys, and just before reaching the Carson Desert, meets an obstruction that holds its waters in check, and causes an expansion known as Humboldt Lake. The dam which blocks the way is an immense gravel bar which extends completely across the valley, and was formed in an extinct lake (Lake Lahontan, to be described later). This bar, as may lie seen from the map forming Plate IV., has many of the features of a railroad embankment. It is formed mostly of gravel and sand swept from the margins of the old hxke and deposited in deeper water when the loaded currents were deflected from the shore. Its length from the cliffs on either side of the valley is about 4 miles. Its top is from 50 to 125 feet above the adjacent phun. The river was held in check by this obstruction when the old lake was lowered below its crest and formed a secondary lake. At some time in its history the lake overflowed, and cut a narrow channel through the obstruction that held it, and was partially drained. In recent years an artificial dam has been placed in the opening, which, when in repair, causes the lake above to ex- pand. During summer seasons Humboldt Lake seldom over- flows, and is then the lower limit of the drainage system of the river from which it takers its name ; but in winter and spring the waters escape southwai-d, and spread out on the desert so as to form a shallow water sheet, known as Mirage Lake. Farther southward, on the northern part of Carson Desert, the water

INCLOSED PERENNI.U. LAKES. 113

again expands, and foi'nis the principal source of North Cai'son Lake, ah-eady described.

In the summer of 1882, when examined by the ■writer, Hi;m- l)oldt Lake covered an area of about 20 square miles, and did not overflow. Its waters were somewhat alkaline, owing to evaporation from its sm-faee and from the river feetling it. Its depth was aljout 12 feet over the greater part of its area.

The aljiiormal character of the lakes of Nevada, as would appear to a visitor from lands enjojdng a more humid climate, is shown by the fact, that, with the exception of moimtain tarns, there are only two lakes Ijelonging to the class normal to regions of abundant rainfall. Of these, one is but partly in Nevada and at a high elevation among mountains, and the other over- flows only during the rainy season, and, if its natural discharge had not been obstructed, might possibl}' be included among ephemeral lakes.

Inclosed Lakes. — The lakes of Nevada which, next to the playa lakes, best iUustrate the climatic conditions thei-e prevail- ing, are the perennial lakes that do not overflow. Here again the list is short. The only examples that can be found are Pyr- amid, Winnemueca, and Walker lakes. The characteristics of these lakes are of interest not only in the study of the present geography, but because they form a supplementary chapter to the history of Lake Lahontan, which occupied the same I'egion at a comparatively recent date.

Pi/ramid and Winnemueca Lakes. — The Truekee Rivei-, as already stated, discharges into both Pyramid and Wiinienuicca lakes. On reaching the valley in Avhich these lakes are situated, the river divides in much the same manner as many streams send off distriljutaries on flowing over their delta. The propor- tion of water reaching either lake is variable, and depends on the nature of the obstruction formed in the channels of the river below whei-e it divides. At times the entire supply goes to a single lake, and occasionally one lake Ijecomes trilnitary to the other. The lakes are siibjected to fluctuations from this cause, as well as from variations in climatic conditions.

The accompanying map of Pyramid and Winnemueca lakes (Plate II. ), made in 1882, will obviate the necessitj'- of a descrip- tion of their more pronounced features.

Pyi-amid Lake was first made known to civilized man by Gen- eral Fremont, who traversed its eastern shore in 1844, and named

lU

PRESENT XSD EXTINCT LAKES OF NEVADA.

it ill reference to the peculiar form of an island near its southern end. This island, as may be seen from the accompanying: ilhis- tration, has a remarkable resemblance to one of the I'yramids of Egyi't.

Pyi-aiiiiil Islaiul, P_%Taiiii(l Lake, Nevada.

The lake has a length of :)() miles, and near its northei-n end is 12 miles broad. Its area in September, 1882, was 828 square miles. Wiiiiiemucea Lake at the same date was 29 miles long, with an average ])readth of 3i miles, and an api)roximate area of 91 square miles.

The sub-lacnsti-al contours given on the map (Plate II.) indi- cate, that, if the waters 'of these lakes were withdrawn, the basins they occupy would have api)roximately the same charac- teristics as may be observed in many adjacent valleys in which playas occupy the lowest depressions. This fact, together with

INCLOSED PERENNIAL LAKES. 115

others that will be mentioued later, suggests that even these broad lakes were formerly reduced to the condition at present illustrated l)y niauy eiihemeral lakes.

The waters of both Pyramid and Wiunemucca lakes are saline and alkaline. The chemical composition of the matter in solution is shown in the table on p. 117. Like all inclosed lakes, they are sensitive to climatic changes, and exhibit Ijoth seasonal and secular variations. They record the net balance between rain- fall and evaporation, and rise and fall with changes of humidity nuich as a liarometer fluctuates with variations in atmosplici-ic pressure. This fa<'t is the more apparent, since the lakes receive scarcely any water supply from other sources than the Truckee River. The springs tributary to them are few in number and small in volume. The rain falling on the adjacent land can be safely assumed as not exceeding five inches annually, and is so distributed that it is mostly absorbed by the pai'ched soil, or evaporated, liefore it can gather in rills and find its way to the lakes.

Much might be said of the rugged [>icturesqueness of the mountains aljout these dead seas, of the peculiar islands bivak- ing their surfaces, of their abundant fish life, of the varying tints of their waters, and of the manner in which carbonate of lime is being eliminated from them through the agency of low forms of plant life; l)ut space will not jtermit.

]\^(ilkei- Lake. — This lake, likt^ the two just described, is fed almost entirely l)y the snow and I'ain falling on the Sierra Nevada. The immediate source of supply is Walker River. Surveys made in 1SS2, from which the map forming Plate 111. was constructed, showed that Walker Lak(^ was then 25| miles long from north to south, and had an average breadth of between 4^ and 5 miles. Its area- Avas about 9.j sijuare miles. The greatest depth oljtained by such soundings as it was iH'ac- ticable to make was 225 feet. The waters are alkaline and unfit for human use, although drunk by animals. The chemical com- position is given on p. 117.

The west shore of Walker Lake is bordered l)y a precipitous mountain range, which rises from the water's edge so abruptly that not room enough for even a bridle path intervenes. This mountain ridge is the uptiu'ned bordei- of a tilted block of the earth's crust, and is bounded on tlie (Hist by a ]irofound fracture. The Ijlock on the east side of the fracture has sul)sided with

ll(j PRESENT AND EXTINCT L.UCES OF NEVADA.

reference to the west side, and the depression thus formed is oc- cupied by the present lake. Like many of the valleys of Nevada, this is a typical fault liasin. The exceptional depth of tlie lake is probably due to recent movements of the fault that gave it origin.

Crater Lakes. — On the western side of Carson Desert there are two circular depressions Avith elevated rims that are filled with intensely alkaline water. These are known as Soda Lakes, and, from their proximity to a former settlement called Rag- town, are sometimes designated as the "Ragtown Ponds." The larger lake has an area of 298i acres; and the smaller is a pond of varia1)le size, much modified in recent years by excavations. The rim of the larger lake in its highest part rises 80 feet above the surrounding desert, and is 165 feet above the lake it incloses. The outer slope of the rim is gentle, and merges imperceptibly into the surface of the surrounding desert; but its inner slope is abrupt and in places precipitous. A series of careful sound- ings made in the lake show its maxinnim depth to be 147 feet. The total dei)th of the depression is therefore '212 feet.

This great hole in a nearly level plain, as shown by the struc- ture of its walls and the nature of the material composing them, is of volcanic origin. It is a volcanic crater from which dust, lapilli, and bombs a foot or two in diameter, have been Aiolently ejected, but which did not pour out liquid lava. The diameter of the crater from opjiosite jioiuts in its rim varies from a mile and a half to two miles. This volcano is situated in the basin formerly flooded by Lake Lahontan, and was in activity before that lake disapi)eai-ed, as well as at a later date. The waters now occupy- ing the crater find their way to it by percolating throiigh the thick lake beds that floor the Carson Desert, and owe their high per- centage of saline matter to the salts dissolved from the rocks through which they find their way.

The 8oda Lakes are the basis of a considerable industry in carbonate and bicarbonate of soda. The various salts they con- tain are indicated in the table on p. 117. These lakes are excep- tional in character, and have but slight bearing on the study of climatic change from which most of the lakes of Nevada derive their chief interest.

Analyses of Lake Watei!s. — In order to com])lete an out- line of the data now availaljle concerning the existing lakes of Nevada, the following table, showing the chemical composition of the matter in solution in then- waters, is here inserted. Analy-

SUMMARY OF PRESENT LAKES.

ii;

ses of two saline aud alkaline lakes in the regions adjacent to Nevada are also presented for comparison.

Analyses of the Wtiters of Lakes in the Arid lieijion^ (Parts in 1,000).

ComtituentSL	Abert Lake. Oregon.^	Great Salt Lake, ntab. (1860.) 49.090 2.407 .2.55 3.780 83.946 9.858 Trace.	Huraboldt Lake, Nevada. .27842 .00083 .01257 .01648 .29545 .20120 .03040 .00069 Trace. .03250	hnda Lake, Nevada.	Pyramfd Lake. Nevada.	Walker Lake. Nevada.	Wlnne- i Lake murca Takue, Lake. California- Nevada. Nevada.
boiliuiii (Na) Potassium (K) .... Calcium (Ca) Magnesium (Mg) .... Chlorine (CI) Carbonic acid (CO;)) . . Sulphuric acid (^04) . . Pliosiihoric acid (Ill'll4) . Boracic acid (13407) . . Silica (SiO.2) Hydrogen (in bicarbonates)	14.245 .621 13.055 9.199 .685 .224 .050	40.919 2.357 .^45 40.851 10.858 11.857 .286 .278	1.1796 .0733 .0089 .0797 1.4300 .4990 .1822 .0334	.85535 Trace. .02215 .038.30 .58375 .47446 .52000 .00760	1.2970 .0686 .0196 .0173 1.6934 .3458 .1333 .0275	.0073 .0033 .0093 .0030 .0023 .0287 .0054 .0137
	37.985	149.930	.92860	113.651	3.4861	2.50160	3.6025	.0730

1 Compiled principally from Table C, in U. S. Geological Survey Monograph, vol. xi.

2 Analyses by T. M. Cliatard, x\merican Journal of Science, ser. 3, vol. xxxvij., 1888, pp. 146-160.

The analysis of the water of Lake Tahoe shows that it is of gi'eater purity tlian the average of fresh-water lakes and streams.

SuMMAiiY RESPECTING THE ExisTiN(; Lakes. — As may be seeu from a glance at a map of Nevada, all the larger lakes that diversify her surface are near the western border, and are sup- plied by precipitation on the Sierra Nevada. Hundreds of basins, some of them scores and even Imndreds of stpiare miles in area, and so inclosed as to be suitable for holding broad lakes, exist throughout the State, liut the aridity of the region pre- cludes their being occupied by perennial water liodies. In many instances the annual rainfall in these desert basins is so meager that it is at once absorbed by the thirsty soil, or returned to the atmosphere as vapor, and not even ephemeral lakes are formed. This is especially true of the southern portion of the State, where no lakes occur except a few pools fed principally by fis- sure springs.

Should the Grreat Basin, as the ai-ea of intei'ior drainage between the Sierra Nevada and Wasatch Mountains is termed, experience a change of climate of such a nature that the rain- fall would be increased or evaporation dimiiiislied, the most obvious result would lie the appearance of lakes in valleys that are now either dry tliroughont the year (»■ hold playa lakes, and the expansion of the perennial lakes. The lakes

118 PRESENT AND EXTINCT LAKES OF NEVADA.

uow supplied liy streams from the Sierra Nevada, and the niueh smaller lakes at the base of the East Humboldt Mouii- taius, would expaud, and invade the adjacent valleys until they exposed sufficient surface to the atmosphere to counterbalance the inflow by evaporation. If before this stage was reached a lake rose sufficiently to find an outlet, it would overflow, and become tributary to some lower basin. The manner in which the present perennial lakes fluctuate, and the appeai'anee and vanishiniT of playa lakes from season to season or in response to climatic oscillations ha\"ing a longer term, suggest that only moderate climatic changes of the nature above indicated would be requii'ed to prodiice marked results in the appearance of the basins of Nevada.

The study of the surface geology of the Great Basin has shown that a climatic change of the natm-e just suggested did occur at a time not remote. The streams from the mountains increased in volume ; many channels were occupied by flowing water that are now dry throughout the year ; lakes ai)peared in many and probably in all of the inclosed basins that are now arid ; the perennial water liodies expanded until they became veritable inland seas. The records of the time when Nevada was a lake I'egion are fresh and easily read. Let us see what thoughts their study will suggest.

EXTINCT LAKES.

Intimately associated with the lakes in the valleys of Nevada, referred to above, are the records of glaciers on the Sieri'a Nevada, East Humboldt, and other mountains. For this and other reasons the extinct lakes here considered are referred to the Pleistocene division of the earth's history, or the time immediately preceding and merging into the time of man.

Pleistihexe Lakes. — Many valleys, of Nevada might be enu- merated which were occupied by lakes i>revious to-the present time of aridity. There is probaljly not an inclosed basin in the State but what had its lake during Pleistocene times. What is now in great part a desert land was then a lake region with as gi'eat a water surface, in reference to its area, as the pi-esent lake region of central New York or of northern England. Unlike many lake regions at the present day, however, a large number of these ancient water bodies did not overflow, and at times at

EXTINCT LAKES. Hi)

least were saline aud alkaline. The configuration of the land was such as to lead to the existence of two gi'eat inland seas that outranked their neighbors, the histories of which are of unusual interest.

One of these seas, named Lake Bonneville, occupied Salt Lake valley, Utah, and several depressions opening from it, and was supplied mainly Ijy streams flowing westward from the Wasatch Mountains. A contemporary lake, called Lake Lahou- tan, situated in northwestern Nevada, and extending into Cali- fornia, was supplied principally l)y streams flowing eastward from the Sierra Nevada. Lake Bonneville was the larger and deeper, and overflowed. Lake Lahontan, on the other hand, never overflowed. Owing to the absence of an outlet, it imder- went many fluctuations in vohmie aud composition, and left the most interesting and instructive chemical records of any lake known. Lake Lahontan was 886 feet deep in the deepest part, had an area of 8,422 square miles, and received the rainfall of 40,000 scpiare miles.

The regions draining to these two great la-kes occupied the entire space between the Wasatch Mountains and the Sierra Nevada, and for a distance of 2.') miles near the northern pai-t of the Utah-Nevada boundary their hydrographic l)asins had a divide in common. The smaller Pleistocene lakes at the base of the East Humboldt Mountains, previously mentioned, were situ- ated to the south of these two drainage areas.

Lake Lahontan. — Should a climatic change occur of such a mxture that it would allow Pyramid, Winnemucca, and Walker lakes to expand until they became confluent and invaded manj'' adjacent valleys, and continued to increase in depth until the sounding line in the deepest part showed 886 feet of water, the appearance of Lake Lahontan at its highest stage would bo prac- ti(_"a.lly restored.

Tlie outline of th(^ lake is indicated on Plate I., from which the valleys it occupied, and the extreme irregularity of its out- line, may be ascertained at a glance. One of the peculiar geo- graphic features is that the lake surrounded a large, irregular island, on which there was a smaller lake. So far as knoAvu, this island lake did not OA-(M-flow. A broad playa now mai'ks its site.

The records left by Lake Lahontan during its various flu(,'tua- tions may be groiiped in two main classes, physical and chemical.

1'20 PRESENT AND EXTINCT LAKES OF NEVADA.

The Physical Eecoeds. — The vim of the Lahoutau bashi has beeu traced throughout its entire extent, and found to be unbroken by a channel of overflow. The water body it held was therefore an inclosed lake, and, like others of its class, must have been subject to repeated fluctuations of level. That such was its history, is also e%-ident from the multitude of teiraces still remaining as records of its changes. In this as in all abandoned lake basins, the elements of shore toi)Ograi>hy to which we turn for a large pai't of the history of the vanished waters are terraces, sea cliffs, emliankments, and deltas.

Terraces and Sea C/(//k — The most common of the records inscribed on the borders of the Lahontan basin are wave-cut ten-aces. These may be traced through a large portion of the basin, but are most distinct on the liorders of the larger deserts.

In traveling over the Central Pacific Railroad between Gol- conda and Wadsworth, one is seldom out of sight of the long horizontal lines drawn by the waves of the ancient lake on the shores that confined them. Eecords of the same character may be traced continuously about the borders of the Black Rock and Smoke Creek deserts, and are strongly defined along the bases of the mountains overlooking Pyramid and Winnemucca lakes. They are again plainly legil >le on the steep slopes Vior- dering Walker Lake, as may be obsex-ved by the traveler over the Carson and Colorado Railroad.

The highest of these numerous shore lines has been named the Lahontan Beach, as it records the highest water stage of the former lake. Its elevation above the sea is 4,343 fee at Mill City, and from 4,418 to 4,4*27 feet at the loAver end of Humboldt Lake. These measurements, together with many others, show that the old beach is not now honzontfd. Movements have taken place principally along numerous fault lines, and the relief is not now precisely the same as when the old lake existed. An average of the various measurements indicates that the pres- ent elevation of the Lahontan Beach is about 4,378 feet above the sea. This is the nearest ajiproximation we can make to its original altitude.

Besides the Lahontan Beach, there are three other water lines of sufficient importance in the history of the lake to de- serve special designation. One of these is a strongly defined terrace 30 feet below the Lahontan Beach, and at the upper limit of a calcareous deposit precipitated from the waters of the

TEKEACES OF LAKE LAHONTAN.

121

ancient lake, and described later, whit-li has been named litlwid tufa. This, thei-efove, is called the Lithokl Terrace. Its eleva- tion is 50(J feet above the 1882 level of Pyramid Lake, which was then 3,783 feet above sea level.

Another chemical deposit, known as dendritic tufa, occurs in great quantities in the same basin. At its upper limit it is bounded by a water line, usually but poorly defined, named the Bt'iidrific Terrace. Its elevation is 320 feet above the datum plain just mentioned.

Between the Dendritic Terrace and the surface of Pyramid Lake there is a broad platform, which is the strongest and best

Fwrt

Laliniitin Beach . . 530 l.iihiiiilTerrai-f... 50O

UcMilritic Ti-rnii-i'. S->0

^t^<.ii.i»ttfys^^ ■ Thinolite Terraco. 110

^^,_,^. — __ rSurfai'e of Pvni-

^^^ mill LakL-(lss-.>). 0

Generalized Profile of Lahontaii Shores.

defined of all the Lahontan water lines. It marks the upper limit of a third variety of tufa, known as thii/olife, and is there- fore called the ThhioJitc Terrace. Its elevation is about 110 feet above the level of Pyramid Lake in 1882. This terrace has T)eeu found to extend entirely ai'ound the valleys occui)ied by Pyra- mid and Winnemucea lakes, and may also be followed, though less distinctly, about the borders of Black Rock, Smoke Creek, and Carson deserts.

The terraces just named, together with the 1882 level of Pyramid Lake, furnish four definite horizons that will be found cohvenient reference plains in tracing the Pleistocene history of the basin. It is only at exceptional localities, however, that these terraces can be followed for any cousideraVjle distance, and at only a few points could a sequence like the one shown above be obtained. The relative age of the various water lines indi- cated in the diagram will be discussed when the chemical history of the lake is considered.

12'2 PRESENT AND EXTINCT LAKES OF NEVADA.

The highest terrace of all, the Lahoutau, is au iueouspicuous feature iu itself, but it is important as forming the boundary between subaorial and subaqueous sculpture on the sides of the valleys. It usually appears as a terrace of construction a few feet wide, resting on the broad Lithoid Terrace 30 feet below.

Besides the more definite and strongly marked terraces to which names have been given, there are a large number of less deeply engraved lines on nearly every portion of the fonuer shore. Each of these scorings is the reeoi-d of a pause in the fluctuations of the water surface. Collectively they indicate numerous changes in the lake level. The obscurity and want of strength in many of them are no doubt due in a great meas- ure to the fact that the slopes on which they were traced have been brought within the reach of wave action many times. In this way the i-ecords first made have been erased or obscured by subsequent additions.

Bars (1)1(1 Enihdi/Jciiienfs. — At many localities in the Lahontan basin there are extensive embankments of gravel and sand de- rived from the cutting of some of the terraces just referred to.

An instructive example of the constructive action of the waves and evirrents is shown on the map forming Plate IV., of the gi'eat gi'avel embankment now retaining Humboldt Lake. The map referred to is from plane-table sm'veys made by Mr, Willard D. Johnson of the I". S. Geological Sm-vey, and is so graphic that it requires but little interpretation.

As previously stated, Humboldt Lake owes its existence to the damming of the river tributary to it by extensive gi-avel embankments which were thrown completely across its channel during the time that Lake Lahontan occupied the valley. The highest level of the ancient water smface is represented on the map by a heavy l)roken line, and appears in the topography of the countrj' as a gravel embankment, or as a wave-cut terrace at the base of a sea clitf sometimes a hundred feet in height.

The valley in which Humboldt Lake is situated was a strait at the time of the higher stages of Lake Lahontan, and con- nected the Carson body of the former lake with the waters that occupied the northern part of the Humboldt valley. At a late stage in the ancient lake an embankment of gravel from 50 to 12") feet in height was carried completely across the valley iu such a manner as to suggest that it is au artificial structure intended to confine the drainage. At either end the main em-

BAKS AND SEDIMENTS OF LAKE LAHONTAN. 123

baukment ■widens as it approaches the shore, aud forms hoa\y triaiigiahxr masses of gi'avel, on the surface of which appear many smaller bars built of clean, well-worn shingle. These secondary bars form ridges with rounded crests, fi-om a few feet to 30 or 40 feet in height, and ueai-ly level-topped foi- long distances. These are seldom straight, l)ut curve with beautiful symmetry, each gracefully bending ridge marking the course of a current in the waters of the ancient lake in which it was formed.

The embankment crossing the valley declines gently in height from either end toward the center, and has been cut through at its lowest point by the overflow of Humljoldt Lake. The gap carved by the outflowing waters is shown in the profile at the bottom of Plate IV. The diagi-am was constructed from a line of levels run from the Lahontan Beach on the Niter Buttes to the highest water line on the west side of the vallej'.

At many other localities about the abandoned shores there are fine examples of gi'avel bars and embankments which show many details, and serve as records of fluctuations and of changes in the direction of the shore currents in the old lake.

Sediments. — The tril)utaries of lakes, disregarding organic substances, contain two classes of iminirities : (a) minei-al mat- ter in suspension, and {/>) mineral matter in solution.

Besides holding fine silt in suspension, streams also roll peb- bles aud stones along their beds. On entering a lake, all tliis material subsides more or less quickly, forming lake beds, gravel deposits, etc. In the sedimentation of lakes, the coarser and heavier debris is invariably di-opjied near shore, while the finer and lighter suljstances are floated to a greater distance befoi-e suljsiding. In this mannei" coarse shore and fine ofl'sliore de- posits originate.

The sedimentary deposits of Lake Lahontan exhiVdt three definite divisions : viz., upper lacustral clays, from 50 to 75 feet thick ; medial gi'avels, from 50 to 200 feet thick ; lower lacustral clays, not fully exposed, but at least 100 feet thick. A^^lerever any considerable section of Lahontan sediment is seen, these three divisions appear in unvarying sequence.

The upper and lower members of the series are composed of marly days, which show by their fineness, and the evenness of their lamination, that they were depo.sited in deep still water. The middle member, on the other hand, usually consists of well- rounded gravel and sand, in some instances becoming coarse,

«

1:24 TRESEXT AND EXTINCT LAKES OF NEVADA.

aud including bowlders a foot or more iu diameter. This deposit is current-bedded, aud exhibits many variations, indicating that it was deposited in shallow water.

The interpretation of this section gives an outline of the later Pleistocene history of the Lahoutan basin. There were two high- Avater periods during which tine clays were deposited. Separat- ing tliese, there was a time when the lake was low, and allowed current-borne gi-avels to be carried far out over the previously formed lake beds. During the second flooding especially, the waters underwent long concentration, and at certain stages deposited vast ipuuitities of tufa; during this stage, also, the lake received large quantities of pumiceous dust, thrown out by volcanoes in violent eruption. The secoml rise of the lake was followed by the present period of desiccation, which wit- nessed the evajioration of its waters, and the exposure of its sediments to subaerial erosion. The rivers, in flowing across the exposed lake beds, carved the deep channels we have de- scribed, and are now spreading stream- and current-borne gi'avels far out in the central portions of the valleys, thus in nniny ways repeating the conditions that characterized the time during which the medial gravels were deposited.

The Chemical Records. — Lake Lahoutan belonged to the class of inclosed lakes of which the Dead Sea, Caspian Sea, and Great Salt, Mono, Pyramid, Walker, Winnennicca lakes, etc., are existing examples. Lakes of this class are supplied mainly by streams in the same manner as the far more numerous class of lakes with outlets, l)ut the inflow is counterbalanced solely by evaporation.

The waters of streams and springs are never chemically pure, but contain mineral matter, such as carbonate of lime, common salt, etc., in solution. As evaporation takes i>lace from the sur- face of an inclosed lake to which such waters are contributed, the relative amount of saline matter it holds is inci'eased until the point of saturation for one or more of the contained salts is reached and precipitation begins. Changes of temperature aud the vital action of plants aud animals may retard or hasten the time when some of the salts liegin to be eliminated ; but, in general, con- centration continues, if the life of the lake is sufficiently pro- longed, until the once sweet and wholesome waters become dense brines. In the Dead Sea, for example, the total solids in solution amount to about 24 per cent ; tliat is, about one fourth

CHEMICAL DEPOSITS. 1'2.")

the weight of a given vohime of the l)rine is due to material held iu sokitioii. Oceau water contains about 3.5 per cent of saline matter. These may be called "standard l)rines,'' with which interesting comparisons may be made of the analyses of the water of the present lakes of Nevada already given.

The principal streams tril)utaiy to Lake Lahontaii occupied the same channels through which Carson, Walker, and Truckee rivers now flow. It is safe to assume tliat the chemical com- position of the waters <lischarged tlirough these channels at the present time is a fair api>roximatiou to the comiiosition of the streams that emptied into the old lake, exce^jtiug that, when the precipitation was more abundant than at present, the percent- age of saline matter iu solution was somewhat less than is now carried. Analyses have shown that the waters at present tribu- tary to the Lahontan basin have about the nonnal composition of surface streams, which, as found from analyses of a large number of typical rivers in lioth America and Eurojic, carry 0.01888 per cent of total solids in solution, of which one half, or 0.00887 per cent, is calcium carbonate (carbonate of liTue).

As Lake Lahontan never rose so as to overflow, all of the saline matter carried into it uuist still remain iu its l)asin.

Calcarmns Tufa. — The traveler who crosses the dee2>er valleys formerly occupied by the waters of Lake Lahontan cannot fail to have his attention attracted by curious and frP(iuently fan- tastic rock masses, the like of which is seldom seeu elsewhere. These strange forms rise from the gi'ay desert like huge mush- rooms, or iu clustered tower-like structures having a striking resemblance to half-ruined castles. They vary in height from a few feet to fully a hundred feet, and not infrequently are several hundred feet in circumference. Some of the most remarkable of these forms occur about the shores of Pyramid and Winne- mucca lakes, or rise from their bottoms, and form uni<pi(> islands. The general appearance of one of these structures is sliowu on p. 126. The reader will see at once that these nearly jierpeii- dieular towers with rounded dome-shaped sumuiits are not the result of erosion, but still present their original outlines.

These remai-kable mushroom-shaped and castle-like forms are composed of calcium carl)Oiuxte. Tliey owe tlieir origin to the precipitation of the stony matter comp(»siHg tliem from the waters of Lake Lahontan. In geological language, this rock is calcareous tufa.

12(i

I'KESENT AND EXTINCT LAKES OF NEVADA.

On the borders of tlie deserts that were formerly flooded, and on the hills and buttes rising with them and once existing as islands, there are vast deposits of tnfa which sheathe the ancient shores to within thirty feet of the highest beach line. Tlie thick- ness of this deposit is in some instances upwards of eighty feet.

Tula iiciHisils on liic Sliorc of Pyramid Lake.

The total amount of these rocks of cheinieal origin is astonish- ingly great, and can only l)e estimated in millions of. tons. In no other known instance is there such a magnificent display of rocks formed l)y precipitations from lake waters.

If one halts in his journey across the bed of the ancient sea of Nevada, and examines the structure of the tower- and castle- like forms that attract his attention, very interesting facts may be observed.

CAIiCAKEOUS DEPOSITS. V2l

111 some instauces tliQ towers have fallen, and sections of their interiors are revealed. It will then be found that they were l)uilt up hy the successive deposition of layer on layer of stone. When the sections are approximately circular, these layers appear as concentric bands, not unlike the annual rings in the trunk of an oak, but frequently they are several inches and even two or three feet liroad. It will also be noticed that three varieties of tufa are present, and that each variety shows many minor subdivisions marked by changes in structure, color, etc. As one proceeds with this examination, the evidence becomes conclusive that even the largest of the water-built cas- tles began by the precipitation of carbonate of lime about a solid nucleus, and grew slowly by the addition of successive layers of the same material. The manner iu which these deposits wei-c formed, and the astonishing results attained, show tliat a gi-cat lapse of time was required for the process. The life of the old lake must have embraced at least several thousand years.

The inner core of the tufa towers, and the tirst layer formed on the sides of the basin, consist of a compact, stony variety of tufa, having in common with the subsequent deposits a yellowish color. On account of its compact texture, this lias l)een called Uthoid iiifd. Its thickuess in many instances is from ten to twelve feet; but, as it is usually concealed by both chemical and mechanical deposits of later date, its maximum thickness is probably not known.

Inclosing the Uthoid tufa in the towers and castles, and form- ing a superimposed layer on the first incrustation sheathing tln> cliffs, is a second variety of tufa composed of rough but well- defined crystals, that are frequently six or eight inches long, and an inch or more in diameter. These crystals are known as tli'm- olifr, and the name fJiiiioHfic tufa has been given to the deposit of which they formed the major part. The thickness of this variety is from six to eight feet at its upper limit, and from ten to twelve feet at the lowest horizon exposed.

Succeeding the thiiiolitic tufa, and forming the most abun- dant deposit of calcium carbonate in the basin, is a third pre- cipitate of the same general nature as those just mentioned, but having an open, branching structure, ami strongly resemltling a mass of symmetrically arraiigeil twigs changed to stone, and for this reason named dendritic tufa. In many instances this deposit is fully sixty feet in thickness.

128 PBESEXT .VXD EXTINCT LAKES OF NEVADA.

The vertical rauge of these three varieties of tufa varies in au interesting manner. Their limit above the 1882 level of Pyr- amid Lake is shown in the figure on p. 121, where the horizou of the terrace with which each is associated is intlicated.

The lithoid tufa extends up the rocky borders of the valley 500, the thinolitic 110, and the dendritic 320, feet above Pyramid Lake. How much below the level of the lake they may reach is not known, but the domes and islands of the same material rising from its waters have their bases deeply submerged.

The lithoid and thinolitic varieties are thickest at the lowest horizons exposed. The dendritic tufa reaches its greatest de- velopment near its upj^er limit, and frequently hangs from steep cliffs like a massive thatch. In some instances it is so abun- dant at elevations of from 200 to 300 feet above Pyramid Lake, that it gives a decidedly convex outline to the slopes to which it is attached.

At certain localities on the Carson Desert and about Pp'amid Lake the surface of the lake beds partially tilling those basins is covered over large areas with polygonal blocks having rounded summits. Each block in these closely set pavements is a mnsh- room-shaped growth of tufa from ten to twentj' inches or more in diameter. These blocks were at first circular in outline, but pressed against one another as they enlarged, and thus received an angular outline, as seen from above.

The base of each separate accumulation of tufa, whether- a mushroom-shaped growth a few inches in diameter or a great castle-like form a hundred feet in height and two hundred feet or more in diameter, is a pebble or nucleus of rock about which crystallization began. Wherever there was a solid crag in the old lake suitable for the attachment of the lime precipitated from the water, it became incrusted, and, as the process contin- ued, grew into an imitative form. Detached rocks and islands were especially favoraljle as centers of aecunmlation, and be- came hea%-ily loaded. The borders of the valleys, where com- posed of solid rock, were also covered, and frequently concealed Vieneath p6ndant masses of tufa resembling gigantic honey- combs.

Tlic Mure Solnhle Salts. — As shoAvn by the average composi- tion of river water, about one half of the total solids earned in solution by surface streams is calcium carbonate. This is the most diflScult of solution of anv of the salts ordinarilv found in

OTHER CHEMICAL DEPOSITS. 129

such waters, and the first to be precipitated when conceutratioii by evaporation takes place. The more soluble salts consist mainly of sodium sulpliate, sodium carbonate or bicarbonate, sodium chloride, silica, magnesium, potash, iron, etc.

The amount of these more soluble substances carried into Lake Lahoutan must therefore have been about equal to the amount of calcareous tufa precipitated. As the lake never over- flowed, these salts must still exist in its now nearly desiccated basin; yet, in riding through the valleys that wei-e formerly flooded, no deposits of the salts referred to can he foun<l, at all commensurate with the vast quantity of calcium carbonate that attracts one's attention. The disappearance of the salts referred to seems to be satisfactorily explained in the following hypothesis : —

After the last gi'eat rise of Lake Lahontan, there was a long- continued episode during which its basin was more arid than at present. Evaporation during that time is thought to have been equal to precipitation, and the residual lakes were reduced to the playa condition ; that is, the remnants of the gi-eat lake gathered in the lowest depressions of its basin were anmudl>- or occasionally evaporated to dryness, and their contained salts were precipitated, and either absorbed by the clays, etc., deposited at the same time, or buried beneath such mechanical deposits. This process may be observed in action in many of the valleys of Nevada in which ephemeral lakes occur. The broad, naked playas of Black Rock, Smoke Creek, and Carson deserts, as well as the level floors of the basins occupied by P>Tamid, "Wiii- nemueca, and Walker lakes, are in support of this livjiothesis. Should the lakes just mentioned be evaporated to dryness, playas would be left similar to those in neighboring valleys of less depth. It is beneath tlie level floors of these valleys and lake basins that the more soluble salts once dissolved in the waters of Lake Lahoutan are buried. Borings at certain locali- ties might reveal the presence of strata of various salts, l)ut in most eases they are probably disseminated through givat thick- nesses of clay, sand, and other mechanical sediments.

Analyses of the stratified beds laid down in tho basin of Lake Lahontan show that they are charged with saline matter to such an extent, that the total (juantity t>f the various solnl)le salts contained in them is certainly equal to, and probably in excess of, the calcareous tufa now ^^sible in tlie same depressions.

130 PRESENT .VXD EXTINCT L.\KES OF NEVADA.

The Organic Records. — The evidence derived from organic remains indicates that Lake Lahontau throughout its higher stages was never a strong saline or alkaline solution. Even during the abundant precipitation of dendritic tufa, the lake was inhabited by moUusks in great numbers, and was probably also the home of fishes of large size. During the thinolitic stage, when its waters were greatly concentrated by evaporation, the absence of fossils indicates that it was uninhabited by either fishes or mollusks.

SrMMARY OF THE HiSTORY OF Laio^: Lahontan. — The combined results of a somewhat extended study of the physical, chemical, organic, and other records left by Lake Lahontan, show that it furnishes a t^^iical illustration of the life history of an inclosed lake. The marked difference in the destiny of a lake that never finds an outlet, from the changes experienced by a normal lake, may be strikingly illustrated by contrasting the history of the Lahontan l)asin Avith that of a similar basin in a humid region which has been filled to overflowing, and been drained or filled, and transferred into a teiTaced valley.

Lake Lahontan began with the expansion of several i>laya lakes in the lowest depressions of its composite basin. These rose, with many fluctuations, until they became imited, and continued to increase in depth and extent until the full expansion of the first maximum Avas reached. This growth was due to a climatic change which caused an increase in precipitation and an accom- panying decrease in evaporation. Glaciers existed on the higher portion of the Sierra Nevada and on some of the basin ranges to the east, and by their melting assisted in the flooding of adjacent valleys. Then came a time of aridity. The previously flooded valleys became as waterless as at present, and possibly were comiiletely desiccated. A second period of increased humid- ity caused the basin to be again partially filled. The waters rose 110 feet above the level of Pyramid Lake, and the thinolitic tufa was precipitated from it. The character of this deposit indi- cates that a chemical change had taken place in the lake water. What this change was is not clearly landerstood.

After the crystallization of thinolite had gone on for a long period, the lake rose 210 feet, or to within 280 feet of its first maximum; and the heaviest of all the tufa deposits, the den- dritic variety, was precipitated. Aftei- the greater part of this variety of tufa had been formed, the lake continued to rise, and

LIFE HISTOKY OF LAKE LAHONTAN. I'M

at length reached au horizon 30 feet higher than at the time of its first great expansion. At the highest stage the water lin- gered but a short time, and no chemical precii)itates remain to record it. Two terraces, or, in other localities, two emhaiik- meuts of gravel resting on the lithoid terrace, were formed dur- ing this second rise. An increase in depth after the deposi- tion of the major part of the dendritic tufa is showu by the presence of fine mechanical sediments resting on it.

The recession of the waters after the second rise brought all portions of the basin previously sul)merged within the reach of waves and currents, and the sheathings of tufa were in part cut away, and their fragments liuilt into embankments and terraces.

The waters continued to fall, with many fluctuations, until the basin was completely dry. All of the salts not previously preciiaitated were dejiosited as desiccation advanced, and became buried or absorbed by playa clays.

The duration of the post-Lahontan period of desiccation is unknown, but judging from the length of time that would 1)6 required for Pyramid, Wiuuemucca, and Walker lakes to ac- quire their present degree of salinity under existing conditions, it must have closed about three hundred years since.

Throughout its entire history the lake underwent a nuiltitude of minor oscillations. These are imperfectly recorded by a large number of indefinite terraces, and by a nuiltitude of narrow bands of varying structure in the tufa deposit.

The main featvu-es in the fluctuations of Lake Lahontan coin- cide in a remai'kable way with the history of Lake Bonneville, and show that the climatic changes to which they were due were not local. It is assumed, for what seem valid I'easons, that the two high-water stages recorded in each of these lakes were synchronous with two periods of ice extension over nortlu'astern North America during the glacier period. If this correlatit)n proves to be well founded, — and at present there is no reason to doubt its validity, — it will show a still wider extent in the cli- matic changes that have affected the lakes of Nevada.

Intekpketation of the Records in Tekms of Climate. — In regions where the mean animal rainfall on a given area exceeds the mean anniial evaporation, it js manifest that an in- closed lake cannot long exist. No matter how deep the basin, it nmst ultimately bo filled to overflowing. The study of the pres- ent geography of the earth shows, that, in regions where the

132 PRESENT AND EXTINCT LAKES OF NEVADA.

lueau auuual precipitatiou exceeds about twenty or perhaps twenty-five iuches, iuelosed lakes do uot occur, although the topographic conditions may be favorable.

These and other considei-ations lead to the conclusion that the cliniatie changes which led to the flooding of the Lahontan basin, but did nut permit its l)ecoming tilled to overflowing, were not accompanied by heavy rainfall ; and that the mean annual pre- cipitation throughout its history was less than twenty or twenty- five inches.

Remembering that the principal streams flowing to Lake Lahontan came from the high mountains on its western bor- der, and that at the time of its greatest expansion its water sur- face was less than one quarter of its catchment area, and also that evaporation probably decreased as the rainfall increased, it seems safe to assume that the average rainfall over Nevada at the time it was transformed into a lake region was probably not in excess of ten or fifteen inches a year.

Considering the question of humidity alone, the times of marked expansion in the ancient lakes of the Great Basin indi- cate an increase in mean annual precipitation, and times of con- tracted water surface a decrease in rainfall. Thus interpreted, we have two periods of increased rainfall and of relatively great humidity, separated by an inter-lacustral arid period. The first period of precipitation was preceded by an arid period; and a similar period succeeded the last rise, and continues to the pres- ent day.

The sediments of lakes more ancient than those just described, and containing the bones of many extinct animals and the leaves of a luxuriant flora, also occur in Nevada ; but of this older chap- ter in the earth's histoiy, space will not pei-niit me to speak.

BOOKS OF REFERENCE.

Kixc, Clarence. Fnited States Geological Exploiatiou of the Fortieth Parallel,

vol. i. 1878, pp. 459-529. GiLBEKT, G. K. Lake Bonneville (Monograph, vol. i. 1890, U. S. Geological Survey). Russell, I. C. Lake Laliontan (Monograph, vol. xi. 1885, U. S. Geological Survey).

Quaternary Histoi-y of Mono Valley, California (8fh Annnal Report, U. S.

Geological Survey, 1886-87, pji. 261-394). '

Geological Reconnaissance in Southern Oregon (4th .\nnnal Report, U. S.

Geological Sun-ey. 18S2-83, pp. 4.31-464).

Geological Reconnaissance in Central Washington (Bulletin Xo. 108, 1893.

U. S. Geological Survey).

PLATE I

I

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"LATE III.

BEACHES AND TIDAL MARSHES OF THE ATLANTIC COAST.

By N. S. Shaler.

Introduction. — The essence of luodern science, the quality which the beginner in its study needs above all else to master, is the habit of patiently seeking to disentangle the maze of na- ture, so that he may be able to trace the orderly associations of events in what seems, to the ordinary view iit least, a i)icture.sque jumble of unrelated facts. To do this task in an effective way, the student should take up some class of actions in which he niaj^ trace the phenomena from one step of their growth to another, until he sees how they fit into the system of this earth. For such a task there is perhaps no matter which better lends itself to his needs than that of beaches. The features with which we here have to deal are tolerably well exhibited on a greater or less scale in all parts of the world which are not actual deserts. Thej^ are traceable along the shores of tiny pools and rivulets; niajiy of them are nearly as well shown in the snudler as in the larger examples; and certain of the more important of them can be more easily studied in the instances afforded by an artificial pool than on the shores of the ocean. In these little examples we may behold in a very limited compass many of the i)rocesses by which the land was formed and destroyed, or 'rather, we should say, made over, })y the ceaselessly acting agents which change the shape of the earth's surface.

To obtain the first preliminary notion of what a beach means, the student should choose some place on the margin of the sea, or, better, on the shores of a pond or rivei-, where soft materials, such as beds of sand and gravel, are subjected to the action of

(Copyright, 1895, by America'ii Book Company.) 137

138 BEACHES .VXD TIDAL MAHSHES.

the waves. Selecting a time when tlie wind is blowing toward the shore, he may note that the waves strike the bank with a certain anioimt of force, and that the incoherent rocky matter crumbles under their action. Partly by the stroke of the waves, and partly by the dissohdng effect of the water, the earthy ma- terial slips down the cliff, and is usually distributed over a gentle slope extending downward and outward from its base. In this simple group of facts we see the leading princijiles of beach action, which is, that materials which are brought into a water basin are so arranged that they tend to form a sloping mass of debris, the higher part of the incline being next the cliff. We may indeed define a beach as a mass of detritus which has been brought into its jwsition by the operation of waves, more or less assisted in their work by current action. As we shall see, how- ever, this general statement has to be extended and qualified, in order that it may be made to fit the numberless special groups of l)eaches which the varied conditions of this world bring about. The student of beach jihenomeua may well 1 tegin his observa- tions with the conditions which he will find set before him in the little rivulets in which are first gathered the waters of a river system. This field of action is particularly well fitted to show the relation of beaches to the other work which is done by the agency of water. In all head-water streams it is easy to see how rock materials, worn away from their bed places by the action of frost and the other agents of decay, are brought, at times of hea^■y i"ain, to the channels of the streams, and thus placed where they may be borne gradually downward to the ocean. Watching any one of these rivulets when it is swollen by the rainfall, we readily note that in the middle of the channel, where the water is deepest, the debris moves along with much gi'eater rapidity than it does in the shallowei- portions of the current next the banks, and that the fragments which are traveling in this central part of the streamlet are generally much larger than those which are in the part of the jirocession near the shore. ^Miere the brook is perhaps ten feet wide and three feet deep in the middle, shallo\ving gradually toward the banks, the deeper water carries onward pebbles several inches in diameter, or, if the bed be steej), it may urge forward bowlders a foot or two in cross section ; yet toward the sides of the torrent, where the depth is only three or four inches, the stream is seen to carry only small pebbles, while in the shallowest fringe of water

RIVER BEACHES. 139

nothing but the flue saud is in motiou. As this ditt'ereuce iu the energy of stream action is not only curious, but of gi-eat consequence in the history of the earth, we must look closely to its origin and effects.

It is well known that bodies weigh less in water or other fluids than in the air. This buoyancy, as it is called, is what causes wood or even porous stone, as pumice, to float. A sim- ple experiment of this principle can be made by lifting a stone with the hand out of a basin of water. As long as it is sub- merged it weighs much less than it does when it is above the level of the fluid. The result of this is that all rock material is much more easily truufUed along the stream beds than in the open air. Next we have to note the fact that the downward shoving power of water increases at a singularly rapid rate witli the acceleration of its speed. Therefore the speed with wliicli water moves, profoundly affects the value of the work wliidi it can perform.

We have now to note that the velocity with wliich a current or stream of water moves depends in a very important and im- mediate way on its depth, which depth determines the retarding effects of the friction of the fluid on its bottom. Returning to the case of the brook, we readily perceive that the stream is flowing several times as fast in its middle part, where the water is deep, as next the shore, where it is shallow. A closer study will show that the speed of motion is directly proportional to the depth, and that the current is everywhere swifter on or near the surface than it is next the bottom.

River Beaches. — We are now in a position to see liow river beaches are formed and maintained by the action of the running water. The detritus which, especially in times of heavy i-ain, is swept into these channels from the steep hillsides, journeys on as best it may in the varying conditions of the current. The larger stones generally keep in the deeper part of the water, being led there by the sloping sides of the channel. Tlie fine stuff" is often whirled by the eddies into the shallow parts next the banks, into poi-tions of the bed where, because of the friction which the current encounters in moving over the bottom, the flow is less speedy. Attaining a depth wliei-e the little waves which the winds create can affect tliem, the particles of sand and gi-avel are at once ai'ranged in the form of a beach ; that is, in the gently curved slope, witli its higher part lying against

140 BEACHES AXD TIDAL MARSHES.

the banks which confine the water. In the production of this beach the principles which regulate ciu-rent movements, and the transportation of the sediments that they carry, again control the action. To see how this is effected, we must now attend to the ciu'ious movements which take place in wave motion. Al- though it is easiest to study the features of waves on the shore of a large expanse of water, a great lake or the ocean, all that we now need in the way of information may be had by closely observing the wavelets of a brook or small river, which ai'e formed when a strong wind is lilowiug across the water. By noting the motion f)f any floating bits of wood, we pei'ceive that the wave is an undulation of the water essentially like that we see in a sheet of cloth when it is shaken by the hand or by the wind ; in other words, the wave moves on, though the particles of matter tkrough which it passes do not go forward. When the water is, say, ten times as deep as the wave is high, it sweeps over the Ijottom A\-ithout much effect ; but when the water is rela- tively shallow, it sets the finer gi-ains of sand in motion in the direction in which it is traveling, each wave bobbing them along for a short distance as it passes by. As the undulation comes into shoaler water, it rubs upon the bottom with energy, which increases with the shoaling ; so that next the shore it commonly has sufficient power to drag a good deal of sand with it. In this manner the greater part of the sand of river beaches is taken from the deeper parts of the stream and carried against the shore.

Some parts of the sand of river beaches are swung out of the channel by eddies. Those whirling motions of the waters tend to throw sand or even light pebbles to then* borders, and so bring detritus against the bank or into shallow water, where the waves may be able to move it. Again, in the banks of the lai'ger streams there is commoidy a mass of alluviinu or debris which the river has at former times brought down and built into a plain, through which the stream now wandei's. We may readily see that this ])lain is generally forming on one side, and cutting away on the other. As the bank is undermined on the wasting side, the sand and gravel which are given to the stream are generally built for a time into a beach a little way below the point where they are committed to the current.

It is characteristic of the sand in river beaches, as we shall find it to be also of that in sea beaches in general, that it is

SEA AND LAKE BEACHES. 1-H

usually in tolerably constant motion, the particles .iourneying slowly downstream. Each time the waves stir the gi'ains of sand, the latter move a little distance on their way to the sea. At everj^ season of floods, the deposit, being covered by deep and swift-moving water, is destroyed or gi-eatly diminished in mass, to be again developed when for a cousideraljle period the water re)nains at neai-ly one level. In fact, all the debris in a brook or river is normally in a condition of downward movement, which is only for a time interrupted by low water, when for a season the stream takes on a character of separate pool-like areas of water separated from each other by rapids. It is dm'ing these periods of relative stagnation of the current, when each pool is much like a small sea, that distinct beaches are formed. Their presence, indeed, may be taken as an indication that the river is at its low stage of flow. Imperfect and temjiorary as are the beaches beside the streams, they serve to show the usual condi- tions of contact of land and water, so that the student who is denied access to the nobler instances of such structures on the margins of the seas or lakes may well use them for his inquiries.

Sea AND Lake Beaches. — Turning from the rivers, where the beaches are only incidental phenomena in the work of water, we shall now consider the shore work in the seas and lakes, where those features are almost everywhere to be noted. In these basins, where the water, except for the swing of the tides, com- monly remains without appreciable change of level for centm-ies or for thousands of years, thei'e has usually been time for debris to gather along the shores in such (juantities that it attords the foundation for a beach. Here and there along the coast we find where the land, having been cai'ved into steeps by the action of streams or glaciers, has then by a downsinking process ])ecn brought below the sea level at so recent a. period that the de- struction of the cliffs aided ])y the action of the waves has not yet sufficed to fill the sea at .their base so as to form a beach. Again it happens, jiarticularly about the North Atlantic, that the glaciers of the last ice time swept far out to sea beyond the shore line, destroying the ancient beaches; so that when the frozen waters melted, the sea level came again against steeps, forming deep water at their base. That this is an exceptional, indeed we may say a temporary, condition of the contact of sea and land, — one which is everywhere in process of being over-

142 BEACHES AND TIDAL MAKSHES.

come, — can i-eadily be seen by any one who will watch such a shore during a time of heavy' storm.

Approaching in a time of storm a rock-bound coast, where the cliffs descend into deep water, the observer may, from some projecting headland, look along the shore so as to behold the majestic spectacle which the surges afford as they nish against the shore. Four or live times a minute the waves, having a height of maybe twenty or thirty feet, charge against the ram- part, and break into spray and foam as they meet the steep. Where the rock is tirm-set and smooth, the blows have no dis- tinct ett"ect; but wherever there is a weak place in the defenses, the waves have hollowed out a recess, which may be a consider- able cave, into which the swift-moving water i-ushes with a fury which is intensified by the narrowing space of the channel. In such a recess the waves generally find some bits of stone, which they swing against the walls, thus deepening and widening the recess. In time the overhanging rock falls down, thus serving to shallow the water at the base of the cliffs. This quarrying work is aided by the action of frost and other agents of decay, which are constantly at work on the face and summit of the precipices. Each year a quantity of debris is added to the heap which lies imder the water. In this accumulation of rocky mat- ter there enters a large amount of organic waste, the hard ]>arts left at the death of various shell-bearing animals, such as abound on the bottom of the sea near the land. In this way a steeply sloping mass is built up, which in time has its upper part so near the surface of the water that the fragments of which it is com- posed may be moved by the waves.

When the submarine talus at the foot of an ocean cliff has attained an elevation which permits the waves effectively to act upon it, a true beach is speedily formed. As soon as the masses of stone are in a position to be tossed about by the surges, thej^ are thrown in times of storm against the base of the cliff. We may often hear the sound of the blows thej- deliver, adding a harsh, crashing note to the roar of the breakers. The effect of this work is soon marked in tlie I'ounded form of the stones and in the excavation whicli has l)een made as a continuous indentation at the foot of the cliffs which thus are nuuU' to ovei'hang. In this condition the destruction of the hardest and firmest kind of rocks goes on at a rapid rate, for gi-a\ity now aids the other powers of waste in a most eft'octi\-o mannor. From

EOLLING BEACHES. 143

time to time masses from the jutting face fall to the level of the sea. Geuerally, in falling, they bi-eak into bits small enough to be tossed about by the greater waves, and so in time serve as battering instruments for the further assault of the land. The complexity of this erosive work is gi-eat (a volume could be writ- ten about it); but enough has 1)een said to show how effectively the land may be worn when there is a chance for the waves to hurl stones against its steep seaward faces.

Rolling Beaches. — As the further construction of the young beach proceeds, the mass of debris widens, and its slope to the seaward becomes more gentle, until it finally forms a rather wide strand having a slope of not more than ten degrees' decliv- ity. Wliere the sea floor was originally level up to tlie liase of the crags, there is now a talus slojjing from the level of the high tide to the distance of, it may be, half a mile outward. As this talus gains in wndth, it serves to protect the cliffs against the blows of the waves. Only those of gi-eater storms now attack the fii'm rock; the surges of ordinary times spend their forces on the bowldery and pebbly matter. At this stage the accumula- tion of detritus, or at least the ui>per part of it, becomes a rdl- ing hcac]i, — a curious and most important mill, in which stone is ground to the state of sand and mud.

If the student desires to see the rolling beaches in operation, he must visit the shore when there is a strong wind l)lowing upon the coast. An inspection made in good weather will not give the desired lesson, for the light waves of such a time do not suffice to set the mill in motion. When the seas break with their fi'dnts ten feet oi- imn-o in height, they strike a. ]>lo\v strong enough to send to and fro rounded fragments of rock which are three or four feet in diameter. With the advance of the waves these bowlders are driven up the beach. If the seas are powerful enough, the pebbles may be dashed against the cliff whence they came ; more often they roll up and down until they are worn out. In times of stonn the stones of a rolling lieach, sometimes to the depth of two or three feet, are carried to and fro with the advance and retreat of the waves. In tliis move- ment the bits roll over one anothtM- inuch in the maimer of mill- stones. The softer are rajiidly ground to the state of sand or mild, in which state the waste is readily cai-ried away by the currents to the open sea.

Although a large part of the pebbles which are found on

144 BEACHES AND TIDAL MARSHES.

any bowlder beach have made their way along the shore from promontories where the fragments are broken off bj^ the waves, another and perhaps more considerable part of these stones is brought in from the sea bottom by the action of various marine plants. Wherever the sea floor next the shore and in shallow water is strewn with pebbles derived from ancient glaciers, or perhaps formed on beaches which now lie below the smface of the water, seaweed becomes attached to these fragments of rock, finding their surfaces convenient places on which to fix its rootlike attachments. Almost all these species are provided with air vesicles, which serve to keep their stems and branches upi'ight : therefore when they become large, they exercise a cer- tain inilliug action on the stones ; and the waves, as they pass by, pull upon the smfaces of the plant. The result is that in time of storm the stone is lifted above the bottom and borne toward the beach. A few strokes of the waves serve to detach the plant, after which the pebble becomes a part of the rolling beach, whereon it is in time gi'ound to powder.

Many of the pebbly beaches in New England are entirely sup- plied by the action of seaweeds ; and one small island near the coast of Cape Ann, which is no more than a rolling beach washed by the waves, appears to be maintained by the constant importa- tion of pebbles which are plucked from the bottom in the man- ner above described. The same process, with shells taking the place of pebbles, may be traced along the sandy shores of all the continents. In fact, the gi-eater part of the shells found on some of the Atlantic sand beaches which have been studied by the writer owe their transportation from the bottom to the strand to the action of seaweeds, or, in some cases, to the similar effect exercised by the growth of plant-like animals, such as sertiilarians, which have become attached to the hard parts of the mollusks.

Action of Wa\ts and Tides in the Foemation of Beaches. — The energy of the sun sets the air in motion, and the wind causes the waves, so that it is solar force which is imparted to the waves. Moving over the deejier parts of the sea, these undu- lations have probably no effect on the bottom. As the wave comes nearer the shore, and enters the shallowest parts of the sea, it begins to drag on the bottom. This action is not considerable until the depth is less than two hundred feet, where the ordinarily great wave is com]»etpnt to move sand up the slope toward the shore. As the water still further shaUows, the scraping movement

ACTION OF WAVES AND TIDES. 145

increases, until it can move at fii'st the smaller pebbles, and at last the bowlders of great weight. The result of this action is that the waves which roll on a shore are effective in moving frag- ments from a considerable depth to the strand. If this were the only source of motion along the coast, the effect would be to heap up a great mass of debris at about the level of high tide. There are, however, as we shall now see, many other influences at work which have a large share in determining the form of a beach.

Moving over the deep sea, a wave proceeds as an oscillation or wrinkle of the water, which is substantially, as before noted, like the undulations of a shaken cloth. Oidyin a verj' small measure does the water go forward in the direction iu which the wave is moving. When,, however, the surge comes into shallow water, its form and the character of its motion undei'go important changes, which progress with the shoaling. The wave shortens up, becoming relatively higher and steepei' ; it also i)n- parts a stronger forward movement to the water. The shorten- ing and steepening of the wave is brought about in the following manner : Coming ever into shallower water as it nears the shore, the surge finds the friction due to the bottom greatest iu its front part : this part is therefore proportionately more retarded than the following portion of the swell, Avhich thus tends to overtake the front. As water is practically imcompressible, the wave has to increase in height. This principle, which is called the conser- vation of areas, can well be illustrated by flexing a piece of paper, pushing the arch over a table, and shortening the base as it nears an imaginary shore line.

An interesting cooperative work in the action of waves iind tides is effected throiigli a peculiar movement of the sea known as the undertow. AVlien the waves roll heavily in upon a shelving coast, a considerable amount of water contained in the upper part of the surges moves in upon the shore more rapidly than that m the under part of the wave. This incoming water, having to escape eventually seaward, finds its way out along the bottom. Those who are accustomed to swim along the coast where the bottom is shallow, and at times wIkmi the surf is heavy, have often found themselves drawn away from the land by this un- dercurrent. It may well be noted that the stream never affects the upper two feet or so of the sea, and rarely has strength save below the level of three feet. Thus a swimmer wlio takes pains

146 BEACHES AND TIDAL MAKSHES.

iu his movements that no part of his body is deeply immersed can readily make his way baok to the land.

The eli'eet of the imdertow, which is strongest when the waves are attacking the shore -svith the greatest energy, is to draw the line sediments away from the immediate coast line, brin<ring the detritus far enough out to sea for it to be taken by the tidal cur- rents, which convey it, it may be, for many miles away from the coast line.

If a wave suffered no other change as it approached a shore save that due to the shortening of its width, the result would be the formation of surges of vast height, which would strike upon the coast line with many times the energy which they actually possess. The fact is, that as soon as the wave arrives in water sufficiently shallow to hinder its forward motion, and thus to bring about the increase in height, the friction which it encoun- ters progressively tends to exhaust the euergj- which is stored iu the undulation. In the existing conditions of our coast lines, probably the greater pait of the enei-gy of the waves is applied to the bottom of the shallows which they traverse before they attain the beaches or cliffs. In these shallows they impel the detritus up the slope, and cast it upon the shore. If this action were not opposed by the work of the tides, the effect would be to gi-eatly increase the amount of sand and fine i)ebbles which we find at the contact of sea and laud; but the work of the tidal oscillation is distinctly to hinder and limit the invasion of sand from the continental shelf.

As the tidal wave rushes in ui;>on a coast, it has, when it comes from the deejier sea, a rate of advance of several hundred miles per hour; but, owing to the slight amount of elevation which it gives to the waters, it exercises at first only a small dragging power on the detritus of the ocean floor. The nearer it comes to the shore, the gi'eater this dragging action, because of the shallowing of the water; but the effect is rarely gi-eat enoiigh to move more than coarse sand or small pebbles. As the tide comes toward the land, these movable fragments are carried up the slope which leads to the shore. As the tidal wave goes out, the bits journey away from the coast. It is easy to see that, as the movement takes place up and down the sloping floor of the sea, the effect will be to cany the sand and pebbles farther and farther from the shore, and this for the reason that they will move farther with a given tidal impulse in the direc-

ACTION OF THE A\TND. 147

tion in which the bottom inclines. In this way the tides, by dragging materials from the beaches and shallows toward the deep sea, serve ever to extend the continental shelf.

The action of waves and tides on the sands of the shallow waters, though in general of a contrasted nature, is not uniformly so. The surges act only in times when gales blow upon the coast; while the swingings of the water which are due to the attraction of sun and moon operate with something like uni- formity, varying only as these planetary bodies unite or oppose their influences at the periods of spring or neap tides. The general effect of these combined actions is to mak(^ tlie amount of sand which is gathered on any beach from time to time quite variable.

Action of the AVind in the Formation of Beaches. — There is yet another cause of much diversity in the amount of sand which we may find upon a beach. This is due to the action of the wind. So long as the debris along the coast is covered with water, the wind can act upon it only by means of the waves or currents whicli it induces in the fluid ; when, however, the sand is bared by the retreating tide, it (juickly di'ies, and in this state is easily moved about by the air streams when they have a con- siderable speed. Blowing upon the shore, the winds carry the sand, and even small pebbles, from the stretch of surface between high and low tides above and ])eyond the verge of the waters, usually accumulating the material in the heaps known as dioics. When the wind blows offshore, as it prevailingly does aloug the Atlantic coast of North America, it carries the dry sand back into the sea, where, if the conditions favor, it may be removed by the tidal and other currents to a distance from the land. In tills way tlie accumulations of sand on beaches along the east- ern coast of the United States are much restricted. Where the ])revailing winds come in upon shores which are bordered by sand beaches, sand dunes always abound. These accumulations are indeed accunite gnnges wf the averag(^ direction of the winds which are strong enough to move sand. In their slighter forms sand dunes are inconspicuous, but where they are well devel- oi)ed they afford some of the most striking features which are found at the contact line of sea and land. They are, moreover, in certain cases, of no small importance in the history of the shore lands. We shall thei-efore note some of their more im- portant features.

148 BEACHES AND TIDAL XIAKSHES.

Sand Dunes. — ^'hen the sand is driven up the slope of a beach to a point beyond the high-water level, it at once escapes from the field in which it was subjected to the forming and uni- forming actions which make the grains and dispose them on tlie smooth incline of the shore. When the wind-blown fragments come to the top of the beach, they encounter a relatively rough suiface on whicli there are usually abundant tussocks of rough gi-ass or of other plants ; these diminish the energj' of the wind, which on the more open shore had full sweep, and so serve to bring the grains of sand to rest. As soon as a little heap is thus formed, it affords a yet better shelter on its landward side, and so gives the essential conditions for the gi-owth of a dune. Thenceforth the jjrocess is very simple : the flying bits move up the seaward face of the mound, slip over its summit, and come to rest on the leeward face of the elevation. As the sand, even when it appears very barren, contains much food for plants, many species have become specially modified to suppoi't life in the difficult conditions which the dunes afford. The most of these plants belong in the groups of gi'asses, of which the well- known hench f/rass is the most widely distributed and best- known form. This interesting species has very long and strong- grooving roots, which enable it to seek a supply of water, as the plants have to do, at a gi'eat depth beloAv the surface. Its leaves are remarkably tough, and are thus fitted to withstand the rude ti-eatment of the storm winds. This plant, hke others of its kindred, but in a yet more efficient way, increases not only by its seed, but by means of runners or horizontally extended roots, which grow with such rapidity that they may extend for the distance of ten feet or moi*e in a year. From point to point these runners give off vertical shoots, which estal)lish the crown of a new plant ; these horizontally disposed roots also put forth a great number of fibrils, which enmesh the sand so as to make it difficult for the strongest blast to disturb the mass.

On account of the vegetation which occupies the top of a dune, a considerable store of the sand which is driveu upon the hiU is held upon the summit : the elevation thus gi-ows in height. This gi'owth may go on until the mass rises a hundred feet or more above the level of its base, while its width and length may be several times as great. As the conditions which determine the formation of these curious products of the l)eaches are pecul- iar and irregular, the slopes and arrangements of dune hUls at

m^

SAND DUNES. 149

first sight appear to be more disorderly than is the case with any other gi'oups of shore features. This apparently confused natui-e of dunes is in great part due to the fact that they alone, of all the elevations of the laud, have the singular habit of marching away from their point of origin, it may be for gi-eat distances across the country.

On the seaward side of the dune, because of the euergA- of the wind, at times when storms blow ripon the coast, the blast digs the dry sand from among the roots of the vegetation, and sends the uprooted plants and sand together over the top of the hill to its landward side. So rapidly does this jn-oct'ss go on, that in a single jirotracted gale a dune thirty feet high may be moved back from the shore for a distance of fifty feet or more. As the marching mass of sand journeys away from the coast, various causes serve to resti-ain its movement. It is e\-er coming into districts where the air moves less swiftly. As the grains of sand decay, they begin to cement togethei-, — a process which dkectlj' hinders the work of the wind and favors the growth of plants: hence it comes about that the advance of a dune is gradually slowed, and in the end the dune comes to rest. Yet in some eases they have been observed to journey for as much as ten miles from the beaches next which they were formed. In some instances they have overwhelmed villages and desolated extensive tracts of fertile land.

It not infrequently happens that dunes of considerable size form on the shores of fresh-water lakes. Thus some of the most important of these wind-])lown hills in this country lie at the southern end of Lake Michigan. In such cases we always find that the sand is derived from the moving of beds of a sandy natui-e, which are broken up by the waves. In yet other and rarer instances, dunes foi-m along the 1)anks of rivers whei-e th(> alluvial cliffs are sufficiently sandy to afford a considerable supply of fine detritus to the winds. As these fluviatile dunes cannot ordina- rily go far before they enter fields thickly covered with vegeta- tion, they rarely wander more than a fi!W hundred feet before they become densely covered with plants, and so are bound down. Moreover-, in the constant swingings of river channels through their alluvial plains, — a movement which brings about a washing-over of all the deposits of those terraces in a brief geological time, — such dunes are apt to be destroyed before they attain any great size.

150 BEACHES AND TIDAL MAKSHES.

S.^JO) Beaches. — We must uow tuvn again to the develop- ment of sand beaches, and theu" rehition to the physiography of any shore. The first jjoint to be noted is that the beaches com- posed of sand are vastly more extensive than are those which are occupied by bowlders. On the Atlantic coast of the United States, which affords a fair gauge for a determina- tion as to the proportion of shore lines in general, the sand beaches probably oceujiy at least ten times as much of the sea front as those which are composed of pebbles. In pai-t this excess of sand on the shores is to be attributed to the fact that the rivers bring forth a certain amount of material; moreover, a considerable part of the fine-ground detritus which occuiiies the northern i)art of the continent owes its comminu- tion to the action of the glaciers which recently covered that land. The share of the marine agents in these materials has been limited to their transportation and arrangement. It is, however, evident that there are other important conditions which have affected the history of sand grains, and exerted a very great influence in promoting their resistance to the influences which lead to their decay, and thereby led to the accumulation of arenaceous matter along the sea border. These conditions must now be considered.

It should in the first place be noted, that ordinary sand con- sists normally of quartz crystals which have been split along their cleavage planes to the jioint where the fragments are no longer easily broken; next, that this substance is, of all the connnon minerals of our rocks, the one which is least readily affected by the agents of decay; moreover, it has a relatively low specific gl•a^dty, and is also very hard, so that when tossed al>out by the waves it does not strike with violence, and so is much less subjected to wearing than most other rocks. In ad- dition to these protective features, and much more important than they, is another and peculiar qualitj^ which sand acquires when it is com}>letely wetted. In this state the gTains lying with their faces against one another hold the water between them in a manner which makes it nearly impossible to force the neigh- boring surfaces together. This can be readily seen l)y apj>lying pressure to wetted sand. Such force serves to squeeze out a portion of the water ; but, even when applied at the rate of a thousand pounds to the square foot, there remains enough of tiie fluid between the grains of sand to keep them somewhat

BAKKIER BEACHES. ■ 151

apart, aud thus to prevent the most effective friction of the faces upon one another.

To the action of cajiilhiry attraction, as above descrihcil, is due the fact, that, when tlic division of rock materials to the state of sand is brought about, all or nearly all the erosion due to the beating of the fragments togetlier ceases. Some wearing is accomplished when the grains are caught between pebbles, and so come between upper and nether millstones. A certain though small and slow decay is brought about by chemical ac- tion; l)ut in general the sand, while it is in the sea, is singularly well preserved fi'om injury. We can the better note the meas- ure of this preservation by observing what happens to the sand which comes into the possession of the wind. In this condition there is nothing to keep the grains apai't. They wear rapidly, though they receive no such blows as are delivered on the beach by the surf. In the coui'se of a few miles of journey the sand in the dunes is more worn than that which has inoved for, it may be, a thousand miles along the shore. Thus the sand of northern Florida, which has traveled southward from the region beyond Cape Hatteras, is not more roimded than much which is in the inner or landward dunes of the coast within sound of the ocean waves.

The result of the protection against wearing which is afforded to sand gi'ains by the water which surrounds them in the sea is of very great consequence in the history of the lands. As before remarked, l)y far the greater part of the marine shore lines are bordered by sands. Probably, the world a])out, over nine tenths of coasts are fringed by such beaches, composed of practically indestructil)lo materials. Upon these bounds the ocean waves, which, when armed with pebbles, can successfully assail the hardest rock cliffs, l>reak without effecit. Were it not for these indestructible shields, the waves would long ago have reduced the land areas to much smaller proportion than they now exhil)it.

Bamueh Beaches. — The function of sand beaches in defend- ing the land from the assault of the waves makes it interesting to note in more detail the ways in which these lieaches are formed and maintained along the continental shores. The easiest way in which to ajiproach this inquii-y is by supposing that the coastal region of the southern part of the United States should be elevated in a geologically smlden manner, so as to

152 BEACHES AND TID.Ui MAKSHES.

bring above the sea a part of the contiueutal shelf which is still covered by the oceau waters.

The immediate effect of elevating a seaboard region which is fringed by the characteristic shaUows of a continental shelf is to bring the surf line against an unprotected shore, so that it may attack it in a very effective way. So long as the waves are of ordinary height, they may break close in against the land, and their swash will proceed to cai'S'e out a cUff ; the rocky waste thus formed being drawn back by the reflux of the waves, and serving to shallow the water for some distance from the shore. This process of shoaling will also be favored by the action of the waves, which, as they approach the land, will drag, by the friction which they exercise upon the bottom, large quantities of sand in toward the coast line. TVheu the depth of the water has been thus considerably diminished, it will happen, in some great storm, when the waves have an unusual height, that they will break at a considerable distance from the land. The line of the surf may indeed be placed some miles away from the actual shore.

As soon as a line of breakers is formed, a number of condi- tions combine to bring about the formation of an elevation of the bottom at the point where the waves are overtui'ned. Each wave in succession drags a certain amount of sand with it, this detritus being laid down when the wave overturns and is thus broken up. In some cases it may come about that the upward gi-owth of this elevation takes place with such rapidity that in the course of a day or two, in which heavy seas prevail, the ele- vation may attain to near the surface of the water. If it hap- pen to rise from the level of the sea, the permanence of the barrier is at once assured; if it fall short of that height, the lesser waves of the following ordinary weather are likely to overrun the elevation, and to scour away a part of its height. But in some subsequent great storm, the waves in which, on account of their height, have to break along the shallow line, the ridge is pretty sure to be built above the water level. "Wlien- this height is attained, a portion of the sand brought in by the waves has a chance to become dry, and thus is easily moved by tlie wind. In this condition it is readily driven over the narrow ridge into the water of the lagoon which the barrier has formed, or it may accumulate in the form of dunes. As time goes on, the continued accessions of sand, drawn in from the sea bottom

. INLETS. 153

by the waves, serve to widen the barrier, which in the course of a few thousand years may gi-ow to the width of some miles.

" Inlets." — The barrier beach may, wlieu originally formed, have great continuity. Occasionally, where there hapjion to be strong headlands with deeper water off their faces, the Wall of the beach may come in contact with the land ; but, as it is shown by many instances, the narrow island of the reef may extend in continuous manner for the distance of hundreds of miles along the shore. Owing, however, to the fact that the barrier acts as a dam to hinder the land waters from taking their natural course to the sea, it is sure to be breached by outlets from point to point along its length. Such breaches are usually miscalled " inlets."

It is characteristic of those l)reaches which give exit to the river waters, that they are formed and closed in a somewhat curious manner. It may generally be observed that the open- ing forms near the point where the barrier joins the headland, and that year by year the opening moves along the si lore, the gap filling on the one side and cutting on the other, until it at- tains the next headland in its line of march. Then for a brief time, while the river waters bank up in the lagoon, the breach is closed, again to open at the point where, in the previous case, it was seen to begin. Tlie reason for this singular marcliing of the inlets on a barrier beach is to be found in the fact that along these sand walls the detrital materials joimiey in one direction, which is determined by the set of the current which sweeps the shore. Thus along the Atlantic coast from Cape Hatteras southward, and also, though in a less determined manner, on the more northern parts of that shore, there is a southward-setting current, which makes a gradual drift of sand all the way down to Cape Florida. Hence it comes about that the sands fill in on the northern side of the inlet, and force the waters continually to widen the exits on their south l)anks, — a process which com- pels the passage to move down tlie coast. As each headland somewhat oljstructs the southward march of the sands, the bar- rier beach is ai)t to remain lowest immediately south of where the ridge comes against the projecting part of the shore ; and so, when the inlet has to form again, the breach is apt to occur at that point, — the place where it originally formed.

The Lagoon or bay between the barrier beacli and the main- land, being originally shallow, and receiving accessions of detrital matter from the rivers, from the sand blown over the beacii, and

VA BEACHES AND TID.AX, MAKSHES.

from the accumulations of organic remains, is gradually brought into the condition of a swamp, through which wander the streams whieh convey the land waters to the open ocean. When this state is attained, the detritus borne down by the rivers is again deposited beyond the coast line, where it serves to aid in the sliallowiug process, which is likely in time to lead to the formation of yet another barrier beach. Even without the inter- vention of river sediment, the other agents which accumulate sediments on the sea floors are likely to bring about a measure of shoaling, which results in the formation of these successive sand reefs, in the manner above described.

Although the foregoing account as to the formation of beach barriers along shores which have the characteristic continental shelf, shoaling near the coast line, has been pre[)ared as a gen- eral statement, it may be taken as an account of the steps by whij?h the elongate sand islands whieh inclose the lagoons and l)ays of the region south of Cape Hatteras and north of Cape Florida, as well as those along the northern shores of the Gulf of Mexico and elsewhere, have been formed. By consulting the excellent Coast Survey maps of the Atlantic shore of the United States, the student may note the fact that there is an almost continuous water "way inclosed by these wave-made islands, extending in some cases for the distance of many hun- dred miles. Here and there the slightly higher parts of the land have formed capes with such a depth of water oft" their faces, that the barrier beach has been forced into contact with their shores; but so inconsiderable are these interrni>tii)ns, that a small })oat can, with infre(iuent jjovtages, )>e navigated from near Norfolk, Va., to Bay Biscayue, in southern Florida. It has indeed been proposed to develop this natnral water way into a ship canal, which would aft'ord a safe and easy route for vessels passing along this dangerous portion of the continental shores. __ CoEAL Beaches. — On certain portions of the ocean shores within the tropics, where a current of warm water, impelled by the trade winds, continuously moves in against the coast line, those species of polyp which dwell in communities, commonly known by the name of corals, are developed in a very plentiful way. These compound animals are common on the sea bottoms even in waters as far north as Cape Cod ; but only where the species of the group are nomnshed by warm currents, such as often flow in upon the shores and shallows of the seas which are warmed by

COKAL, BEACHES. 155

a nearly vertical sun, do these creatm-es gi'ow in sucli numbers and to such aggregate bulk, that they may form a coast line.

It is characteristic of coral beaches that nearly all the sand, or rather, we should say, the finely divided matter, of which they are formed, is composed of the skeletons or limestone framework which serves to supjiort the coral animals while they are in the living state. This material is mingled with the debris of shells, and often in large measure with the limestone coverings of the small Foruminifcra. While the corals are living, they are admi- ral)ly adjusted to the assault of the waves in such a mannei- that the sea is practically unable to damage their communities. It is only when a colony dies in whole or in part that the waves are fairly able to make use of its fragments in building a beach. In fact, beaches of this nature depend for their growth and nuiin- tenance almost entirely on the work of extracting limy nuitter from the sea, which the coral animals accomplish in a second- hand way l)y consuming marine plants or other animals which have fed upon that source of supjily.

The student who would obtain a clear notion of coral beaches should visit some shores of that description, such as may be found along the Keys of southern Florida or in the islands of the Bermudas. Selecting any poi'tion of the strand which faces the open sea, he will observe that the beach is covered by a layer of whitish powdery rock, the grains of which are more rounded, and generally more variable in size, than are the bits of ti'U(> sand of an ordinary shore. Carefully examining the material, he will perceive that, except that there is here and thei-e a bit of pumice or volcanic lava blown so full of bubbles that it becomes light enough to float, all the debris of the shores is of oi-ganic origin. On the landward side of the' beach he will commonly find a low cliff, cut either in the older part of the reef, which has been lifted up from the sea by the upward movement of the land, or in a dune-like accumulation composed of tiuy bits of coral which have V)lown in from the strand when it dries in the hot sun. Whetlior this part of the reef which is exposed to the air is dune or ele- vated bottom, it is always easy to note the fact that the rock material is exposed to a rapid solution by the rain water. The result is that the dunes never attain any great height; moreover, they never march far inland, in the manner of sand dunes, for the reason that the limestone grains speedily become consolidated into a tolerably firm-set rock.

;

156 BEACHES AXD TID.\1, MAKSHES.

Looking to the seaward at low tide, the observer may note in the hollows of the surf the protruding tops of the living coral communities, which never attain a height above the i)lane of ordinary low tide, and which serve to maintain the large supply of matter which is continually being gi'ound up by the action of the waves.

In most cases the coral shore lies upon a fringing reef, sepa- rated from the mainland by a shallow landlocked basin in which a host of frailer coral commimities and other delicate marine creatures develop. These landlocked forms afford a great deal of limestone sediment in the form of mud, which is carried out to the front of the beach by the tidal currents. In some cases the amount of this organic deliris is so large that it accumulates in the form of a considerable delta at the seaward end of the channels which connect the lagoons with the open water.

In the tropical oceans, and even in higher latitudes which are affected liy warm currents, coral islands frequentlj' abound which afford very interesting organic beaches. Islands of this nature are most abundant in the Pacific and Indian oceans, but they also occur in the Atlantic basin along the line of the eastern Antilles. Tliey constitute the Bahamas, the greater part of the islands or Keys of Florida, and the beautiful archipelago known as the Bermudas. These oceanic coral islands commonly have an annular or ringlike shape, inclosing a 1 )asin or lagoon. Some- times the ring is comj^osed of a single island, through which there is but one breach connecting the inner and outer water. In other instances the ring is formed l)y many small isles, with shallow water ways between them. Coral deposits of this form, known as atolls, present very beautiful beaches of organic rock, that on the outer side being wide, and the seat of a heavy grind- ing action which the waves inflict on the dead coral ; while the lieach bordering the lagoon, of which the shallow waters are rarely more than a mile or two in diameter, forms a delicate strand of no great width, for the reason that tlie waves have not nn;ch ])ower. From the oiiter beach the storm winds in dry weather sweep a good deal of powdered rock into rudely shapea dunes, which, being comi^osed of fertile earth, often support a luxuriant vegetation of palms and other tropical plants. The combinations of beaches, and their products the wind-made hills, make the atoU the most singular geographical feature of the tropical seas.

u

MARINE MARSHES. 157

It is chai-acteristic of coral beaches that the materials of which they are composed, unlike those of ordinary shores, are readily taken into solution, and in that state may be borne away by the currents to any distance.. As these reefs can only be found where ocean currents moving with considerable velocity come in contact with shallows or shores, the water which bathes them is always in motion, and so bears off the dissolved matter. Notwithstanding the constant robljery of their matei-ials, which is effected by the solving process, the coral beaches often widen with great rapidity ; the contributions of their debris which are made to the ocean floor are great in quantity as well as widely distributed; and the powdei-ed waste which is blown to the landward by the winds is often sufficient to cover consideral)le extents of country.

A capital instance showing the constnicting efficiency of reef- building corals may be seen in southern Florida, where the outer or southward third of the great promontory owes its construction to the development of successive fringes of coral gi'owth on the beaches formed of the debris of these reefs, and of the detrital matter blown from the beaches into the shallows between them and the mainland.

Marine Marshes. — Closely related to the work which is effected by coral reefs is the organic result accomplished by other groups of living beings along all the shores of the world. We have already noted the fact that in the beach the results of marine action lead to the construction of a broad, gently sloping shelf, extending from the shore to a considerable depth of water. This slightly declining part of the sea floor affords an admirable site for the development of a great array of species both of ani- mals and plants. Owing to the shallowness of the water, a share of the sunlight passes through the fluid to the liottom. The grinding action which takes place in the waves bi'ings much mineral matter and organic material into the condition where it readily becomes fit to support the species which dwell in these shoals. The undertow and other currents transport this suste- nance to the waiting throng of lieings. In these and other ways the undersea portion of the beach becomes, of all the water- covered areas, the fittest seat of life.

Where, as is the case on most sandy shores, and also behind those coral reefs which fringe the mainlands, there are inclosed areas of shallow water, we find another realm extremely well

158 BEACHES AND TIDAL MARSHES.

suited to organic development. As before noted in the case of coral-reef lagoons, these embayed waters are admirably suited to the gi-owth of marine species. Among the animals, the bivalve Molluscii, particularly the oysters, find these sites very well suited to their needs. They often build deposits composed almost altogether of their shells, having a dejith of many feet, and a horizontal extension of many square miles in area. In these embayed waters many species of crustaceans flourish, and at their death give their skeletons to the accumulation which grad- ually shallows the water. In this manner the areas fenced in by barrier beaches become floored with sediments, which, so far as their chemical composition is concerned, are admirably fitted for agricultural purposes. A large part of the fertile land of Hol- land has been won to tillage by completing the natui-al beach barriers which separate the fertile ground from the sea, the water from the fields being removed by pumps.

When the lagoons behind the sand beaches have become shal- lowed to the dej^th of ten or twenty feet, certain low-grade flower- ing plants, mostly of grasslike form, begin to convert the areas into manne marshes, — wide savannas which are covered bj' the sea for but an hour or two a day, during the time of high tide. The process by which the marsh growth takes place is very interesting.

A number of land plants have modified their original specific characteristics so that they are enabled to dwell in contact with or even under the sea, the salts of which are deadh' to almost all vegetable species. Among these, the most interesting is that known as the eel grass, which, though a fiowei-ing plant, never lifts its form above the surface of the water. This species will take root in the embayed waters wherever the bottom is soft, and less than twelve feet in depth at low tide. Within the close-set stems dwell a host of marine creatures; moreover, the network en- tangles drifting sediments; the two actions — that arising from the death of organic life, and that from the floating debris which is caught, and brought to the bottom — serving rapidly to shoal the bottom of the lagoon. A number of other plants, mostly grasslike forms, begin to grow on the nuid flats formed between the eel-grass banks and the shore. These species, which require to be above the water level for the most of the day, produce a very dense mat of vegetation bj' weaving their tough roots to- gether, thus forming a mass which only heavy waves can break

MAKINE MARSHES. 139

up. lu this manner the construction of the marine marsh is begun around the margins of the water field.

When the waters inclosed Ly a barrier Vjeach have been brought into the state of a marine niarsli, the area can, as experience shows, in most cases be readily won to the uses of agriculture. Wherever the rise and fall of the tide is eight feet or more, it is possible so to arrange dams, at the point where the sea water enters, that the level of tlu^ marsh may be kept permanently above the sea; then, by means of appropriate ditchings, and by removing the tough mat of grass and roots, rich and very enduring soils are made ready for tillage. Exper- iments made on the coasts of New England and elsewhere show that lands thus won from the sea are fitted to a great range of crops, and can be tilled for many years without reijuii-ing mani;ring.

Where the tides rise to a gi-eat height, as in the region about the Bay of Fundj', the strong currents created by the watei-s which enter and leave the embaymeut sweep with them g)-eat (piantities of mud. In such regions the people have learned to constnict artificial dams separating the mud flats from the sea, the barriers being provided with openings for the passage of the tidal waters. These waters, entering the artificial lagoons laden with sediment, are retained in the area until they have laid down their burden. When, by this process of deposition, the bottom of the inclosed space has been brought to near high-tide mai-k, the sea is barred out, and the new-made land is ditched and brought into the con- dition of profitable fields.

Although in this country the long-continued abvmdance of good land on the frontiers, which might be had almost for the asking, has kept peoj^le from paying much attention to the class of lands which have afforded the agricultural wealth of Holland, the time is soon coming when the mai'ine marshes formed behind the barrier beaches along the Atlantic coast will be brought into condition to serve the uses of man. It seems likely that somewhere near twenty thousand square miles of extremely fertile soil will thus be gained to the service of our people when they have applied the methods of im]irovement which have been so successfulh' followed in the districts about the mouth of the Khine.

Although the grasslike plants do the most of the work of win- ning the shallows from the sea in the manner above described, a

160 BEACHES AND TIDAL MARSHES.

similar end is effected in the tropical parts of the world by the growth of the peculiar group of trees kuowu as jiianffrores. All other forms of arboreal vegetation except the uiaugroves are imable to tolerate auy considerable contact with sea water ; but these trees, of which there are a number of species in different parts of the world, have varied their habits and their structure in a remarkable way, and have thus become competent to meet the peculiar conditions which they have to encounter in the lagoon behind the barrier reefs formed by the coral or sand beaches of warm regions. Beginning on the shore, the mangrove establishes its 'crown above the level of high tide. From this crown or junction point of stem and roots there extend off toward the sea long runner-like jiroeesses, which grow down- ward into the water until they attain the bottom, and there take root. From the upper part of these runners new stems arise; and the process may be continued until wide lagoons become covered with a low, dense forest, beneath which the tide may ebb and flow until the falling leaves and twigs, together with the remains of animals, have filled up the interspaces. In this way the mangroves win to the conditions of marsh great areas of embayed waters, and thus complete the work of barring out the sea which is begun in the formation of barrier beaches.

The foregoing paragrajjlis may serve to indieat(> in a general way something of tlie more important work in relation to or- ganic life which is brought about through the growth of beaches and the work which is done upon them. This work consists in part in the formation of shallows next the shore, which afford a favorable site for the development of living forms ; in the grind- ing-up of organic waste to a state in which it can readily be transported liy the waters to the creatures which it is to feed; and in the development of extensive shallow landlocked basins, which by their conditions favor the growth of a great range of animals and plants. Having thus traced in outline the inore im- portant relations of beaches, we must now turn our attention to certain detailed features in these structures and their distribution.

Composition of Sand Be.\ches. — It should be noted, that, while sand beaches are extensively developed along the shores of all the continents, they rarely appear in anything l)ut the most attenuated form on the smaller islands which exist at dis- tances of more than a few miles from the shore, or which are surrounded by deep water. On such insular lands the ground-

COMPOSITION OF SAXD BEACHES. 161

Up rock waste which goes to form sand beaches is likely to be swept away from the shores, the amount remaining being insuf- ficient to aflford characteristic beaches of this nature. On the seaward faces of the continent the long-continued shoivs afford an opportunity for the arenaceous material to journey for great distances, and to be accumulated on those portions of the coast toward which it is impelled by the prevailing direction of the wind and the current. Thus on the eastern coast of North America the sand derived from the wearing of the cliff or bluff shores which are wasting under the action of the sea (as those along the coast of New Jersey) journeys southward for a great distance. It is impelled in this direction because the average direction in which the waves nm in from the sea is from the east, while the trend of the shore is southwesterly. The result is that the sands march down the shore, impelled by a current which is inflected to the south by the trend of the shore.

The reader can by a simple experiment illustrate the manner in which such a current is formed. Taking an ordinary l^asin of water, the breath from the lips can be used to form wavelets, which may be made to break against a straight-edged 1)ai-rit>r. Using small floats, it can be noted that the resulting current sets down the barrier in the direction in which it inclines; that is, on the side of the obtuse angle between the axis of the air stream and the resulting waves and the opjiosiug margin.

In its journeys down the long coast between Long Island, New York, and Florida, the moving sand, where it passes the mouth of a considerable river, is i>retty siu'e to be thrust for a distance out to sea on the continental shelf. From this excursion to the seaward it is, howevei", returned by the action of the waves, and so comes again to the shore, or the verj' shallow water next it, and is thus free to go farther to the southward. As both the eastern and western shores of North America exten<l obliquely to the run of the waves, which come on the one side from the east and on the otlicr side from tlie west, there is a-ii evi- dent tendency on both the Atlantic and Pacific coasts for the sands to work to the soi;thward. This, liowever, is much more conspicuous on the eastern side of the continent.

We shall next consider some interesting details whicli may be here and there, though not continuously, obsei'ved along the beach lines wherever they are exhibited in their normal form. First among these we may note the materials found along the

162 BEACHES AND TID.\I. MARSHES.

straud which liave not been derived from the wearing of the hind or from the impcn-tation of pebbles or shells brought in by the scouring action of the waves from the neighboring shallows.

First among the list of casual contributions to the beaches we should perhaps reckon the debris from the arts of man. This consists not only of ordinary wrecks, which find their way to the beaches, but of a quantity of other materials derived tVom the arts. Noting first the wrecks, we observe that where a ship goes ashore on a bowldery beach, its framework, however strong, is likely in a few years to be beaten to pieces by the hard strokes which the stones deliver when set in motion by the waves. If it be a tim- ber vessel, the fragments are ground to fine bits, and float away. If the craft be of iron or steel, the oxidizing action of the sea water, together with the wave work, insures a slower j-et com- plete destruction. Rarely is any part of the wi-eck built into the submerged portion of the beach.

It is otherwise where a ship is wrecked upon a sandy strand. Because there are no stones to strike lieaAy blows in times of storm, the firmer parts of the vessel may endure in a little- Avorn state for many years. In some cases, hewn timbers ex- posed to the stroke of a powerful surf will keep their scpiared shape for a decade or more. If they are below the level of high tide, they are apt to receive some protection from the l)arna- cles, shellfish, and other organic forms which find a lodgment upon them. Moreover, the whirling currents formed when the waves break against the hulk ai-e likely to excavate the sand beneath the bottom, and thus allow the remains of the craft gradually to settle down into the loose material ; so that in the course of a few years the framework of a considerable ship may disappear from view. If the beach goes on widening (a pro- cess which is apt to take i)lace), the vessel may in time come to lie quite a distance inward from the margin of the water ; there it may lie hidden, unless some whii-ling action of the wind, such as makes and unmakes dunes, strii)S the covering away. A sec- tion across any one of the wide beaches of Europe, which has been receiving wi'eeks for two thousiiiid years or more, might well disclose a succession of castaway vessels dating from the beginning of the seafaring art to the present day, lying one beyond another to the seaward in the order of their antiquity.

Along almost all shores of the open sea, the debris of other human arts exceeds in (luantitv that which comes from wrecks

COMPOSITION OF SAND BEACHES. 1G3

oecurring on the shore. The range and variety of this del>ris which bears the impress of the hand of man are exceedingly gi-eat. On ahuost every sandy lieach in New Enghmd the trained observer can find in a few minutes' walk fragments of shaped wood which have evidently drifted from the tropics,' borne northwardly by the Gulf Stream, and driven away from its surface by the winds which blow shoi-eward over that cui-- rent. Along the coast of Fk)rida it is common to find logs of mahogany hewn into shape on the Imnks of rivers in South America and Central America. So consid(>rable is the amount of wood carried northward by the (xulf Stream, that the people of far-off Iceland obtain their supplies of such material from the drift which comes upon their shores. Thus iml:)edded in an extending sand beach we may find the more solid parts of trees which have journeyed from the Equator to the Arctic Circle.

Yet another curious element in the composition of the sand beaches is the volcanic pumice, which i>lentifully finds its way in ocean currents from one sea to another, and which naturally di'ifts to the shores. In almost aU volcanic eruptions of a high order of intensity, the (juantity of this lava, so filled with gas and steam vesicles that it will float, is very large.

When pumice comes to the sea, it is capable of floating for a very long time. Unless it becomes weighted down by the growth of animals and plants, the bits are apt to find their way to the shores. Inspection of the sand beaches along the Atlantic coast of the United States shows that this puraiceous matter is an im- portant element in the composition of these strands. It seems likely that any cubic yard of the sand from the shores which face the open sea will reveal recognizable fragments of this nature, though the greater part of the bits will be of small size.

Coming U])on peblily beaches, fragments of pumice, because of their frail natui'e, are (juickly ground to unrecognizalde pow- der. On sandy shores, although the material is broken up by the action of the waves, the process of conmiinution goes on more slowly. As might be expected, the amount of pumii-e which comes to the shores varies greatly on different parts of the coast. Thus along the shore of Florida, from Bay Biscayno north- ward to Ju])iter Inl(4, the writer has found fragments of pumice more plentiful than on any other portion of our shores.

Peculiar Features in Beach Structure. — Having gained a general idea of beach structure, the student should now notice

IG-t BEACHES AND TIDAL MARSHES.

certain peculiar features whicli may lie observed ou the surface or in the interior of these acciuuulations.

The most interesting marks which may be noted on the shore are those which are formed by the movements of the water as it is impelled by the waves. These are of a very varied nature. Selecting any pebbly beach where the stones are prevailingly of small enough size to be readily tossed about by the waves, the observer will note that at almost aU times, but especially after a heavy storm, the slope from the high-water line downward is scalloped in a ciu'ious manner. From the level beyond the waves, ridges tapering outwardly extend down the incline, it may be, for a distance of from ten to fifteen feet or more, and a height of from a few inches to two or three feet. Between these ridges, which taper toward their k)wer and outer parts, there are small wedge-shaped embay ments, which at the outer edge of the ridges may be from two or three feet to fifteen or twenty feet wide, tajieriug thence, like the section of a rather pointed cone which is obtuse at the apex, to the edge of high water. These scallops may, luider favorable conditions, be traced in orderly and uniform succession along miles of shore.

It seems to the wi-iter that these scallops are formed about as follows : In a time of storm the inner edge of the swash line formed by the body of water which sweeps up and down the beach has a very indented front, due to the fact that it is shaped by a criss- cross action of many different waves. As these tongues run up the beach and strike the pebbles, they push them back so as to make a slight indentation where each tongiie strikes. As the water goes back, it piUls out the fine material, but does not withdraw the pebbles. The next stroke of the splashing water then finds a small bay, the converging horns of which slightly heap uji the fluid, making the stroke a little harder in the cen- ter of the tongue, and excavating the bottom of the bay still further. As the reentrant gi'ows larger, and the tide rises higher, the water, as it runs up, forms a small wave, which breaks on the shore of the recess, and casts the pebbles more into the form of a ridge. This action, continuing for some hours before the tide turns, serves to shape the embaymeut.

It shoiild be carefully noted that, when the swaying waters rush up into the shore scallops, the converging walls of these indentations deepen the current, and add to the efficiency of its movements, — a ^Jrocess which is essentially like that which is

ELEVATED OE DEPRESSED BEACHES. 105

brought about wlieu an ordinary wave enters into a recess of the cliff, or the tidal undulation is crowded into an indentation such as th(3 Buy of Fundy.

Reference has been made to the fact that the water from tlie laud emerges through the upper part of the beach. If the quantity is large, it may happen that the fmtflow is sufBeient to keep the grains of the debris some distance from one another. In this case quicksands are formed, wliich may be inconvenient or even dangerous to the unwary explorer. Quicksands are of relatively rare occurrence along the seashores : they are more abundant on the beaches of rivers, where the conditions favor the escape of springs upward through the accumulations of sand.

Here and there, where waters from the lagoons behind the beaches have made fresh-cut channels, the observer may note the peculiar form exhibited by the beds or layers of which the beach is composed. He will see that in place of the orderly suc- cession of beds which he may have noticed in ordinary stratified rocks, which in almost all cases have been formed on st-a bot- toms away from the shores, the beach strata are considerably inclined, and that each layer or group of layers is apt to l)o inter- sected by other layers lying at different angles. Tliis tangled structure is recognized by geologists as a characteristic mark of beach accumulation. It somewhat resembles the layers foi'med in dunes and those built in deltas. It will be worth while for the student to work out these differences, if, as is often the case, the sand beaches which he is studying afford oj^por- tunity for such inquiries.

Elevated or Depressed Beaches. — We have now completed the outline description of the conditions which determine the formation of beaches. There remain, however, many minor yjoints of much interest, which should be set forth in order to complete the account of these interesting features. First of these we may note the elevated or depressed beaches formed along shore lines, which have, since their i)eriod of activity, been lifted above or lowered beneath the surface of the waters.

Along nearly all the coast lines which have been attentively examined by the students of coast phenomena, it has been ob- served, that, at various heights above the present sea level, there are more or less evident remains of ancient sea beaches. Thus, scarcely any portion of the Atlantic coast of the United States has failed to yield evidence of this nature. Geneivilly

lot) BEACHES AND TIDAL MARSHES.

speakiug, marks of this contact of the sea aud laud duviug foiiner adjustments of level are most conspicuous at heights of less than one hundred feet above the present shore; but in many cases they may be indistinctly observed at several times that elevation. It will be readily understood that the liigher a beach is in general, the longer the time dui-ing which it has been sub- ject to the agents of destruction — the rain, the friist and wind, as well as the cutting of the streams — which tend to destroy its original form. It is therefore rarely the case that we can definitely trace the position of shore lines which were formed during the earlier geological ages and afterward elevated into the air. In fact, all the important raised beaches which are well known are of geological age and date.

Although the course of the land movements is generallj' upward, it not infrequently happens that the downward settling or tilting of the laud carries the sea margin below its original l)Osition. Such accidents can rarely be traced, except by in- direct evidence. The slope of the beach, or even the character- istic ridge of a sand barrier, is likely to be obliterated by the dragging action of the waves. It is sure to be leveled over by deposits of detritus, so that its form cannot be traced by the sounding lead. It is only where steep sea cliffs have been lowered beneath the water that we can expect to find any evi- dence by soundings that a recently formed shore line has been depressed beneath the siu-face of the ocean. All along the At- lantic coast, from Newfoundland to Florida, there are abundant exidences afforded by submerged forests, which go to show that the shore line has recently been much farther out to sea than it is at present. Other proofs of the same general nature are afforded by the extent to which river valleys excavated by stream action have been invaded by marine waters. These con- siderations, though more evident to the trained geologist than to the beginner in the science, may be taken to prove a subsid- ence of the Atlantic coast line, or at least a relative gain in the height of the sea waters, which has brought the shore inland from a former station for a distance of some miles.

In considering the uprising and downsinking of beaches, it need not be supposed that gi'eat differences in the movement of large areas of the earth's surface are involved in these diverse residts. It seems likely, indeed we may say almost certain, that the interior parts of the continents are generally

EFFECT OF BEACHES IX THE FOKMATION OF H.USUOKS. KiT

moving upward, while tlie sea floors are geuerally rnoviug downward, in those great wrinkling processes of the earth's crust which developed the arches of the land and the Imsins of the sea. In this movement, which the reader may for conven- ience represent to himself by holding a pencil in the middle of its length and in a sloping position, it is evident that we may regard the section from the interior of the land out to the ])f)t- tom of the sea as a bar or lever, which has a fulcrum point rep- resented, in the case of the pencil, by the point at which it is held between the fingers. Now, if it happens, as it prol^ibly does in most cases, that the fulcrum point is near the shore, we easily perceive that the land may rise and the sea floor sink without necessarily de}iressing or elevating the l)each. If, on the other hand, the fulcrum point is to the landward of the shore, the motion will carry the beach below the plane of the sea; while, if the rotating point be under the sea, the beach will be gradually elevated. In this way we may account for the very numerous changes in the position of beaches without having to suppose that the land changes the general nature of its movement.

Effect of Beaches in the Formation of Hahboks. — This is a matter at once of scientific interest and of economic impor- tance. There are two ways in which the growth of a sand beach may lead to the formation of shelters for ships. AYliere a sand- barrier reef forms offshore, it often happens that one end of the strip does not lie against any promontory, but ends in the open water. Instances of this sort may be noted at many points along the Atlantic coast of the United (States. Although the sea be- hind such spits of sand is commonly not very deep, the shelter which they afford is often of much value tt) the smaller vessels, such as are engaged in the coasting ti-ade. ^Vliere such a sand beach is extended by the action of marine currents, especially where it projects into a bay, its extremity is apt to be turned in its growth by the action of other currents until it assumes the form of a hook, sui-li as may be noted near Proviucetown, Mass.; at Cape Pogue on Martha's Vineyard; and at many other points along the shores to the southward. Another group of sand-bar harljorages owes its oiigin to the inlets or breaches which are formed where the waters of a lagoon, overfilled by the rivers, break out into the sea. Good instances of this nature abound along the Atlantic coast south of Cape Hatteras. These passages

168 BEACHES AND TIDAL MARSHES.

from the open ocean to the sheltered expanses of the lagoons or bays are generally shallow. In almost all cases they are mnch obstructed by extensive sand bars both on the ontside and inside of the opening, — shallows formed by the tidal currents, which obtain considerable energy as they move in and out of the nar- row chaimel. As a class, sand-bar harbors are, because of their shallow nature, of less value than are those which are formed in other ways; but in many regions, as along the southern coast of the United States, they are about the only shelters for ships.

SuMM.uu'. — "We have now considered the most important phe- nomena of beaches, and the share which these structures have in preserving the land from the assaults of the sea. It would be pos- sil)le to extend indefinitely an account of the facts of the physical nati;re which these structures exhibit. Such details, however, would best be left to the unaided inquiry of the student who undertakes the study of particular parts of the shore. Such a person will do weU to extend his inquiries along two lines, — the one leading to an investigation concerning the effect of winds from different du*ections in altei'ing the details of sand beaches ; and the other, to the development of the various s^jecies of animals and plants along both the rocky and the sandj' shores. Inquiries of the kind above advised may, if properly dii-ected, prove of gi'eat service not only to the original observer, but to the science which he is pursuing. Well known as are the coast lines in a superficial way, no portion of them has yet been so studied as to complete om- knowledge concerning the featm'es which they exhibit.

It will be well for the reader to understand that the foregoing account of beach phenomena deals only with the simpler results of the complicated forces which take effect along the lines where the waters come in contact with the land. Many of the more important jiroblems which are presented in this most interesting field of inquiry are not touched upon in this brief essay. Some of them, indeed (as, for instance, the details of wave action), have necessarily been avoided, for the reason that their adecjuate dis- cussion demands a treatment by means of the higher mathemat- ics. It may, however, be hoped that enough lias been set forth, though in mere outline, to guide the student on the way to investi- gations which he may independently pursue.

THE NORTHERN APPALACHIANS.

By Bailey Willis.

ENUMERATION OF TOPOCiRAPHIC FEATUKES.

Usually a moiiutam range is iiiavk(Ml hy a central crest, but the Appalaoliian ranges are cbaracteri/,('(l by a central zone, the surface of which is lower than the ranges on either side. Tiiis zone is a very complex valley, or series of valleys, and is known l)y different names in different sections of its length of a thousand miles. In its entirety it will here be designated the "Greater Ai)palachian Valley," or the " Greater Valley," and its parts will be referred to by their local names. In eastern New Yoi'k the- Greater Valley lies between the Catskills and the Green Moun- tains of Vermont, and its southward extension is the Wallkill Valley and the Panlinskill in New Jersey. In Pennsylvania it includes the Lebanon, Lancaster, and Cumberland valleys; in Maryland, the Hagerstown Valley ; in Virginia, the Shenan- doah; and throughout Pennsylvania, Maryland, and Vii-ginia, the western portion is occupied by the Alleghany ridges. Still farther south it is the valley of East Tennessee, which, dividing at Lookout Mountain, extends into Alabama and Georgia.

Two principal ranges Ijound the Greater AiJpahu-hian ^'al- ley, — one on the southeast, the other on the northwest; the former being generally known as the Blue Kidge, the latter as the Alleghany Front. They extend in two nearly i>arallel lines about 75 miles apart.

The Blue Ridge is a mountain nnige of jirevailingly gentle slopes, rising to rounded spurs and knobs. It is everywhere soil-covered, and clothed in forests or cultivated fii^lds. It is nowhere naked or barren. In tliose sections where wealtli creates summer homes, driveways of easy gra(l(> swing around the broad mountain shoulders, which are dotteil with villas and sjiread with green lawns. Even in the more remote districts,

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fabius and eonifit'lds nestle among the mountain's arms, and cattle find pasturage on the summits. In New Jersey the Blue Ridge is represented by the highlands above Morristown; in Pennsylvania it is called South Mountain, and reaches an eleva- tion of 2,000 feet above the sea, or 1,000 to 1,500 feet above the adjaeent Cumbei'land Valley. Between the Susquehanna and Potomac the range lessens in l>ulk and height to narrow ridges but 1,300 feet above the sea. The Potomac, whose channel at TTarpers Ferry is at an elevation of .'>00 feet, is overlooked by the historic eminenciv of Maryland and Loudon heights, which are but 800 feet higher than the river. Southward through Virginia, however, the ridge becomes broader and higher: 30 miles from the Potomac the altitude is 2,000 feet; 17 miles farther is Mount Marshall, 3,150 feet; 11 miles beyond is Marys Rock, 3,000 feet ; and Stony Man and Hawks Bill, 4 miles and 7 miles V''si>i'<'tiv('ly from Marys Rock, and opposite Luray, are 4,031 and 4,0()() feet aliove the sea. These are the highest sum- mits of the Blue Ridge north of North Carolina, and it is 10 to 10 miles across at this point. In the section between the Poto- mac and Mount Marshall there are three deep gaps, — Snickers, Ashby, and Manassas gaps, — cut down to levels of about 1,000 feet. Manassas Gap, farthest from the Potomac, is about 50 feet deeper than the other two ; and waters of the Potomac, the Rappahannock, and the Shenandoah rise in a small plain east of the gap. hi the section south of Mount Marshall and extending 100 miles to the James there are numerous gajts at an altitude of about 2,300 feet.

The western wall of the Appalachian trough, the AUeghanj' Front, is characterized in its typical development by a bold southeastward-facing escarpment and a gentle northwe.<5tward slope. It is the edge of the Alleghany Plateau. Its northern end touclics tlie Hudson River, and is called the Catskill Moun- tains. Thence it stretcln^s southwestward with a general eleva- tion of 2,000 feet; l)Ut in northeastern l?ennsylvaiiia the Front is lost among the ridges which form the rim of the anthracite coal basins. Tlie plateau is characteristically developt'd, how- ever, west of "Wyoming and Nittany valleys, and the Alleghany Front is equally well marked. In this section it is climbed by the Pennsylvania Railroad in the Horseshoe Bend between Altoona (l,"lS() feet) and Oresson (2,020 feet). The Front crosses Maryland between ('umberland and Frostburg; Dans ^Mountain,

TOPOGRAPHIC FEATUUES. 173

2,100 feet abov'e the sea, being a eoiispiciious point. South of the Potomac, it rises in the Pinnacle to 3,007 feet, in Pigeon Roost to 3,400 feet, and in Roaring Plains to 4,400 feet. Little High Knolj, 20 miles from the Potomac, is a corner, 4,200 feet above the level of the sea, in tlie boundary between Virginia and West Vii-ginia. Thence southwestward the Alleghany Front declines in elevation, and becomes less sharply marked. The Chesapeake and Ohio Railroad pierces it in a tunnel 2,100 feet above the sea in passing from the head waters of the James River to the vallej* of the Greenbrier River. New River, flow- ing northwestward, enters the plateau in a canyon 1,500 feet deep, the general elevation of the crest being more than 3,000 feet. In the Big Black Mountains of Virginia and Kentucky the FrOnt again attains heights of 4,000 feet ; but the summit is lower in Tennessee, and at Cumberland Gap it is but 1,G00 feet.

Many streams cross the Alleghany Front. Rising in the plateau, they all, with the one conspicuous exception of New River, flow southeastwai'd, and emerge from deep canyons into minor valleys of the Great Valley. It will be seen later that in its apparently peculiar northwest course New River pursues the more natural direction of flow, and that the Delaware, Susque- hanna, Potomac, James, and Roanoke rivers reverse the <!Ourses they might, in the light of the ancient history of the province, be expected to take.

As compared with the Blue Ridge, the scenery of the Alle- ghany Front is rugged, yes, savage. The eastern face is steep, lofty, and often crowned with a precipice of sandstone. The canyons, a thousand feet deep or more from the plateau to the rivers, are narrow, and the profiles of the opposing walls are as bold as the eastern escarpment.

Between the opposite ranges of the Blue Ridge and Alle» ghany Front stretches the Greater Appalachian Valley. Its sur- face has a general slope, which is interrupted by depressions and heights. The depressions are channels cut by the streams in intaglio (that is, sunk below the general surface) 10 feet to 200 feet deep. The heights are long, narrow ridges, which remain in bas-relief (that is, stand out above the general surface) upon the plain, rising 000 to SOO feet above it. They are ranged in lines, frequently parallel among themselves and to the Blue Ridge or Alleghany Front. Through Pennsylvania they sweep in a majestic curve, which is followed by all the ridges from

174 THE JJOKTHEltX .U>PALACHUNS.

Kittatinny Mountain to the Alleghany Front, and which bends down into Virginia as far as New River.

A strip along the southeastern side of the Greater Valley is distinguished from the northwestern portion by the general al)- sence of ridges above the prevailing plain. The ridgeless strip is known as the Appalachian Valley, the Great Valley, and locally simply as the Valley. Its surface rises from a least elevation of 500 feet above the sea, in Pennsylvania, to its gi-eatest altitude, 1,700 feet, in southern Virginia. Thenc*; southward it gradually declines.

Northwest of the Valley, dividing the Greater Appalachian Valley, iiins a ridge called Kittatinny (or Blue) Mountain, north of the Susquehanna and between the Sustiuehanna and James rivers more commonly called North Mountain. In Virginia part of the range is named Little North Mountain, and a higher one immediately northwest is North Mountain. Although divided by many gaps as deep as the Valley level, and varying in height from 200 to 1,500 feet, this ridge is a practically continuous fea- ture throughout a distance of 400 miles. Its crest is often a rocky ledge less than 50 feet across, yet it maintains a imiform elevation over long stretches.

Northwest from Kittatinny Mountain the Greater Valley is di^^ded by the many parallel Alleghany ridges which succeed one another to the Front as wave lies beyond wave on the sea. They are generally narrow-crested, steep, and long. Hidden among them is Kishicoquillis Valley, a fertile plain 25 miles long and from 1 to 5 miles wide, completely encircled by moun- tain walls. Beyond them, in the sunset shadow of the Alle- ghany Front, are Wyoming and Nittany valleys. The former is slightly crescent-shaped, 55 miles long and (5 miles wide, and js smoothly floored by deep alluvial soil. It is the Northern Anthracite Basin. Nittany Valley presents a less even plain, the surface being deeply channeled by many streams ; but the fertile, rolling valley is charmingly diversified in its aspects, and contrasts beautifully with the escarpment of the Alleghany Plateau. Its length is 60 miles, but the southern arm, Mor- risons and Fi-iends coves, extends the feature 50 miles farther. The width varies from 2 to 10 miles, and there are several diver- gent coves.

In Virginia the Alleghany ridges are of a broader, less linear type. They are frequently oval, in horizontal and vertical sec-

TOPOGKAPHIC FEATURES. 175

tiou, both with comparatively smooth and gentle slopes. The valleys between tlie ranges contain still broader bnt lower I'idges, among which the head waters of the Potomac and James rivers flow in deep, narrow gorges. The soils are thin, and the dis- trict is less closely settled than the corresponding section of Pennsylvania.

Throughout Pennsylvania the Alleghany ridges are from 1,500 to 1,800 feet above the sea, but, like the level of the Valley, the Blue Ridge, aiid the Alleghany Front, they rise toward the south. In Virginia many of the ridges exceed 3,000 feet in altitude ; and Elliots Knob, 20 miles west of Staunton, has an elevation of 4,473 feet.

Ordinarily a great vallej^ is the home of a great river, which flows the length of the valley, gathering the waters from the en- vironing mountains. The Mississippi is an example; and in the Southern Appalachian ranges the Holston and Tennessee rivers above Chattanooga illustrate this relation of an extensive valley which holds a single river system. But in the Northern Appa- lachian ranges there are several river systems, and their main streams traverse the ranges in channels which are in a measure independent of the ridges. The Delaware, the Susquehanna, the Potomac, the James, and the Roanoke, all cross the heights. New River also cuts across, though in the opi)<)sitc direction. Even the tributai'ies are not confined liy the ridges. Following down some stream, we see the valley extending indefinitely, an easy path for the loitering waters. The mountains rise on either hand. Suddenly the river turns ofi' at right angles, and, dash- ing through a narrow gap in the forbidding ridge on one side or the other, emerges into another valley parallel to its former course. We shall see that the transverse rivers are older than the existing ranges, and that they developed their courses on a broad plain.

The rivers of the Northern App;ilachi;ins flow either to the Atlantic or to the Ohio River. The divide between these groups of streams is winding and" often inconspicuous, having no defi- nite rehition to the principal heights. The Delawar(\ Susque- hanna, and Potomac rise west of the Alleghany Fi'ont, which they cross, and, continuing eastward, traverse the Alleghany i-idges and the Blue Ridge to reach the Atlantic. From among the Alleghany ridges of Virginia, the James and Roanoke flow through the Blue Ridge eastward. New River, on the contrary,

176 THE XOKTHERX APP-VLACHIAXS.

has its source east of the Blue Ridge in North (^aroliua, and runs northwest across tlie Bhie Ridge, the Alleghany ridges, and the Alleghany Front, to the Ohio. Thus the main divide passes diagonally across the Appalachian ranges from a position north- west of the Alleghany Front in Pennsylvania to one east of the Blue Ridge in North Carolina. AVithiu the Greater Valley, between the Blue Ridge and the Alleghany Front, the divides between minor streams are intricate ; but, again, they are pecul- iar in being distinct from the valley ridges which they serve to connect, but do not follow.

DESCRIPTION OF THE TOPOGRAPHIC FEATfRES.

The marked characteristic of views in the Appalachian ranges is the level line in which the even ridge tops appear in silhouette against the sky. In landscapes, as in architecture, sky hues are tj'pical. The severe outline of a Greek temple is a form distinct from the gi-aceful spires of a Gothic cathedral. Not less widely do the even profiles of the Appalachians differ from the serrate sky lines of the Rocky Mountains.

From the deei:)ly cut channel of a stream in the broader stretches of the Appalachian Valley we may ascend to a hilltop of the general level. We climb a slope of soil, wooded or culti- vated, and advance upon the level summit of the knoll. It is not a commanding height, and yet in the absence of woods we may survey a broad landscape. There are many even-topped, rounded hills : they join one auothei', forming a gently rolling surface, in which the streams are more or less deeply sunk in intaglio. Were the trench-like valleys filled to the uniform ele- vation of the hilltops, the surface would be a plain.

Looking northwest or southeast, we see, limiting this cai'ved surface, a ridge which reaches far to the I'ight and left. Its crest meets the sky in an even line, which is broken here and there by gaps. Some gaps are slight V's, which scarcely inter- rupt the otherwise even line. Other gaps are cut down to water level, and are occupied by streams passing through the ridge.

This ■s'iew is across the trend of the ridges, across the gi-ain of the country. Turning to look in the direction of the trend, northeast or southwest, we may see rising from the plain a row of knobs, one behind another, each fai-ther one higher, to one which reaches the altitude of the level ridge tops. It is the end of a ridge which extends away for many miles.

TOPOGRAPHIC FEATURES. 177

Thus the relief of the Appahichiau laudscape has three classes of features: namely, the river ohauuels with their associated level bottoms; the upland or general level of the valley, which is more or less cut into I'ounded hills of nearly equal elevation ; and the ridges, which also in a general way rise to a uniform altitude. Let us consider these features more in detail.

It is the habit of rivers to do one of two things : they either dash swiftly down a rocky course, actively cutting the channel and carrying whatever sediment they receive; or they linger between alluvial banks, here and thci'e rippling over a gravel bar. Thus loitering, tlicy drop their burden of sand and mud, leaving it till a freshet gives them energy to lift and sweep it farther. Appalachian streains leap and loiter alternately. Usu- ally the quiet reaches extend where the waters wind about in the valleys trending northeast or southwest, and the cascades are found where they traverse a ridge descending to a parallel val- ley. But when a small stream joins one much larger, there is often a rapid or waterfall in the smaller of the two near its mouth.

Occasionally in the large rivers a swift current running in and out among rocky islets is margined by alluvial plains. Near Harrisburg, the Susquehanna, which is there broad and shallow, shows this association of a stream at work upon rock bottom, between banks of gravel and sand which it formerly deposited. The difference between the banks and the channel shows that the condition of the river has changed.

With a given current and volume, a river can transport a certain amount of gravel, sand, and mud. If it receives no more than it can carry, it cuts its bed; but if it is overloaded, it de- posits some of the sediment. In that case, if at some subsequent time the river should gain in volume or velocity, or receive less load from above, it would go to work to remove the beds of gravel or sand it had left behind.

The Susquehanna near Harrisburg Avas formerly overloaded, and spread alluvial formations broadly. Either because it flows more swiftly or is less loaded from its upper courses, it has now removed the sediments down to the rock. Other rivers also show this character.

The depth of the sunken channels cut by the streams in the general valley level varies with the size of the streams from r)0 to 600 feet. The great rivers have cut deepest, the smaller

178 THE NOKTHEltX APPALACHUNS.

streams less deeply, the brooks least; but all streams flow most of their courses in uarrow gorges with limited bottom lauds.

These channels are so intimately related to the streams, that there can be no doubt of the truth of one of two propositions: either the streams took up their present courses because they found them to be the lines of least altitude, or the streams flow- ing in these coiu'ses have cut out these lowest lines. In the guUey by the roadside or on the hillside, in a heavy rain, you may catch the rivulets at work. The shoAver over, you may study the forms they have carved. Down the guUej', dowu the brook, the creek, and the tril)utary to the gi-eat river, you can trace the features of the same class, though of constautly in- creasing magnitude, and, noting the burden of mud which the waters bear, you may realize that rivers do not tiud their valleys : they make them.

The general level, with which the dei>th of the river chan- nels has been compared, is not a uniform feature of the great valley between the Blue Ridge and the Alleghany Front. There are two classes of districts in which it is wanting. Near the larger streams it is usually worn away, or so divided into many low hills that it cannot be recognized. On the other hand, among the higher ridges, where they are closely ranged, the broad plain was not developed.

The plain is well preserved in the Lebanon, Lancaster, and Cumberland valleys of eastern Pennsylvania, and in their south- ern continuation, the Shenandoah of Virginia. It is also to be seen high above the present levels of the streams in the Nittauy Valley of central Pennsylvania, and in Kishicoquillis, which lies J, in the heart of the ranges. These valleys are all of limestone, with some areas of shale (or limy nuid rock) in the larger ones.

But the plain is not clearly evident in northern Pennsylvania in the anthracite basins, nor in the central part of the State along the Juniata, nor in West Virginia on the head waters of the Potomac and James rivers. In these districts, where hills rise above the rivers, yet do not attain the altitude of the high ridges, they are nevertheless of such height, and so bold in their outlines, that they do not immediately suggest the ancient plain out of which they have been carved.

The high ridges next demand description. We have seen that in the side view these ridges present a horizontal crest interrupted by gaps. With a nearly uniform elevation they ex-

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TOPOGKAPHIC FK4TURES. 179

tend for iiiauy miles, l)Ut at intervals of from cue to five miles tljey are notched to a depth of a hundred feet or more below the crest; and at longer intervals the notch is cut down to the base of the ridge, and is occupied by a stream. In the end view the section across one of these ridges resembles a right-angled tri- angle laid on its longest edge, — on the hypoteiuise. The apex of the right angle, then, represents the crest of the ridge; and the sides of the right angle are the slopes of the ridge. The cross section may, however, have various forms. One slope may be much steeper than the othei-. The steeper, being ]>er- haps precipitous near the sunnuit, departs from the straight lines of tlie triangle and descends in a curve, gi'adually becom- ing less steep ; the gentler slojie, approaching the horizontal, extends uniformly to some distance. This foi-ms the unsym- metrical ridge, of which the Alleghany Front, with its bold east- ern face and gentle westward slope, is the extreme type. In other cases the two opposed slopes are more nearly equal, and the cross section of the ridge may apjjroaeh symmetry or be quite symmetrical. In the symmetrical ridge both slopes are steep, l)eing nearly foity-ftve degnn-s lu'ar the sunnuit.

These sharji-crested ridges, called iiiohocUiki} ridi/cs, run in long Unes, straight or curving, often for many scores of miles. They may simply die out, but freqiieutly they pursue a shai-ply zigzag course. Then the ridge rises to a ciilminating point, higher than the extended crest; and from this point another ridge, which is really but a continuation of the first, returns at an acute angle with the former's course. The ridge and its opposite section, or continuation, are related in position as are the sides of a canoe, and the high peak occupies the i)Osition of the elevated prow. After a course of a few miles, tlie second section turns again, but less sharply and without a liighcr peak, into a third section, which extends parallel with the first section. At the end of the third section, where it passes into a fourth, there is again a higher peak, — a canoe prow, — and the angle of the zigzag is sharp. Valleys which lie between the first and second sections, or between the third and fourth, leading up to and ending in tlie pi'ow of the canoe, are called (■a)ioc rallcifn. Tlie intermediate valleys, lying in tlH> position lietween the sec- ond and third sections, have no familiar name; but they are aii- ticl'mal rrt//r//.s, ])vesently to l>e exidained, while the canoe valleys are more accurately described by the term si/ncliiidl rallnis.

180

THE NORTHERN APPALACHIANS.

Occasionally the canoe valley is simple, and closed at both ends, while tho drainajre escapes through one or more gaps in the side. Sometimes such a canoe occurs as a long, narrow, and shallow hollow in the crest of a mountain many hundred feet above the general valley level. The feature is then called a si/ticlitHiI mountain.

The "Wyoming Valley is an example, on a large scale, of a simple canoe valley. The anthracite basins are complex canoe valleys, and the zigzag ridges by which they are shut in are beautiful examples of their kind (p. 183).

These forms are the prevailing ones in Pennsylvania and Virginia. In both these States and in West Virginia there is also another type of ridge, which is oval in cross section and in longitudinal section. An example of this type may be found in Great North Mountain, which rises from the Valley northwest of Winchester, and extends 30 miles southwestward, declining to the North Fork of the Shenandojih River. Rock Enon and Capon Springs lie on its northwestern flank. This moxantain reaches an altitude of 2,700 feet in its nortlieni section, 1,700 feet above the general level of the Valley. In tlie same locality it is 3 miles wide at the base, and bears a broad, rounded summit. When seen in a view in which it presents its northern end, it re- sembles an arch. When viewed in a northwesterly direction, its

Syiii'liim! Fold, with Central Cauoe-sliaped Anticlinal Fold, with lliiiii-eiftar-shaped Valley. Mountain.

profile is hemi-cigar sliape. Tlie mountain is indeed an arch of sandstone, an anticline which has to some extent been denuded of the strata that formerly covered it.

In the central section of the mountain, which is crossed by the road from Middletown to Capon Springs, the sandstone auti-

TOPOaUAPHIt! FEATURES. 181

('line is itself cut through, and the t-rags that overhang the road on both flanks of the mountain are only the piers on which rested the arch. It spanned the valley of Paddys Run, that now lies in the back of tlic mountain.

Mountains of this oval type, anticlinal mountains, are some- times isolated from all other elevations by surrounding valleys. In other instances they lie en echelon, connected by a transverse divide much lower than their summits; or, again, two of them may coalesce at one end, forming a higher, broader summit than either possessed alone.

The canoe valley or synclinal valley may, as has already Ijeen stated, form the summit of a long, narrow mountain, whicli is then called a synclinal mountain. The arch mountain or anti- clinal mountain may, conversely, not only include a small anti- clinal valley in its crest, as Paddys Run Valley lies in Great North Mountain, l)ut the height of the mountain may be replaced by the hollow of the anticlinal valley. This occurs through the gradual expansion of the valh^y from the crest of the arch toward the sides and toward the ends, so that th(* lowest pai'ts of tlie long, narrow dome alone reinain. These then stand as mountain walls inclosing the valley, from which there may be but one gate- way leading out.

Such an anticlinal valley is Kishicoquillis, in Mifflin Coimty, Pennsylvania. Stone Mountain on the northwest, and Jacks Mountain on the southeast, completely isolate it, except for Logans Gap in Jacks Mountain, near Lewiston, — a pi(!turesque gorge through which Kishicoquillis Creek dashes. Passing through this ravine into the valley, the observer finds all the characteristics of the Great Valley reproduced. The stream flows in a channel wliich is cut deeply into the general siirface. Ascending to what appears from below to be a hilltop, it is found to be only the general level of the valley floor, which rep- resents a former plain. The eucomi)assing ridges are level- crested. Toward the southwest they converge to tlie apex of an acute angle. Across the nortlieastern end of the valley they are connected by the zigzag summits of Bi;ffalo Mountain, which re- semble the environing ridges of the antliracite basins.

The anthracite basins arc canoe valleys, but they lie high up above the channel of the Susquelianna, which receives the creeks that drain them. Tliey are therefore canoe-rallei/ mountains or synclinal mountains. Their topogra[)hic character is apparent in

1S2 THE NORTHERN APPALACHIANS.

thf aocoinpauj'iug reliof map of part of eastern Peimsylvauia. Keferriiig to the oxtrciiie northeast corner, we see Nescopeek Mountain extending southwest to Catawissa Mountain. Their junction is the western prow of a canoe valley which a few miles east contains the Northern Middle Anthracite Basins.

Cata^Wssa Mountain jiasses in a gentle arch into Little Moun- tain, which forms with Line Mountain a second canoe; that is to say, the bed of hard sandstone forming Little Mountain and Line Mountain is continuous, like the l)ottom of a canoe, beneath the space between them. Within this trough lies a second, which is narrower and shallower, being represented by Big and Mahanoy mountains; and within lie the coal beds of the Shamo- kin Anthracite Basin.

]\Iahantango and Berry mountains, Peters and Second moun- tains, form tlie outer rims of two convergent canoes. Coal and Lick mouutiiins, Stony and Sharp mountains, are paired as the inner trouglis, within which lie the coal-bearing measures. East- wai-d from Tremont these two basins become one, which extends beyond Pottsville to Mauch Chunk.

The preservation of the stores of coal contained within these basins is due to their environing ridges. The soft strata of the coal measures had been worn down to the level of the Lebanon Valley, and a very large proportion of the coal had been swept away to the sea ; but these walls of hard sandstone withstood the effect of erosion, and maintained the coal-bearing mountains.

The simple monoclinal ridge which has been def^icribed is the typical but not the more common form of the Appalachian ranges. They become complex by association of parallel ridges. Thus on the inner slopes of Jacks and Stone mountains, about Kishicoquillis Valley, there is a very marked bench or terrace, which api^ears as a broad step in the mountain slope. In other localities, wlien the outer edge of such a terrace is higher than its surface neai'ei- the mountain, there are narrow ravines sepa- rating tlie tci'riice edge as a low ridge more or less distinct from tlie mountain itself. The rivulets which gather in these ravines occur oppos(Ml in pairs, like opposite loaves o)i a stem, and their united waters flow at right angles to the trend of the main ridge through gorges in the lower ridge. Elsewhere, again, although ci;t through by many streams rising on the main divide, the sub- ordinate ridge may stand at a level equal with the continuous crest, and it then appears as a distinct monoclinal ridge. On the

if Map of Wosteiu Portion of tlip Antliiacitc Basins, IViiiisylvania. showing Canoe Valleys and Mountains and

the Course of the Susijuchanua across them, 18a

I

184 THE NOKTHEUN APPALACHIANS.

south side of the authracite basins ther«> are three such crests, which are nearly parallel, and are called First, .Second, and Third mountains; and there is ;dso Fourth Mountain, locally so called, hut it is in fact tlie continuation of Third Mountain on the north- ern side of a canoe valley.

In order that we may understand why these I'idires exist, why they vary in form, and why they jjursue such curious zigzag courses, we must observe the rocks of which they are composed. In the crests of nearly all Appalachian ridges occur quartz rocks of one variety or another. The rock may be a conglomerate of white pebbles, or a sandstone of coarse or fine grains, or a mass- ive rock called quartzite, breaking into sharp fragments; but quartz is the predominating mineral. Of all common minerals, quartz is the hardest and least sohible : therefore the quartz rocks longest resist the action of the atmosphere in wearing and dissolving them. Lime, on the other hand, is dissolved with rela- tive rapidity: therefore lime rocks, such as marble, limestone, and limy mud rocks, decay quickly in a moist climate like that of the Appalachians; the lime being leached out, and red clay remaining.

These two classes of rocks, quartz rocks and lime rocks, form the Appalachian region between the Blue Ridge and the Alle- ghany Front. There are many varieties, differing in composition, texture, and color ; but they all fall into the two great classes of the quartz rocks and the lime rocks, — the relatively insoluble and the more soluble. The soluble lime rocks occur in the val- leys and lower slopes of the ridges; the insoluble quartz rocks form the ridge crests.

The quartz rocks extend as beds of conglomerate, sandstone, or quartzite between the much thicker beds of lime rocks. These beds vary in thickness from a few inches to hundreds of feet, l)ut a single stratum of solid quartz rock more than iJOO feet thick is unusual. They extend downward from the surface at differ- ent inclinations in ditt'erent districts. In the Alleghany Front they lie almost flat. Their edges make the eastern slope of the mountain, and the uppermost one forms the surface of the plateau descending gently westward. On the other hand, in Kittatinny Mountain, near Harrisburg, the beds stand vertical.

The form of the ei'oss section of any ridge depends upon the inclination of the beds of which it is composed. Where the strata are gently inclined, the height approaches more or less

INDEPENDENCE OK S'lKEAMS AND VALLEYS. 1H5

nearly to the ehavaeter of a table inouiitaiu. In the steeper slope the edges of the beds are exposed. As the soft beds wear away, the liarder beds, behig uiiderniiued, break oft" in Ijloeks, and a liold front remains. Where the base material aeeunmlates, the roek face is masked, and cliffs are visil)le only towai-<l tlie sum- niit. Where the strata, on the other liand, are st(>ep]y inclined, tlie edge of the hardest bed makes the crest of the mountain, and more or less symmetrical slopes are woi-n from the adjacent beds.

INDEPENDENCE OF GREAT STREAMS AND GREAT VALLEYS.

Two rivers, rising in the Alleghany Plateau far west of the Alleghany Front, and joining in the heart of the valley ridges of Pennsylvania, form the 8ns(iu('lKuina. Their courses to their junction lie across many mountains; and the lower course con- tinues in the same manner across mountains, even though an easier route over j^lains was near at hand. This is well illus- trated in the channel of the Susquehanna a))Ove Hai-risl)urg, as shown in the map, pp. 170, 171.

The head waters of the Potomac li(^ in the plateau west of the Alleghany Front. Large tributaries running northeastward in the valley join it; and the principal one of these, the Slicn- andoali, is the largest river nortii of Tennessee flowing in the direction of the length of the A]>i>ala('hian Valley. But all tliese waters assume in the Potomac a soutlieasterly cliannel, wliii'h is cut across the hard beds of the valley ridges.

New River, which gathers its waters in North Carolina, does not follow the line of easy descent northeastward along the Great Valley to the Potomac or Susquehanna. It chooses instead a difficult way to the Ohio River across the Greater Valley and tlie Plateau.

These are examples of the; general fact that the streams of the Appalachian ranges are not controlled liy the mountains. The ridges i)ursue their courses, and the streams passing across the ridges pursue independent courses. The discordance is one of the most marked features of the topography, and it gives rise to many picturesqiie water gaps. As we shall see farther on, it is due to the fact that the transverse river channels are older than the valley ridges.

Within the Valley the brooks and creeks have arranged

18G

THE NOKTHERN APPALACHUNS.

themselves usually in systems of pairs. Flowing southwest, a Itrook meets its fellow running northeast, and together they turn

In the valley be-

southeast or northwest to traverse a riilgt

Types of Drainage resulting from Ailjustment to Beds of Hard and Soft Rouk.

In tlio northwest comer of tbc map tUe streams flow diversely over rocks which lie in horizontal bede. On the head waters of BUiestone River and Wolf Creeli the branches arc adjnsted to tilted hard and soft beds, fomiinp an example of " trelliscd " dniinase. lietwccu WoK and Hunting Camp creeks is an anticlinal arch. liiu'ke Garden, and the systems ot streams de- tine its position. Walker ("r<'ek and its branches also flow across tilted beds, but. as ihoy are more homogeneous than tlinsc ali>ii!.- the heads of Wolf Creek, the streams are less system- atically adUnsted.

HOW SCULPTURED. 187

yoiid the ridf^e they ave joiued l)y a pair siiiiilav to their own coui'ses before their union. Beyond a second ridge or a third, the growing creek may for a time flow northeast or southwest, but it will presently pass oiit by another water gap. Ultimately it falls into one of the great transverse rivers. This arrange- ment of parallel brooks, which swell the volume of a creek gen- erally flowing at right angles to their courses, resembles a vine from whose central stem branches are trained on a trellis. It is sometimes called the trdlis or (jrapcvine sij><tc'm.

Although most conspicuously developed in the Appalachians, this ti'ellis system of drainage is common in regions wdiere lieds of hard rock lie steeply inclined to the general surface. The parallel branches of the system are controlled by the parallel ridges between each two pairs. Thus it ap})eai-s that the liai-d rocks have to this extent influenced the arrangement of the streams.

HOW THE APPALACHIAN UPLIFT HAS BEEN SCULPTURED.

We have observed that the rivers flow in channels, which, like the gullies they resemble, have been cut by swift-rimning waters. We have noticed also that waters running less swiftly deposit mud, building flood plains or bottom lands. These two processes are as old as rivers and the force of gravity. In the course of ages they will remove mountains and spread plains. Let us ti'ace their work.

Streams which carry sediment cut like a saw. Like a circu- lar saw, they file continuously into the mass opposed to them. This is the mass of land above sea level, and they saw their chan- nels from their mouths backward into it. Thus every stream tends to cut its channel throughout its entire course down to the level of its mouth. But in this tendency it is checked when its fall becomes so gentle that it deposits sediment. Then it can no longer cut downwai'd, but it begins to carve sidewis(>.

By depositing sand or mud, a stream builds bars, from which it swings off against its bank. Undermining this, it is deflected toward the other bank, which it may strike and undercut in turn. Thus, when a river has filed its channel downward to a gentle sloi)e on which it deposits sediment, it then begins to wind sidewise, and with ever-increasing crookedness widens its valley. The rock and soil which it cuts away are swept on in

188 THE NORTHERN APPALACHIANS.

flood tide, aud are left by the subsiding waters, t'ormiug a flood plain. The Mississippi is thus at work.

Vallej's are widened by otlier processes wliich aid the streams. By heat aud cold, moisture aud frost, vegetation and solutiou, rocks are shattered and they decay. The talus and soil remain- ing sink down to a slope more gentle than that of canyon walls such as streams cut in hard rocks. The loosened material creejis down the hillside. Gullies grow backward into it, and develop many arras, through which the gathered waters of a storm sweep the soil to the lowlands. Every space betweeu the streams is attacked sooner or later, and the higher parts of the surface are graded down. The tendency is in time to I'eduee the land to a gently sloping plain, which extends from the sea to the head waters of the rivers. Such a plain is called a base-level.

The development of a base-level over a broad area I'equires a long time, and does not progress equally. There are many con- ditions that affect the rate at which the surface wastes, but that wliich most concerns us here is the relative softness or hardness of the rocks. In the moist Appalachian climate, other things being equal, a soft or soluble rock, like calcareous shale or lime- stone, wastes away much faster than harder or insoluble quartz rock, and therefore beds of the harder rock may long remain in relief above a base-level extended over the areas of softer rock.

Let us again look over the Appalachian landscape. It has certainlj' been sculptured by flowing water, to which the deep channels of the streams are due. Could some Titan fiU these channels level with the hilltops of the Greater Valley, he would restore a plain which would extend over the area of soft rocks between the ridges of hard rocks. This is the character of a base-level, aud we cannot doubt that such a jilain was developed by the sti-eams before they began to cut their present cliannels. Let us call this plain, which is well preserved in the Shenandoah Valley, the Shenandoah base-level.

Above this base-lev(4 the valley ridges rise 200 to 1,800 feet. Neighboring ridges are usually of nearly the same height, and their crests are often level lines, but slightly broken. Such lines are elements of a plain, and, with our eyes opened l)y sugges- tion, we may see that they do represent one. But it is only through the extensive landscape studies of Professor Davis and of Messrs. Hayes and Campbell that we are assured that the ridge tops were once even witli the surface of a base-level which

HOW SCULPTURED. 189

was much older than the Shenandoah Plain. Let us call this older plain the Kittatinuy base-level, because it is well preserved in the even crest of the long mountain of that name.

To restore the Kittatinny Plain ^ve must fill in with many cubic miles of rock all the Greater Valley between the Blue Ridge and the Alleghany Front, at least level with the ridge crests. This done, however, we should have a broad, dome- shaped elevation 4,000 feet above the sea in southwest Virginia, and sloping gently to the Atlantic and the Mississippi.

Geologists date this Kittatinny Plain as of the so-called Civ- taceous period of the earth's history. If we should compare all the ages since the beginning of rocks and oceans on the earth with all the years since luiman existence began, the Cretaceous period would correspond, perhaps, with the Roman occupation of Britain. Thus vaguely we may indicate that the Cretaceous belongs to the later periods of the earth's development. But the tiine which has since elapsed has been sufficient for the growth of the Appalachian ui)lift, and the erosion of its valleys and ranges. From what we have seen in the landscape, we may reconstruct an outline of this growth.

A base-level is the lowest slope to which rivers can reduce a laud area. With one margin it touches the sea, from which it rises imperceptibly. Unless it be very old and very completely planed, hills may survive at some distance inland, or over areas of the hardest rocks. Such a surface, which is almost, but not quite, a base-level, is called a peneplain. On such a surface the rivers meander in wide oxbows throughout their ^■allevs. There are no marked divides. Under these conditions, the i-hanni'ls of rivers are unstable features, as is that of the Mississippi or the Missouri; and, the fall of a river or system of rivers being very slight, a moderatt^ tilting of the land surface may suffice to change the courses of streams very greatly, or even cause them to flow in a reversed direction. The Kittatinny peneplain was very extensive, and almost complett^ly planed. The only heights in the Appalachian region wei'c hills which are now the jiioun- tain summits of western North Carolina, i)ut wei-e then at a lower altitude. The land was flat, featureless, and vei-y sliglitly elevated above the sea. The courses of the streams had been adjusted during the long period of erosion ; and the five rivers flowing eastwai'd had assunied that course in consequence of a tilting of the land toward the Atlantic, which caused them to

190 THE NOETHEKN .\PPALACHL\XS.

reverse their courses, which were formerly northwestward. New River did not share in this reversal, and remains to record the original slope from an eastern continent toward an interior sea. From this condition began the growth of the i:)resent Ap- palachian Mountains.

Along a zone corresponding with the present Great Valley the earth's sui-face rose unequally and very slowly to a maxi- mum height of about 1,400 feet in central Virginia. The eleva- tion grew very gradually, sloping to east and west, and to the Gulf of 8t. Lawrence on the north, as well as to the Gulf of Mexico on the south. Upon the surface of this broad dome the Susquehanna, Potomac, James, Roanoke, and New rivers mean- dered in i-ourses closely coincident with those they now possess. They had assumed these courses on the Kittatiuny base-level, where the beds of hard and soft rock of the Appalachian ranges were Imried beneath the alluvium of their flood jilains. As the base-level swelled upward, the rivers descended to the sea with swifter flow. They resumed the work of cutting their channels vertically, as they had done before the Kittatinuy Plain was base-leveled, and, removing the mantle of a]lu\-ium, they discov- ei-ed the solid rock ribbed with beds of sandstone and quartzite. Their com*ses lay across these beds ; and, although lines of easier channel cutting lay along the outcrops of soft beds, the gi-eat rivers could only persist in their channels, which they corraded as rapidly as the hard beds rose athwart their coui'se. The water gaps by which these rivers pass across the ranges, such as that at Harpers Ferry, and those on the Susquehanna above Harrisburg, and that on the Delaware near Strou(lsl)urg, are the result of the rivers' sawing.

On the Kittatinuy Plain many smaller streams flowed across the ranges ; and they also, persisting in their courses during the upheaval, cut water gaps in the hard beds. But they could not deepen the gaps as rapidly as did the great rivers, and the work of the smaller streams is now represented by the notches in the ridges high above the Shenandoah Plain. No streams now flow through these little V's : they are nind gaps from which a ri^^l- let descends on each side of the ridge. Further explanation is necessary Ijefore we can understand how this change has come about, but a discussion of a single instance will make it clear.

The Potomac traverses the Blue Ridge at Harpers Ferry. South of this water gap are several wind gaps, such as Snick-

HOW SCULPTURED.

191

ers Gap, which mark the chauuels of aucient streams, now diverted. The Shenandoah Eiver enters the Potomac above the water gap at Harpers Ferry, flowing northward along the

	^\
	•> J)
	^ //
	". //
	''^	, ,.'
THE	o.J^	•.^A4/en
KITTATI HNY	y^
PLAIN
	f( ■■ ■■ O
S^	y ./ Q
	/ ■ . ■ '^
Jf	/ *^
" — ^^
.#^	A3i	{'ri'^fv
^;^' ^''	^	'—^
/y
\f

Arrangement of Streams nn the Kittatinny Plain.

.Uljunted Streamn on the ShenantloaK ['lain.

Methods and Kesults of Kivor Piracy.

western base of the Bhie Ridge. The streams which passed through Snickers Gap and the other wind gaps ran above the present course of the Sheiiaudoiih, ci'ossing it al)ont at right angles. The two drainage systems could not exist at one time: therefore it is evident that the older one has been replaced by .the younger river, .the Sheuandoali. This diversion took place by the gradual growth of the Shenaudoali from its mouth south- ward. The Potomac, the large stream, cut its water gap faster than Snickers Gap was cut. The Young Shenandoah of the Kittatinny Plain, a small ti-ibutary of the Potomac where tlie mouth of the present Shenandoah is, acquii-ed considerable fall as the Potomac deepened its gorge, and sawed its channel down rapidly in the limestone, which offered no great resistance. But the stream in Snickers Gap, with perhaps less fall and not nuu-h greater volume than the Shenandoah, had to saw nuich harder rock in crossing the Blue Ridge. Its channel remained high, therefore, as compared Avith that of the Shenandoah. The latter,

19'_* THE NOKTHEKN APPALACHIANS.

exteudiug its head waters backward as a tree puts out new twigs, eventually tapped the channel of the other stream above Snick- ers Gap. The waters above the jwint of attack joined the Shen- andoah ; the section between the point of attack and Snickers Gap was reversed as the Shenandoah rapidly deepened the chan- nel of its new conqiTcst ; and the lower portion of the stream, now called Bejncrdam Creek, having lost its original head waters, took its rise at Snickers Gap. Thus the ancient stream which once flowed through the gap was divided into three sec- tions,— the diverted, the inverted, and the beheaded, — while the Shenandoah, the diverter, was strengthened.

By successive captures of tliis kind the piratical diverter has grown, until it is now the largest of the rivers within the Val- ley; and its head waters approach the channel of the James, wliich it may in time add to its conquests.

This process of capture of a small sti'eam by a larger one, or of a stream cutting hard rock by one making a deeper channel in soft I'ock, or of a sluggish stream by one having a rapid fall, takes on many aspects. It is a phase of that adjustment by which rivers tend to take the easiest route to the sea.

Furthermore, in consequence of this adjustment, streams are diverted frona areas of hard rock to areas of soft rock, and the hard rocks remain as divides. Thus in the case of the Shenan- doah all of tlu' formerly indei)endent streams which crossed the Blue Ridge are now concentrated in the channel of that one river. The coml)ined waters are working rapidly to reduce the surface of the Shenandoah Plain, while the Blue Ridge remains subject only to the attacks of rain and tiny rills. Adjustment of streams not only establishes divides on the hard rocks, but also diverts the waters that are cutting across tlunn.

The drainage system of the Kittatinny Plain was developed in the alluvium of the base-level. When it discovered the hard and soft rocks of the Ajipalachian zone, it was out of adjust- ment, and the streams competed for tlunr courses after the manner described. The more powerful or more advantageously situated rivers held their own, and conquered their neighbors. Thus there are in the ju-esent drainage system the older rivers which occupied their jiresent channels when carving the Kitta- tinny Plain, and the subsequent streams wliich developed as the upheaved plain was cut into.

"When the upheaval was in progress and while it was young.

HOW SCULPTUKED. lijij

the cavviug was intaglio, — canyons or deep channels like those of the present landscape were sunk toward sea-level ; but as the streams became adjusted among themselves and to the ranges of hard and soft rocks, and their fall lessened, they began to widen their valleys. In course of a long time they carved out the Greater Valley, leaving the ridges of hard rock in relief, to record in their level crests and wind gaps the extent of the Kit- tatinny Plain and the direction of its drainage.

The arching of the somewhat corrugated dome which bi'ought aljout the adjustment of the streams proljably went forwanl steadily, though gradually. It ceased, and for a relatively long period the Appalachian uplift remained about constant in ele- vation. The adjusted rivers in their lower courses constructed flood plains, which spread toward tlie head waters as the vall(>ys were ci;t more deeply. A base-level plain was extended througii- out the valley from the great rivers back to the slopes of the ridges. It is now rejn-esented in the general level which wa liave called the Shenandoah Plain.

The Shenandoah base-level is less extensive than the Kitta- tinny was. It is limited to areas of the soft rocks. With these it is coextensive, and the period of its development was so long that all the areas of soft rocks, even to the head waters, were planed; but it was cut so short that none of the ridges of liai'd rock were anywhere leveled.

The swelling of the Appalachian dome began again. It rose 200 feet in New Jersey, 600 feet in Pennsylvania, 1,700 feet in southern Virginia, and thence southward sloped to the CJuU" of Mexico. Its vertical arcs are from the Mississippi to the Atlantic, from Nova Scotia to the Gulf. The axes of gi'eatest uplift lie along the central valley; but their relations are not simple, and the study of their details involves problems of stream adjust- ment which are of deep interest.

In consequence of the renewed elevation, the streams were revived. Once more falling swiftly, they have sawed and are sawing their channels down, and are prejiaring for the develoj)- ment of a future base-level.

In the valleys ]K)werful rivers are planing soft rocks. Along the ridge crests weak rivulets attack, but do not much affect, the masses of hard quartzite : therefore the ridges are being left in even higher relief, — the Appalachian ranges are becoming more acute.

VM THE NOETHEKN APPALACHIAXS.

GENESIS OF THE APPALACHLVN T\TE OF MOfNTAINS.

Narrow valleys aud linear ridges, arranged iu more or less complex relations, are often described as being of the Appala- chian tj-pe ; not because such ranges are uncommon features of the earth's surface, but because nowhere else iu the world is this form of topography so characteristically aud extensively devel- oped. Nevertheless monoclinal ridges and streams adjusted to longitudinal and transverse valleys, associated with syuchnal aud anticlinal valleys or mountains, are found in all moimtain systems except those which are composed mainly of volcanic or massive igneous rocks. We may recall the fact that the Appa- lachians are formed of beds of rock, — of hard and soft beds occurring in alternation and inclined at angles varying from the horizontal to the vertical, — and we should not expect to find this type of topography developed in masses of homogeneous granite, such as that which constitutes Pikes Peak or the south- ern part of the Sierra Nevada.

Bedded rocks are produced by various agencies, — by succes- sive eruptions from volcanoes, by winds, by flood waters of rivers or from melting glaciers, and by deposits of sediments beneath lakes aud seas; but of the deposits thus formed only those which accumulate beneath somewhat extensive bodies of water are sufficiently regular in bedding to develop into ranges of the Appalachian type when upheaved; and of such marine formations, only those which are so bent, during u]>heaval, as to present their ujiturued edges to erosion, develop the Appalachian type of topography.

As illustrations of these facts we may refer to the foothills of the Rocky ^lountains, where the "hog-back ridges" are typical forms ; or in Eurojie to the Jura Mountains and other outlying ranges about the Alps, which present very striking examples of monoclinal, synclinal, and anticlinal features.

Beds of sediment which are spread beneath the sea consist of gravel, sand, and clay, together with lime, and many other sub- stances in smaller pi-oportions. All of these materials are brought to the sea by rivers flowing from more or less extensive land areas, or are gnawed from the shoi'es by waves and carried out to sea by the undertow. A bed of sediment is spread, it is Imried beneath another bed of similar or different .sediment, which in turn is itself buried: and the layers harden into rock,

GENESIS OF THE APPALACHIAN TYPE. 195

forming, of sancl, sandstone; of clayey mud, shale; and of limy ooze, limestone.

This process of deposition goes on for ages. The materials vary in character according to conditions both on the land and in the sea. The strata become perhaps several thousand feet thick. They sink somewhat into the earth's mass; so that the sea, though receiving great volumes of land waste, remains deep. But after ages of subsidence, forces within the earth, whose origin and character are unknown, reverse the move- ment, and raise the sea bottom to form dry land. The strata may be simply upheaved and tilted from their original horizon- tal position, or they may be compressed by a force of inconceiv- able power which gradually bends them into corrugations that consist of successive arches and troughs.

This upheaval is the birth of a range of the Appalachian type. In a short time, as the earth's ages are counted, streams cut canyons in the newly exposed surface; in the process of adjustment to hard and soft rocks, jjiratical brooks grow to the stature of rivers by the capture of less favored streams ; through the resistance of hard strata, ridges develop) and become prom- inent; but in time the surface is reduced to a peneplain, and the rivers, meandering broadly in their extensive flood plains, are liable to great changes of course in consequence of gentle tip- ping of the land. During a subsequent age the subterranean forces may again act to upheave the land ; the rivers are then revived, and begin anew the process of degradation, which ceases only when the monotonous base-level is extended over the land. The process includes the development and the wast- ing-away of a generation of ridges, and thus generation after generation may succeed one another as often as the earth's sur- face rises higher than the level of a peneplain.

Such has been the genesis and history of the Appalachian ranges.

During the Paleozoic era, an era long prior to the develop- ment of the Kittatinny Plain, a seashore extended where now the Blue Eidge rises. It was not the Atlantic coast of a smaller North America. It was the western coast of Appalachia, a continent which lay between an interior sea on the west and the Atlantic on the east. Beneath the interior sea were deposited sediments, which formed the beds of rock now found in the Appalachian ranges. In the movements of the earth's rocky

i;)l) THE NOKTHERN .\PP.\LACHIANS.

envelope the strata between the Blue Ridge and the Alleghany Front have been bent and upturned. Their edges are now ex- posed throughout the Greater Valley. But the zone in which the beds are thus steeply inclined extends from the Blue Ridge westward only so far as the Alleghany Front. In the Front itself and in the plateaus west of it the strata approach a hori- zontal position. The steep face of the Front, which is turned eastward, presents to view the edges of the fiat beds.

In enumerating tlie ]trincipul features of the Nortliern Appa- lachian ranges we distinguish three, — the Blue Ridge, the Greater Valley, and the Alleghany Front. We now see that these three divisions are genetically related, and owe their characters to geographic conditions that no longer exist. The Blue Ridge is part of the ancient continent of Appalachia, which, being composed of hard but generally homogeneous rocks, maintains a mountain range vrliose forms are rounded. The Greater Valley corresponds to a zone along the shore of the ancient sea, where the littoral formations consisted of alternat- ing beds of sandstone, shale, and limestone. These beds have been bent into arches and troughs, and in process of erosion their edges have developed as linear valleys and ridges. The Alleghany Front is simply the edge of the plateau, the edge of the region of nearly flat-bedded rocks which have been raised withoiit marked bending. The three constitute a group, in ■which the Bhie Ridge may be called a rontiiiciital range; the Greater Valley, a tiltriJ Utfnral zone ,• and the Alleghany Front, which confronts the old continent of Appalachia, an ii/land- facing escarpme)it.

These names imply a recognition of seas and shores that have vanished, and which were not fixed features even of the earlier geographic conditions. Shores are shifting lines, and migrate back and forth over land surfaces. But the three gi'eat topo- graphic divisions of the Appalachians may nevertheless be classified according to the conditions in which they originated. Thus considered, the Appalachian ranges are found to be a remarkably complete development of a type whose homologues are distributed in all continents.

INFLUENCE OF THE APPALACHIANS ON SETTLEJIENT.

The Appalachian ranges lie l)etween zones of plateaus. On the east and southeast are the Piedmont Plateaus, and on the

INFLUENCE ON SETTLEMENT. 197

west aud northwest are tlie Allegliauy Plateaus. Beyond these zones respectively lie the Atlantic Coastal Plains, aud the Prairie Plains, bordering the Mississippi Valley.

The plains were the homes of the most populous Indian tribes, and they were first settled by the invading Spanish, English, and French. The ranges of the mountains separated these peoples, and were a barrier to intercourse long after the several topogra})hic provinces had come under one national government, and their inhabitants had become one nation.

In this connection it is desirable to note certain characteris- tics of the Appalachians, bearing upon their effectiveness as a barrier. The ranges are marked by great length. They are continuous along hundreds of miles. Like a series of gigantic walls, they lie athwart the path of one Avho travels northwest- ward. They are pierced, it is true, by numei'ous passes, — the water gaps, — but the gajss through the successive ridges are not opposite one another, and they resemble rather breaches choked by debris than open gateways.

Before the days of railroads, or even of graded highways, the migrating Indian, or white man, made his way on foot, on horse- back, with pack horses, or by canoe. Uu the hunt and in war- fare he went unencumbered, and took little note of natural obstacles. To break through the underbrush, to climb among fallen trees and rocks, to ascend steep mountains, or to carry the light canoe around rapids, was the hunter's, the wai'rior's, accustomed task. But the family or the tribe, conveying house- hold goods, foimd thickets, Avindfalls, steeps, and cataracts most serious impediments to their progress, and they were controlled in the direction of their migivitions to a great extent by the ease or difficulty of journeying; and this was more especially the case when the best hunting gvoiinds or best farming land lay along the easiest route.

All the natural conditions which govern the welfare of a people inhal)iting a district depend more or less upon the tojiog- raphy. The flora, fauna, water sui)iily, h(>althfuluess, attrac- tiveness, and accessibility are conditioned by the nature of tlie soils, the evenness or i-uggedness of the surface, the elevation above sea, and the distribution of streams. The four great dis- tricts of the Appalachians — the Great Valley, the Blue Ridge, the Alleghany Ridges, and the Alleghany Plateaus — differ in all these respects.

198 THE NOETHEEN APPALACHLiNS.

The Great Valley is by uatuve adapted to be the home of a dense poinilatioii. It has harljored many peoples, who have warred for its possession. It was a natural route along which tril)es wandered from tiie pine or hardwood forests of the North to the cane-brakes of the South, or vice versa, and from which there was intermigration and commercial intercourse with the dwellers along the coast.

The study of the distril)ution of Indian languages, and of the ancient village sites, shows that probably two great waves of migration, and perhaps nioiv, passed through the Valley before Columbus landeil. The Algonfjuins, spreading from their homes about the Lakes and the St. Lawrence, pushed far to the south- ward, and, as fishermen and crop i-aisers, made their homes wherever fish were abundant or the soils fertile. Behind them and at a later period came the warlike tribes of the Iroquois, the most progressive of the Indians of eastern North America. The Iroquois of the Six Nations drove the Algonquius westward; and the Cherokees, also a branch of the Iroquois, occupied the Appalachians southward to Tennessee and Georgia. There they were overpowered bj^ the Watauga men under John Sevier, and driven to the Carolina mountains, where a remnant of the tribe still exists. The rising power of the Six Nations was likewise destroyed ; for their home in northern New York lay in the path of both Fi'ench and English, and they were drawn into the wars which foreigners waged for lauds that belonged to the Indian.

The immigration of the whites was directed by the natural highways, and limited by the mountain l)arriers. The seafar- ing Dutch and English found a congenial habitat aroiind the estuaries of the Coastal Plains. Slowly they worked their way westward. " Blue Mountain," signifying the asi^ect of the range from a distance, was the name they gave to the most eastern ridge; and it became so fixed during the decades which passed before they had a nearer acquaintance with the ni(iuntnins, that it survives to-day in two distinct ranges, — the Blue Ridge of Virginia, and the Blue or Kittatiuny Mountain of Pennsylvania.

In eastern Pennsylvania, however, the noi-thern end of the Great Valley is easily accessible; and settlement spread into it both north and south of the Susquehanna. In Virginia the low passes just south ot" the Potomac afforded easier routes across the ridge than the water gnp of the river itself, and they were occupied liy roads along which pioneers jiassed into the Valley.

INFLUENCE ON SETTLEMENT. 19U

There Wiuchester was lard out as a towu iu 1752. It does uot appear that the Virginians spread beyond the head waters of the Roanoke during the earlier immigration, the Tennessee region having been occupied from North Carolina by men who crossed the highlands of that State. The diversion of migration from the Great Valley eastward followed the natural features. On the head waters of the Roanoke two ridges rise to a height of more than 3,000 feet aljove the sea, between the Blue Ridge and North Mountain, and they appear so to close the Valley that the old maps show a range definitely limiting its southci-n extension. From this supposed mountain range, beyond which lay an unknown land, pioneers turned through the low passes of the Blue Ridge toward the Piedmont Plateaus of North Carolina.

In 1770 there was published in London the " American At- las," engraved by Jeffreys from maps and surveys dating from 1770 to 1775. These maps present an accurate picture of the extent of settlement, so far as it is indicated by the gi-owth of roads into the wilderness, and the existence not only of towns, but of houses which served as stopping places.

In New York the valleys of the Hudson and the Mohawk had been occupied, forming a belt more than 200 miles long from New York to the farthest outpost, which in 1775 was " Rynards, the uppermost settlement," 70 miles in a straight line beyond All>any. Eastward roads were continuous with those of New England, and towns were numerous ; but west of the Hudson and north or south of the Mohawk the zone of civilization was but 5 to 30 miles wide. The Adirondacks were dcscribeil as "a long chain of snowy mountains, . . . not only uninhabited, but unknown." That part of the Appalachian Valley from Ron- dout to Port Jervis on the Delaware, now the line of tht^ Delaware and Hudson Canal, was developed Ijy an " Indian Road opened in 1756," which extended to Easton and Reading. Thus the settlements were connected all along the northern and eastern sides of the Alleghany plateaus. The plateaus in southern New York and northern Pennsylvania were the " Endless JNIountains," and included the " Great Swamp." The broad ))lank on the map which these names cover west of the Delaware is expressive of a terra incoomta.

In Pennsylvania there were houses, mills, churches, and towns scattered throughout the region east of Kittatinny Moun- tain: that barrier limit(>d tlunr expansion. Lancaster was an

'JOO THE NOKTHEKX APP.VLACHIANS.

important ceuter, couuected by two roads with Philadelphia and Wilmington on the east, by three roads with points in the Lebanon Valley, and by two others with the West and South, as far as those parts of the country were then known. West of Kittatinny Mountain, however, was the labyrinth of the Alle- ghany ridges, through which few, save perhaps a Leatherstock- ing, could guide the injniigraut. Roads, which no doubt followed former Indian trails, are shown here and there on the map ; but it is evident, from the manner in which their courses appear to traverse the most diflficult ridges, that the map maker worked without accurate knowledge, and the beautiful series of ranges that is showu on pp. 170, 171, is delineated by him as a confusion of heights. The district of the anthracite basins is marked " St. Anthony's Wilderness," Imt the existence of coal is noted in several places.

Southward from Lancaster the main road ran through York, by Williams Ferry on the Potomac, to Winchester ; and Win- chester "was connected with North Carolina by a road extending along the western side of the Valley to the gap of the Roanoke in the Blue Ridge. Passing through that gap, it was continued to the Yadkin River in what is now Stokes County, North Caro- lina. This is marked " The Great Road from the Yadkin River through Virginia to Philadelphia, distant 435 miles." In all the fertile valley, from Winchester south, there was in 1775 biit one place worthy to be named on the map, " Staunton Courthouse."^ Probably along this road passed Daniel Boone when his father migrated from the frontier home near Reading to another on the Yadkin, whence Boone set out in 17G9 to explore the wilderness of the head waters of the Tennessee, and to penetrate along the route through Cumberland Gap to Kentucky. In thus marking out the " Wilderness Road," Boone overcame the mountain bar- rier which had elsewhere turned the tide of English immigration.

From the explorations of La Salle, a hundred years l)efore Boone's, France had laid claim to the valley of the Mississippi. No mountains barred the advance of the French voyageiirs, who sailed the Great Lakes, and made their way in canoes along the numerous rivers and lakes of the interior. Moreover, they adai)ted themselves readily to the Indian character and life, and thiis in the century of skirmishing which preceded the capture of Quebec they luul over the English the advantage of easy access to the interior and the aid of Indian allies.

INFLUENCE ON SETTLEMENT. 201

The fharacter of the French and ludiau War was iu large measure due to the separatiou of the aiitagouists by the t>road wilderness of the AUeghauy plateaus. Whatever blow Avas struck, whether it was an Indian raid upon the English, or Braddock's expedition against Fort Duquesne, was a l)low at arm's length. Even if successful, it could not be followed to decisive victory. In this harassing but inconclusive warfare the English were within, the French outside, the mountain wall. Like men be- sieged within a fort, the English were on tlie defensive, while the French could never muster force enough to break in, even through such natural In-eaches as the valley of Lake Cham])]ain and the Hudson.

Thus the Ajipalachian ranges, by confining early English immigration, gave those colonies sti'ength, and by excluding organized attacks protected them. But toward the close of the eighteenth century the dividing ranges sei^arating the English on the east from their countrymen on the west became a source of weakness.

In the years succeeding 1780 many thousand men, women, and children ci'ossed the Alleghanies to Kentucky. They went by three routes, two of which met at Fort Durpiesiie (now Pitts- Imrg), whence the journey was continued l)y l^oat down the ( )liio. The northern road from eastern Pennsylvania crossed the Sus- quehanna at Harris's Ferry (now Hnri-i8l)urg), passed along the Valley through Carlisle to 8hippens))urg, and thence woxuid through the Alleghany ridges past Bedford. Ascending fo the summit of the Alleghany Front, the road thence followed the highland between the waters of the Youghiogheny on the south and the Loyalhanna on the north. Thus it avoided the deep ravines which, clogged witji falkm timber, rocks, and dense growth of rhododendron, made the plateaus almost inqtassable. The second road ran from Fort Cumlierland (now Cnmberland, Maryland) across the Alleghany plateaus to Great Meadows, near the present site of Deer Park, IMaryland. Thence it turned north to the Youghiogheny, an<l followed that stream to the Monongaliela and to Pittsburg. This was the route cut out by Washington and Braddock in 1759. These were mountain roads of the poorest description. AVhere the natural surface was fairly hard and level, the track of one wagon was the guide of the next. In swamps corduroy made of logs loosely laid across the way formed an insecure bridge. In ravines the rocky bed of

202 THE NORTHERN APPALACHIANS.

the Stream furnished the roadway. On hillsides the narrow grade became deeply gullied. At seasons they became almost impassable, except to the ready frouticrsmau, who conld build around or bridge over deep gullies or treacherous mudholes. The third route was Boone's " Wilderness Trail " through Cum- berland Gap. Available only for pack trains, not for wagons, and, like tlie Ohio route, open to Indian attack, it was less used, though even along its rugged way many jiassed to join in build- ing up the new State in the West.

The men of Kentucky were strong, determined, and inde- pendent. They were separated from their kindred of the eastern seaboard by diversity of interests as well as by natural obstacles. Their prosperity depended on the commercial freedom of the Mississippi even more than that of the eastern communities depended on free commerce in the Atlantic ports. But the pol- iticians of the settled States were inclined to treat lightly the interests of the remote pioneer settlements, and especially to consider the navigation of the Mississippi as of little importance. Hence from ITS-t to 1788, during the negotiations with Spain in which she claimed the right to control the Mississip2>i, the allegiance of Kentucky to the United States was severely strained. Movements toward separation were considered. Had they been carried out, the division of the country would have been due in large measure to the broad wilderness which made the communities of the East strangers to those of the West. The Alleghany plateaus formed a natural barrier along which the States might have di^ndcd.

During the closing j-ears of the eighteenth and the earlier decades of the nineteenth century, projects of internal improve- ment related chiefly to the building of roads and canals to over- come or lead around the mountains.

Pittsl)urg remained the center of trade from the East to the SouthAvest, but as late as 1811 the principal route for traffic was through the Moliawk Valley by flatboats and wagons. Not until that year <lid Pennsylvania I'ouse to the importance of building a turnpike from Harrisburg to Pittsburg.

At the present time we traverse this distance in about nine hours. Kailroads liave penetrated the heart of the plateau region, and beyond the railroads tramways extend to the most remote recesses. The o])ject of their construction is to develop the natiiral resources of the forests and of the rockv strata.

NIAGARA FALLS AXD THEIR HISTORY.

Bv Ct. K. Gilbert.

The great catai-act i.s the embodiment of power. lu every second, uncea.'^ingly, seven thousand tons of water leap from a eliif one hundred and sixty feet higli, and the continu- ous lilow tliey strike makes the earth tremble.

It is a spectacle of great Ijeauty. Tlie clear, green, pouring stream, forced with growing speed against the air, parts into rhythmic jets which burst and spread till all the green is lost in a white cloud of spray, on which the rainbow floats. Its charms are the theme of many a gifted bard and artist, but the fascina- tion of its ever-varied yet continuous mo- tion, and the awe that waxes rather than wanes with familiarity, are not to be felt at second-hand ; and so the world, in long procession, goes to see. Among the multitude there are some whose appreciation of its power has a utilitarian phase, so that they think most of the mjiiad wheels of industi'y its energy may some day turn ; and there are a few who recog-

(Copyright, 1895, by American Book Company.)

Fig. 1. — AmLiieiiu I'all iiuiu bcluu.

L'04 XIAdAK.V FALLS AND THEU; IIISTOIIY.

iiize it as a gi-eat natural engiue, and in its activity and its sur- roundings see an impressive object lesson of geographic progi-ess. Its aesthetic and utilitaiian aspects need no exi)onnder, but its geographic signilioance is too little appreciated. This paper en- deavors to tell in simple language some of the lore of the pro- fessional geographer and geologist, in order that the layman may gain pleasure not only from the Iteauty and grandeur of the scene, but through understanding its meaning as a part in the great drama of nature.

Nature is full of change. The bud we saw yesterday is a flower to-day ; the leaf that was broad and green in summer, in autumn is shriveled and brown ; the biish we knew in childhood is now a broad, spi-eading tree. Such changes are easily seen, l)ec-ause they fall ^\ithin the span of a man's life, and so the pnucijile of perpetual progress in the organic world is familiar to all. Progress in the inorganic world is so slow that it is less easily seen, and there is a widespread impression that the hills are everlasting and unchanging. This impression is false. Not only hills, biit mountains, plains, and valleys, are perpetually acted on by heat and cold, sunshine and rain, wind and stream, and are gradually changed. Not only do they now undergo change, but by such agents each feature was originally foiined, and l>y such agents it will eventually l)e transfoi'med into a feature of dift'ereut type. Thus every element of the landscape has an origin and a history. To relate these is to explain it. This monograph may be regarded as an explanatory account of Niaa-ara Falls and the associated natural features.

THE DK.UXAGE SYSTEM.

The drainage system of the St. Lawrence is of exceptional character. In most regions the freshly fallen rain gathers into I'ills ; these, as they run, join one with another, making brooks ; brooks are united into rivers ; and rivers flow to the sea. In all its journey from the hillside to the sea, the water moves forward Avithout halt. This uninterrupted journey is rendered possible by a wonderful adjustment of slopes. The channel of the rill slopes toward the brook, the bed of the brook sloi)es toward the river, and the liver bed slopes "toward the sea. Impelled by gravity to flow downhill, the water moves continually forward from the beginning to the end of its journey. In the drainage

THE DE.UXAGE SYSTEM. 205

district of the St. Lawrence there is no such continuity of slope. The district is composed mainly of a gi'oup of great basin-like hollows, i)i each of Avhioh the suiface slopes toward some central point, and not toward the mouth of the river. Each basin is filled with water to the level of the lowest point of its rim, and each of the lakes thus formed is a storage reservoir i"ecei\ing a group of streams from the surrounding country, and pouring an even discharge over its rim to one of its neighbors. Lakes Superior and Michigan discharge to Lake Huron ; Huron over- flows to Erie; and Erie, having thus received all the outflow of the upper and greater lakes, sends its suri)lus through the Niag- ara to Ontario. The Niagara Eiver is thus, from one point of view, a sti'ait connecting two inland seas ; from another point of view, it is a part of the St. Lawi-enee River, — the part connect- ing two great esiaansions. Viewed_eithfir--way, it d^^pm-ts so jvidely from the ordinary oi' normal UiLer_tha,t4ts-nftffie i« almost mislea(lijUj8;^-

In a normal di'ainage system the slope is not everj-^vhere equally steep : it is gentler in the bed of the main stream than in the beds of tributaries, and it varies from point to point so that the ciirrent, esijecially at low water, shows an altei'uation of rapid and quiet reaches. The streams of the Laurentian system not only exhibit these alternations, but have many cataracts where the water cascades down a rocky stairway or leaps from the brink of a cliii".

A normal river receives most of its water directly from rain or melting snow, and varies with the season, swelling to a flood in time of storm or at the spring snow melting, and dwindling to relative insignificance in time of drought. The water of Niagara comes only remotely from st<)rm and thaw. The floods of the tributaries are stored by the lakes, to whose broad sur- faces they add but a thin layer. The volume of Niiagara dejiends onjy on the height of Lake Erie at Buffalqj_and Irom season to season this height varieslnit little. On rare occasions a westerly gale will crowd the lake water toward its eastern end, and the rivei- will grow large. On still rarer occasions a winter storm ^\^ll so }iile up or jam the lake ice at the entrance to the river as to make a dam, and for a day or two the river will lose most of its water.

A normal river, with its continuous current, rolls foi'ward the pebbles loosened by its tributaries till they reach its mouth.

20G

XIAG.UJA FALLS AXD THEFR HISTORY.

The rains that make its floods dislodge particles of soil, and wash them into the tributaries in such multitude that they discolor the water. The pebbles of its bed and the mud A\-ith which it is discolored are the river's load, which it transports from the face of the land to the bed of the sea. The tributaries of Niagara carry their loads only to the lakes, where the loads sink, and leave the water pure. Thus Niagara is ever clear. Sometimes, when storm waves lash the shores of Erie, a little sand is washed to the head of the river, and carried downstream ; sometimes a little mud is washed into the river by the small creeks that reach its lianks. Thus Niagara is not absolutely devoid of load, but its burden is so minute that it is hard to detect.

THE TWO PLAIN'S.

From Lake Erie to Lake Ontario the Niagara runs north- ward. The longer axes of the lakes trend nearly east and west,

and the lakes lap past each

L A E I j: n I £

Fig.

-Xiasara River ami Vicinity.

B J '^ Other for a distance of forty miles, including Ijetween their parallel shores a strii) of land al)out twenty-five miles wide. This strip, where the liver crosses it, consists of two plains, shai'iily separated by a cliff or est-arpment. The relations of the plains to the escai-pment and to the lakes are shown by the map (Fig. 2) and the bird's-eye A-iew (Fig. -4). The upper and broader plain has a gently undidating smface, which does not diflfer greatly in height from the surface of Lake Erie. Along the shore of that lake it rises in a low ridge, and there is also a gentle rise toward the escari>ment. Its middle part is di'ained by two .sluggish creeks, — the Tonawanda, flowing to the river from the east ; and the Chippewa, from the west. The lower and narrower plain follows the shore of Lake Ontario, and rises gently thence to the foot of the escaipment. Its ui)per part is of rolling contour, like the upper plain ; its lower is remarkably smooth and even, ha-\-ing once been the bed of a lake. The escarpment is a steep slope about two hundred feet high. Near the top it is generally a rocky

THE TWO PLAINS. 207

cliff, giving a sharply defined lioundary to the uiipev plain ; at the bottom it merges insensibly with the lower plain.

These surface features are definitely related not only to the peculiarities of the river, but to the rocky franiewoi-k of the country. The i'<icks are flat layers or strata I'esting one upon another, and of neai'ly uniform thickness for great distances. Nearly but not quite level, they slope gently toward the south; the descent, or dip, amounting on the average to thirty-five feet per mile. Their arrangement is illustrated by Fig. 3, which gives a north-and-south profile, with such a section of the fonnatious

IAK£: ESCARPMtNT

£f,ic Upper Plain | ^^^

l^er Plain Ontario

Fl(i. 3. — Profile and Section from Lakp to Lako. Vertical scale greater than horizontal. Base line ifprcsents sea level.

as might be seen if a very deep trench were dug from lake to lake. The heavy line at the left, and the Ijelt below divided into blocks, represent limestones, rocks notably hard and strong, while the intervening spaces are occuisied chiefly by shales, which are relatively soft and Avcak. Originally all the forma- tions extended farther to the north, Init they have been worn away ; and, since the soft rocks were removed more easily than the hard, the edges of the hard are left sonu'wliat prominent. This association of hard- rocks with uplands and cliffs is not rare, but is rather the rule in hilly and mountainous districts. In the last preceding monograph of this series, Mr. Willis describes the plateaus and ridges of the Appalachian district, showing how frost and .^torm slowly but i)ei-sistently ate out the soft rocks, and the rock waste was washed into streams, till valleys and lowland jilains were made.

The higher of the two limestones jn-esented in the diagram is called the Corniferous limestone. It makes a low ridge along the north shore of Lake Erie, and dips beneath the lake. The Salina shales occupy the middle part of the upper plain, and dip V)eneath the Cornifei'ous. The second limestone, called the Niagara limestone, constitutes the northern part of the uj^jjer plain, and the escarpment everywhere marks its northern limit. Its full thickness is about a hundred and forty feet, Init in some places it has been greatly reduced by the wasting of its upper surface. Below it is a gi-eat series of mud rocks or shales, a

208

XUGAKA FALLS AXD THEIK HISTOKY.

thousand feet thick, interrupted near the top 1 ly a few thin l)eds of Umestone and sandstone. These shales occupy the lowei- part of th(> escarpment and the whole of the lower plain. Their softness and the hardness of the Niagara limestone guided the erosive agents in making the escarpment and the lower plain.

Over all this rocky foundation lies a mantle of loose material. — clay, sand, gravel, and bowlders, — collectively called the driji. Its ordinary thickness is thirty or forty feet ; but there ai'e places, especially on top of the escarpment, where it is nearly absent, and elsewhere it fills hollows or is built into hills -with a thickness of several hundred feet. It was spread over the country after the broader features of the topography had l>eeu shaped, and the agency l>y which it was dei)Osited was nlO^"ing ice, as will be explained a little later.

THE EIVEK AND THE GORGE.

From Lake Erie the Niagara Eiver runs over a low sag in the ridge of Corniferous limestone. Where the current crosses this

rocky barrier, it is rajad and dis- turbed. Thence for fifteen miles it flows alxive shales, but rarely touches them, the banks and bed consisting chiefly of drift. The channel is In'oad, and the water glides along viith unruflied sur- face. Then, a little below the mouth of Chippewa Ci'eek, the Niagara limestone api>eai-s in the bed, and the whole habit of the stream is quickly changed. For a thousand yards it is a broad, roaring rapid, tumliling over one ledge after another with tunmltu- ous haste; and then it pours over a precipice to the bottom of a narrow, deep, steep-walled gorge. For seven miles it courses, with alternation of deep, boiling

Fio. 4. — Biril's-eye View ot' th agara River from Lake (!)utario.

Ni-

Be- pools and narrow, violent rai)ids,

yoiul the Ontario fihore are tlie Lower thrOUgll this gOrgC, wllOSe steei) Plain. Escariiinenf. I'pper Plain, and ,, '^ .. , '^t '" i ,

Lake Erie. walls ot rock tljeii turu abruptly

THE lUVER AND THE GORGE. 209

to the right aud left, and merge with the face of the esearp- meut. Thence to Lake Ontario the width is moderate, and the current is strong and deep between steep banks of red shale capped with drift.

Thus for two thirds of its journey across the upper plain the river travels on top of the plain, and then for the remaining third it runs from two hundred to three hundred feet below the plain in a narrow trench. This contrast is the geographic fact on which scientific interest in Niagara has centered, and its im- portance is not readily overestimated.

The walls of the trench are vertical clitfs in their upper part, and are there seen to be composed of the same limestone that underlies the plain. The limestone cliffs are of moderate height,

Fig. 5. — Cross Seetions of Niagara River.

n, two miles below tbe escarpnient ; 6, in the narriiwest part of the jjorge ; c, iu a limad part of the gorge ; </, two iiiik's alio\e thu falls. Scale, about 2,000 feet = 1 iucli.

and from their base there usually starts a talus or apron of frag- ments, which descends to the river's edge. The general appear- ance of the gorge is fairly illustrated by the view in Fig. 7. Heiv and there the talus is scant or altogether absent, so that tlic strata can be seen; and wherever they can ])e seen, examination shows the two sides to have the same l)eds, in the .same order, and at the same heights. First come gray shales about fifty feet thick ; then a Ijlue-gray limestone full of fos.sil shells, and ten or fifteen feet thick. This is the Clinton limestone of geologists; and it is so firm, as compared with the beds immediately above and below it, that rain and fi'ost have affected it less, and it projects beyond its neighbors. There are several places where the edge of the bed is a cliff, though the adjacent shales are covered by fallen fragments (Fig. 6). -Next below are gi-een-gray shales, with thin limestone beds, and a soft, gray sandstone, the whole occupying a vertical space of about thirty feet ; and then the color changes to a Ijright red, which characterizes the lower beds. The.se are chiefly shales, liut there are soft sandstones among them; and there is one hard sandstone bed, of a pale

210

NL'.GAKA FALLS AND THEIR HISTOKY.

gray color, Avhicli stands out iironiiiiently like the Clinton lime- stone, and for the same reason. It is twenty feet or more in thickness, lies one hundred and twenty feet below the Clinton limestone, and is called the qnartzose sandstone (see Figs. 10 and 21). The observer who sees these various rocks, hard and soft, gray and red, matched bed for bed on the ojiposite sides of the

Fig. C. — Cliff and Talus of Aiiierieau Bank above the 'Wliirlpool.

The Xiatrara liiuestoui' appears in the upper oliff; the Cliutou, iu the lower. The quartzoee saudstonc is not seen, beiuK below the water.

gorge, and who studies them at the angles of the walls, so as to realize that each is a great level jilate, which, if continued through the air, would bridge the chasm to its companion in the opposite waU, never doubts that the rock lieds were oi'igiually continuous, and that the gorge is of later origin. As to the way iu which the gorge was made, there has been some difference of opinion. One or two writers have thought it was a crack of the earth ^•iolently rent apart, and one or two others have thought it was washed out by ocean tides; but the prevailing opinion is that it was made by the liver that flows through it, and tliis opinion is so well grounded that it is hardly worth while to consider its rivals iu this place. The agency of the river is shown by the modern recession of the cataract, liy banks, terraces, gravels, and shells, marking earlier positions of the liver bed, and by a cliff

THE RECESSION OF THE CATAKACT.

211

over which ijavt of the liver ouce poured as a cataract. It is qualified by a buried channel belonging to an earlier and differ- ent system of drainage. As these evidences are intimately con- nected with the history of the cataract and livei-, they will be set forth somewhat fully.

THE RECESSION OF THE CATARACT.

Modern Recession. — The cataract is divided unequally by Goat Island. The part on the southwestern or Canadian side is the broader and deeper, and is called the Horseshoe Fall ; the

i-'ii

-The UuriTL' bclu'.v lln

Wliirli.uul, with i'lirl Foreground.

■I llil' Wllllll'Hil

Other is the American Fall. As shown by the map (Fig. 15), the Horseshoe Fall is at the end of the gorge ; the American, at its side. The cliff over which the water jwurs is from one hundred and forty to one hundred and seventy feet high, measui-cd from the water of the i-iver below. It is composed of the Niagara limestone at top, from sixty to eighty feet thick ; and the shales,

21J

NUGAIJA FALLS AXD THEIlt HISTOUY.

etc., beneath, as already described. At the edge of each fall, where one can look for a distauce under the sheet of desceudiug watei", th(> limestone projects like a cornice beyond the •wall of

Fig. S. — The Horseshoe Fall, from the Cauadiaii Bank.

shale; so that there is a stiip of the upper rock which is not directly supported by the lower, but is sustained by its own strength. From time to time portions of this cornice have been seen to lireak away and fall into the \wo[ of water below, and other fallings have made themselves known by the earth tremors

Fig. 9. — The Am.

lU i'aii. Irum tiic ( ;iu;uH:iu BaiiK.

they produced. Usually the falling masses have been large ; so that their subtraction has produced conspicuous changes in the contour of the cataract, and their dimensions have Ijeen esti- mated in scores of feet. Nearly all liave broken from the cliff under, or at the edge of. the Horseshoe Fall. As these catas- trophes depend on the iirojection of the limestone ^^•ithont sup-

THE KECESSIOX OF THE CATABACT.

•213

port, ^ve are warranted in supposing that it is gradually depriveil of support by the removal of the softer rocks beneath ; and, al- though it is impossible to see what takes place amiil the feaif ul rage of waters, we may properly infer tlint that very vioh^nce makes the cataract an engine of destruction by which the shales are battered and worn away. Under the middle of the Horse- shoe, where the pouring sheet is at least twenty feet thick, its force is so great as to move most, or perhaps even the largest, of the fallen blocks of limestone, and by rolling them about make them

serve as weajjons of attack.

Fig. lU. — I'l-ofile ami Set-tioii at Mid- dle of Hoi'seslioc Fall, showing Anauge- In 1S27 Capt. Basil Hall, of ment of Uoi'ks and I'l-olialde Depth of

the British Navy, made a care- ^''."'' "'"^^■■' '•'"■ ,. ,.

' ' N.I,., Niairara Inuesttiiii' ; CM... Clinton lime-

ful drawiuy of the Horseshoe stone ; CJ.S.. (luartzo.si- sandstone. Bcale, C' 3U0 feet = 1 Inch.

Fall by the aid of a camera lucida.

The use of that instrument gives to his drawing a quality of accuracy which constitutes it a valualjle record. Sixty-eight years afterward, in 1895, a photograph was made from the same spot, and our illustrations (Figs. 11 and 12) bring the two pic- tures together for comparison. The bushes of his foreground have grown into tall trees which restrict the view, l>ut the re- gion of greatest change is not concealed. A vertical line has been drawn through the same point (Third Sister Island) in each picture to aid the eye in making the comparison. The conspic- uous changes are the broadening of the gorge by the falling- away of its nearer wall, and the enlargement of the Horseshoe curve both by retreat to the right and by retreat in the direction away from the spectator. In 1842 Professor James Hall, State geologist of New York, made a careful instrumental survey of the cataract for the jiuri»ose of I'ecording its outline, .^o that sub- sequent recession might l>e accurately measured l>y means of future surveys. His work has been repeated at -various times since, the last survey l)eing by Mr. A. S. Kibbe, assistant State engineer, in 1890. The outlines, as determined by these surveys, are reproduced in the chart on page 216 (Fig. 18), which shows that the greatest change has occurred in the middle of the Horse- shoe curve, where the thickness of the descending stream is

n4

NIAGARA FALLS AND THEIi; HISTORY.

THE KECESSION OF THE CATAKACT.

21G

XIAGAKA FALLS AXl) THEIU HISTORY.

Fig. 13. — Outlines of the Ci-est of the Horseshoe Fall.

The vertical and horizontal lines are 2tX) feet apart.

greatest. In that regiou about two huiidved and twenty feet of the limestone bed have been earned away, and the length of the gorge has been increased by that amount. From these data it

has boon computed that the cataract is making the gorge longer at the rate of between four and five feet a year, and the general fact determined by the observation of faUmg masses and the comparison of pictures thus receives a definite expression in the ordinary tenns of time and distance.

The agent which has wi-ought such important changes during the brief period to which careful observation has been limited is manifestly able to hoUow out the entire gorge if only granted enough time, and the theory which ascribes the making of the gorge to the work of the falling- water is thus strongly supjiorted.

Mode of Recession. — Before passing to other facts bearing on this point, it is well to caU attention to certain peculiarities of the process whereby it difl:ers from the nonnal process of cataract erosion. Pure water has little jiower to erode solid rock. It can pick uj^ loose particles or roll them along; but Ann, coherent rock cannot be broken by so soft a tool. Rock is, indeed, worn away by rivers, and the erosion accomplished in this way is enomious ; but the water does it indii*ectly by carrying along rock fragments which rub and pound the solid rock of the river bottom. The rock fragments are of the same material, generally speaking, as the solid rock, and they wear it away just as diamond dust wears the solid gem. As already pointed out, the Niagara is peculiar in that its cm-rent carries no rock fragments. The geographic work peiformed by the cataract is jn-actically dependent on the tools furnished by the blocks of fallen limestone. It is therefore of prime importance to the work of the cataract that it shall be able to roU the lime- stone fragments about, and thus grind them against the river bed. A .study of the different parts of the cataract, comparing one ^with another, shows that the water has this power only where its body is great ; namely, in the middle part of the Horse- shoe curve. Under each edge of that fall and under the Amer-

THE HECESSIOX OF THE CATAKACT.

217

ican Fall great blocks of limestone lie as they have fallen, mani- festly too large to be moved by the moderate streams that Vjeat against them. Some of these are shown in the genei-al view of the Horseshoe Fall (Fig. 8), and more clearly in the view of the Ameiicau Fall (Fig. 9). The block at the extreme right of the Ameiican Fall is also pictured in Fig. 14. The resistance opposed by these blocks makes - -

the I'ate of erosion of the Ameiicau Fall compara- tively sloAv. In fact, it is so slow that attempts to measure it have thus far been unsuccessful, be- cause the changes which have taken place in its outline between the dates of surveys have been little greater than the inaccu- racies of the surveys. Where the heaviest body of water pours down, the blocks are not mereh' moved, but are made to dig a deep hollow in the shale. The i>reeise depth cannot l)t' measure(l, because the mo- tion of the water is there too violent for sounding ; but a little farther down the rivei', where the cataract perfomied its woi-k only a few centuries ago, the plummet shows a depth of neaiiy two hundred feet, and it is proba])le that the hollow directly under the Horseshoe is not shallower than .that. The general fact ai)pears to be that in the center of the main stream the water digs deeply, and the Ijrink of the fall recedes rapidly. After the gorge has been lengthened by this process, it is some- what widened by the falling in of its sides; and this falling in is in a measure aided by the thiinier water streams near tlie banks, which clear away the smaller limestone fragments, though leaWng the larger. After the cataract has altogether passed, the cliff is further modified by frost. The wall of shale, being wet by spray or rain, is exposed to the cold air of winter, and the water it contains is frozen. The expansion of freezing breaks the rock, either crumbling it or causing flakes to fall

i'li.. 14. — Th.' -K.n-k ul Agi-N" :t Falliji lllovk

of Niagara Limestone at the Soiitheni Edge

(if tlie Aineriean Fall.

218

XIAGAKA FALLS AXD THEIK HISTORY.

away. lu this way the shale is eatou Itaek, and the Uiuestoiie above is made to fall, uutil enough fallen fiagments have been accumulated to protect the remainder of the shale from frost,

after which time the process of change becomes exceedingly slow. Thus two different modes of cataract recession are illustrated by the two faUs of Niagara. They resemble each other in the most essential particiUar, — that the soft shale beneath is worn away, and the hard limestone above falls for lack of supi^ort, — Itut they differ widely in other re- spects. In the recession of the Horseshoe Fall, the blocks of limestone are pestles or gnnding tools by which the shale is beaten or scoured away. In the reces- sion of the American Fall, the limestone blocks have no active share, but are rather obstructive. The falling water, striking them, is splashed against the cUft', and this splashing is the only foi'ce continually applied to the shale. In the spring, ice cakes are drifted from Lake Erie into the entrance of the river, and float to the falls. Borne with the water, they, too, nmst be dashed against the cliff of shale, and, though softer than the shale, they probably helj) to dislodge it. The recession in one case is far more rapid than in the other, the difference being explained piimarily by the difference in the volimie of the water.

Old ErvEK Baxks axd Gka^'els. — As just explained, the re- treating cataract lengthens the gorge most rapidly in the middle of the stream, where the water is deepest. As the gorge is ex- tended, the current turns toward its head from Ijoth margins.

	^
	^
1	jl
	^f^-^
\ ^'/ffJ	^fp>
Voster f§X//	1
~^ ^"^5^ Wl -^v"^^^
^---, T*^ ^^hirlpool
■^ j \^^ !*hrrlpool Rapids
7 /I " " °	lagei
J if
y» >*....»t. 8..ag.
■ m ^vi^American F*II
^ftrs« shoe •■ I ^ ^"^^^^ ^-ihr- fill ;\ri^i!i^ ^—^^	X___
\% Upp,r '	^=53.
" '^-'- ^^^ '1

Fig. 15. — The Xiagara Gorge, showing Physical Featui'es.

Old river banks are shown by dotted lines ; shell localities, by crosses.

THE RECESSION OF THE CATARACT.

•Jl!>

and portions of the river bed on citlicr side are thus fjjradually abandoned by the watei-. After these strips of rivei- V)ed liave become dry hind, they retain certain featnres by which tliey can be recognized. Usually the whole of the di-it't is washed away as far as the water extended, so that the rock is 1)are, or nearly bare ; and the edge of the undisturbed drift at the margin of this strip of bared rock has a steep slope, which so closely resembles the modern banks of the river above the cataract that the imagina- tion readily restores the former outline of ihe \vati*r (see Fig. 1(>).

1'.. -u;a i...L. r...:

Kiver Be<l, One Mile North of Ana-iifiiu Fall.

Sometimes the I'iver, after running for a while at one level, has been drawn down to a lower level, and the change has caused a second bank to be produced, the space between the first and second banks standing as a bench of land, or terrace. At some points thei'e ar(» two or three such terraces. Along the greater l)ai-t of the gorge these old banks can 1)e found on both sides, and there ai'e few spots where they do not survive on one side ov the other. The farthest point to which tliey can be ti'aced downstream is about half a mile tVnm the end of the gorge, and

•2'2()

NIA(;AKA falls and THEIK HlSIOltY.

they thus serve to show that all the veniaiiider of the gorge has heeu wrought during the life of the river; for it is evident that the river could not run on tlie ujihuul while the gorge was in existence.

In a few cases, where the top of the limestone lies rather low, the old river beds are not excavated down to the rock, but their terraces are |)artly carved in drift. In yet other places the old river not only carried away material, but made additions, leav- ing a deposit of gravel and sand that had been rolled along l)y the current. In this gravelly de]iosit, shells have been found at a number of places, and tlicy are all of such kinds as live in the (piieter parts of the river at the present time.

On the chart on page 218 (Fig. 1')) the most important of the old river banks are shown, and also a number of spots at which shells have been found in the river gi-avels.

Foster Flats. — Al)out two miles and a half soiith of the escarpment the goi'ge assumes a peculiar phase not elsewhere seen. It is imusually wide at the top; but the river is quite narrow, and runs close under the cliff on the eastern or American side. On the ('anadian side an irregular lowland lies Itetween the cliff and the river, but this is encroached on by a quadran- gular projection of the cliff. The lowland is Foster Flats; and

Fi'i. 17. — Binrs-i've View of Foster FlatK, lonkiiif; Soutliwest (Forests omitted).

THE KECESSIOX OF THE CATAKACT.

the clilif pvojectioii, Wiiitergveeii Flat. These and other features of the locality are portrayed in the bird's-eye view (Pig. 17), and also in the map (Fig. IS). The niaj) represents the slopes of the land l»y means of contour lines, or lines of ecpial height, drawn at vertical intervals of twenty feet.

Wintei'green Flat is a platform of limestone a little hdowthe genei'al level of the jdain, and separated from the j)laiu hy a steep hluff. This l)lufit' is one of the old I'iver banks, very simi- lar to the one pictured in Fig. Ki, and the i)latform is part of the river's l)e<l. Following the direction of How — jiai-allel to the bank — to the point A (Fig. IX), the observer finds himself on the brink of a cliflf over which the water evidently descended in a cataract ; and before him, extending from the foot of the cliff to the point />', is a de- scending valley with the form of a river 1 n^d. From Winter- green Flat onlj^ its general shape can be made out, as it is clothed with forest; but wlien one gets down to it, he finds it a northward-sloping ]ilain, bounded by steej) sides, and strewn here and there with great fallen blocks of lime- stone which the river current could not remove. The left

Fio. 18. — Map of Foster Flats.

bank of this channel has the ordinary ])rofile of the wall of the gorge, — a cliff of the Niagara limestone at top and a talus slope below, covered by blocks of tlu^ same rock. The right wall is lower, rising at most but fifty feet above the channel, and gra<lu- ally disaiijicaring northward. Tt is merely the side of a low ridge which separates the abandonc(l channel from the river bed at the cast. Its siirface is exceedingly rugged, being covered by huge blocks of limestone, so that the ridge seemingly consists of a heap of them ; but then^ is doubtless a nucleus of undistiu'bed shale, with a remnant of the Clinton ledge. EastM-ard from Wintergreen Flat there is a continuous descent from the lime- stone cliff' to th(> river; but this is less stee]) than the ordinary talus slope of the gorge, and it is cumbered, like the ridge, by

lljL' NIAGAKA FALXS AND THUlIt HISTORY.

liloi'ks of liinestouo. Theio is an obscure tevraoe at about the level of tli»' Clinton limestone, and there are other irregular ter- races on the st)Uth\vard prolongation of the slope.

The history which appears to afford the best explanation of these features is as follows : When the cataract, in its recession fi'oni the escaipment, had reached the point L', it was a broa<i waterfall. Just above it, occupying the position (' — 1), was a narrow island, dividing the river as Goat Island now divides it. On reaching the island, the cataract was sepai-ated into two parts corresponding to the present Horseshoe and American falls, only at that epoch the greater body of water passed on the Anici-ican side of the island, so that the American Fall retreated upstream the more rapidly. When the Cauadian Fall reached the head of the island, the American had just passed it, and part of the sheet of water on Winteigreen Flat was drained eastward into the gorge opened by the American Fall. The Canadian Fall, through the loss of this water, became less active, and soon fell out of the race, leaAnug the cliff at A to record its defeat. For a time there was a cataract at E falling oA-er the west wall of the gorge just as the modern American cataract falls over the east wall. The island was not bi'oad enough to survive as a mommient. After the cataracts had passed, its pedestal of shale was crumbled by the frost, and the unsupported limestone fell in ruins. As the main fall retreated still farther, the western portion of the water sheet was withdrawn from "Wintei'green Flat, occui)ying a position at F, and at the same time the stream near the Canadian shore acquired greater volume, so as to i-ecede rapidly toward G and thus broaden the channel. Pro])ably at about the same time the whole amount of watei' in the river was increased in a manner to be considered latei'.

"\^Tien the reader next visits Niagara, he will find himself fully repaid for his pains if he will go to this spot, and examine these features for himself. It is peculiarly impressive to stand on the silent brink of the old wateifall and look down the diy channel, and it is no less impressive to enter that channel and wander among the blocks of rock Avhich record the limit of the torrent's power to transport. It is evident that here the cataract did not hollow out a deep pool, as under the Horseshoe Fall of to-day, but was rather comparable in its mode of action to the American Fall, though perhaps somewhat more vigorous. The slope eastward from Wintergreen Flat probably corresponds

THE KECESSIUN OF THE CATAKACT. JJ.'J

closely with what oue woukl hud under the Amerieau Fall if the rivev were stopped aud the pool drained.

Thus Foster and Wintergreen flats repeat the story told by the old river banks and the shell-bearing gravels. There was a time when there was no gorge, but when the i-iver i-au over the top of the plain nearly to its edge ; and since that time the gorge has been gradually dug out by tlie power of the jilunging water.

Beiunning of Kecessiox. — When the geogi'aphfi- notes that some natural process is producing changes in the features of the land, he naturally looks backward, if h(> can, to see what were the earlier features which i»ivcedcd the changes in pi'ogress, and looks forward to see what will be the eventual condition if changes of the same sort are continued. The tracing of the his- tory of change in either direction is apt to be difficult, l)ecause it is not easy to tell what allowances to make for changes of cir- cumstance or condition. In tracing the early history of Niagara such difficulties as these arise, but there is one difficulty which is not altogether unfortunate, because it leads to the discovery that the Niagara history is definitely related to one of the most interesting events of the geographic development of the conti- nent.

Having learned from tlic cataract that it is engaged in the work of gorge making, and having learned from the old river beds along the margins of the gorge and fi'oni the old cataract cliff at Foster Flats that this work of gorge making has been carried on through the whole length of the gorge, we are cari'ied back in imagination to an ei)och when the river traveled on the upper plain all the way from Lake Erie to the escarpment, and there descended. The general history is cleai'ly traced back to that point, but there it seems to stop abruptly. We may com- pare the river to an artisan sawing the plateau in two. The work goes on mei-rily and the saw cut is still short. As geolo- gists reckon time, it is not long since the task Avas begun. But Nature's artisans cannot stand idle; while they live, they must work. So, before this task was liegun, either the stream had some other task or else there was no Niagara River. It seems impossible to suggest any otluM- task, and all geogi'ai)hers are agreed that theiv was none. The river's first work was the dig- ging of the gorge, and the date of its beginning was the date of the river's beginning.

The nature of this beginning, the series of events whii-h led

'2'2i XIAtiAKA I'AI.I.S AND TIIKIU HISTOltV.

Up to it, Of, ill otluT words, the ciUise of tiic river, was long sought ill vain; ami an interesting cliapter luiglit lie written on tile fruitless search. The needed light Avas an understanding of the origin of the drift; aii<l it was not till a young Swiss geolo- gist, Louis Agassiz, brought from the Alps the idea of a drift- bearing iee field that the discovery of Xiagnra's jiedigree became possible.

PEVELOl'MENT OF THK LAlltENTIAN EAKES.

The Ice Sheet. — The history of the great Canadian glacier is a large subject, to which some future monograph of this series will doubtless be devoted. Any account t)f it whi<di can be given here must needs be inade([uate, yet a full understanding of Niagara cannot be reached without some knowledge of the glacier. In the latest of the geologic periods the climate of North America underwent a series of remarkable changes, be- coming alternately colder and warmer. While the general tem- peratui-e was low, there was a large area in Canada over which the fall of snow in winter was so deep that the heat of summer did not fully melt it ; so that each year a certain amount was left over, and in the course of centiiries the accumulation ac(juired a depth of thousands of feet. By pressure, and l>y melting and freezing, the snow was packed, and welded into ice. When the climate again became warmer, this ice was gradually melted away; but while present it perfornie(l an imiiortant geographic work. Ice in large masses Is plastic; and when the ice .sheet had become thick, it did not lie inert and motionless, but spread itself outward like a mass of iiitch, its edges slowly jiushing away from the central tract in all diivctions. This juotion car- ried the ice border into regions of warmer climate, where it was inelte(l; and for a long ])eriod there was a slow but continuous movement from the central region of accumulation to the mar- ginal region of waste l)y melting. The principal region of ac- cumulation was north and northeast of the Great Lakes, and the flowing ice jiassed over the lake region, invading all our Northern States. Where the ice jncssed (m the grcmnd, it envel- o])ed l)owlders, pebbles, and whatever lay loose on the suiface; and as it moved forward, these were carried with it, being dragged o\er the solid rock, ami scra])ing it. Thus the country was not merely swept, but scratclie(l and jilowed, with the result that its .surface was worn down. The aniount of wear was not

DEVELOPMENT OF THK I.AIKENTIAN LAKES. 2'J.)

everywhere the same, ))ut varied from place to place, and many basius were hollow(^(l imt. AVIhmi tln^ general climate Ijecanie gradually warmer, the was^te of ice near its margin exc-eeded the supply, and the extent of the sheet was diminished. When the ice was gone, the stones and earth it had picked up and ground up remained on the land, hut in new positions. They were sjiread and hea2)ed irregularly over the surface, constituting the mantle of di'ift to which reference has already been made. Thus by the double process of hollowing and heaping, the fai-e of the land was I'emodeled; so that when the rain oiire moiv fell on it, and was gathered in sti-eams, the old water ways were lost, and new ones had to be found.

This remodeling ga\'e to the Laui'eiitian system of watei- ways its abnormal chai-actei-, supplying it with abundant lakes and waterfalls. Not only wei'e the Great Lakes created, l)ut a multitude of minor lakes, lakelets, ponds, and mai'shes. if the reader will study some good map of the rnite<l States or of North America, he will see that this lake district includes New England also, and 1»y tracing its (>xtent in othei' tlirectioiis he can get a fail" idea of the magnitude of the ice sheet.

The lakes have had a marked intluenc<' on the history and iuciustries of maidvind. Still water ]nakes an easy roadway, and the chain of (Jreat T^akes not only guided exploration and early settlement, but has (h'termined the chief routes of commerce ever since. The most easterly of the ice-made basins, instead of holding lakes, receive arms of the sea, giving to New York and New England some of the l)est harbors in the world. Each cat- aract is a water powei-, and the lakes and ponds upstream ai-e natural storage ivservoirs, holding l»ack Hoods, and doling the water out in time of drought. So Chicagc) and New York City are the centers of trade, and New England is a land of hum- ming spimiles and lathes, becaus(> of an invasion long ago by (Canadian ice.

The district of the Niagara lay far within the extreme limit of the ice, and the (b-ift there lying on the rocks is part of the great ice-spread mantle. Wherever that drift is freshly removed, whether by the natural excavation of streams or the artifi<'ial ex- cavation of (luarrymen and builders, the rock l)eneatli is found to be polished, and covered by pai'allel scratches, the result of rubbing by the ice and its gritty load. These scratches show that in this particular district the ice moved in a direction about

L"Jt)

NIAGAKA FALLS AND THEIK HISTOKY.

30° west of sdutli. Tliey can lie seen on tlie western l)vink of the gorge four hundred yards below the raihoad suspension lii'idge, in the beds of several creeks near the Whirl jxxvl, and at various (juarries above the es('ari)nH>nt. The l)est oppoi-tunity to study them is at a group of quarries near the brink of the eseai'pnient, about two miles wi^-^t of the river.

Ice-dammed Lakes. — During the period of final melting of the iee sheet, when its southern margiu was gradually retreating across the I'egion of the (Ireat Lakes, a number of temporary lakes of peculiar character were formed. In the accompanying

sketch map of the Great Lake region (Fig. 19) the broken line marks the position of the southern rim of the 8t. Law- rence basin. It is the water- shed between the district ilraining to the St. Lawi-ence and the contiguous districts draining to the Mississippi, Ohio, Husquehanna, and Hud- son. When the ice sheet was ^"'- "n?^!;i;,Se DiJ^r^r"" *'"'" gi-^atest, its southern mai-gin

The watershids liouiidiiig tlie drainafre (Ustviits "^y SOUtll ot tlllS Watershed. ;nvrepresen,...n,.vaotte,l and .n„k.„ lines. rj.,,^ ^..^j^^ ^^.^^-^.j^ ^.^^,j ^^^^ ^j^^

ice, uniting with the water made by melting ice, ran from the ii-e held on to the land, and flowed away with the rivers of the land. Aftei-ward, when the extent of the ice ha<l been some- Avliat reduced, its margiu lay partly beyond and paitly within the basin of the lakes; but the water fi'om it could not flow <lown the St. Lawrence, ])ecause that valley was still occu- l>ied l)y the ice. It therefore gathered between the ice front and the watershed in a series of lakes, each of which found outlet southward across some low jioint in the watershed. To see this clearly may require some eifort of the imagination. The reader should bear in mind that the watershed is not a sim- ple ridge, but a rolling ui)land f)f varying height, with here and there a low pass. The St. Lawrence basin is not simple and r<>gular in form, but is made up of many smaller l)asins separated by minor uplands or watersheds. Some of these watersheds are shown on the map. When the ice occu]>ied part of minor basins, it acted as a dam, holding the water back, ami making

DEVELOPMENT OF THE LAURENTIAN LAKES. '2'27

it fill the basin until it could How in some other direction. As the position of the ice front changed, these lakes were changed, being made to unite or sepai'ate, and often to abandon one chan- nel or outlet when another was opened at a lower level. Some- times there were chains of lakes along the ice margin, one lake draining to another across a minor waterslied, and the lowest discliarging across the main watershed.

AVherever water rail from a lake, it niodified the suiface. The loose drift was easily moved by the current, and each stream (juickly liollowt'd out for itself a channe], — a trough-like passage with flattish bottom and steejj sides. When tlie lakes afterward disappeared, the channels lost their streams, but their fonns i-e- mained. They are still to be seen in a hundred passes among the hills of the Northern States. The larger and longer-lived of the lakes carved by their waves a still more conspicuous record. In ways explained by Professor Shaler in tlie fiftli monograph of this series, the waves set in motion liy storms cut out sti-ands and cliffs from the drift and Iniilt up barrier beaches, so that after the lake waters had dejiarted there were terraces and ridges on the hillsides to show where the shores had been. Many of the old channels have been found, some of the old shore lines have been traced out and marked on maps, and by such investi- gation the history of geographic changes in the (ireat Lake region is gi'adually l^eing learntMl.

At one stage of that history there was a long lake occupying the western part of the Ontario basin, much of the Erie, pai-t of the Huron, and ]>robably part of the ^licliigan. Its outflow crossed the main watershed at Chicago {(\ Fig. 19), and its east- ern extremity was near Batavia (/i) in westei-n New York. The ice mass filled the greater p.irt of the Ontario basin, and kept the water from escaping (>astward. When it melted from that region, the water shifted its outlet from Chicago to a low pass at Rome (R), where it discharged to the Mohawk valley. This change lowei'ed the lake surface sevei-;il liuudi'cd feet, and, by uncovering watorslieds that had before Iteeu submerged, sepa- I'ated the Huron, Erie, and Ontario basins, and three lakes took the place of the single long lake. In the Huron basin was a lake half walled by ice; in the Erit; basin. Lake Erie; au<l in the Ontario basin. Lake Irocpiois, an ice-dammed lake with its outlet at Rome.

The draining away of so larg(> a body of water occupied some

•2'2f< XLiGAlU FALLS AND THEIU HISTOKY.

time, SO that the lake level was gvadiially lowered. Wiieu it reached the i»ass between the Erie and Outano basins at Hutfalo, and Lakes Erie and Irociuois were thereby i)arted, the Erie level could fall no lower, but the Iroquois eontiniied ilowuward. As soon as there was a ditferenee of level, a stream began ti> How tVoni Lake Erie, and that stream was the infant Niagara, newly born. It was a short stream, because the edge of the Irotjuois water was close to Bulfalo ; but it grew longer day by day, as fast as the Iroquois edge receded. It had no cliaunel until it made one, but its growing end, in following the retreating lake, selected at each instant the direction of steepest slojie; and as the slopes had l)een fonued by the glacier, it may lie said that the glacier predetermined the course of the river.

During some centuries or millenniums of its early life the river was shorter than now, because the Ircxjuois Lakn flooded more land than the Ontario, and kept the river nearer the escarp- ment; lint in cour.se of time the ice dam disappeared, the lake outlet was removed from Rome to the Thousand Islands, part of the lake bottom was laid bare by th.e retiring water, and the river stretched itself over the broadened plain. It grew, in fact, to be a few miles longer than now, and theiv were other changes in length : but the entii'e story is too long and intricate for these [lages.

The C'antim; of Baslns. — The geographers who have mapped the glacial lakes by tracing their shore lines have also measured the heights of these lines at many jioints. From these measure- ments they have found that the lines are not level. The surface of each ice-dammed lake wa.x, of course, level, and its waves, beating on the shores, carved beaches and strands all at the same level. But these abandoned stran<ls. preserved as terraces on the basin slojies, are not level now ; and it is therefore inferred that the earth itself, the rocky foundation on which the terraces rest, has changed its fonn. The idea of earth m()vements, the slow rising of some districts and the sinking of others, is not new: but, until these old shore Hues were stiuiied, it was not known that such changes had recently affected the Lake region.

The departure of the old shore lines from horizontality is of a sy.stematic character. They all rise toward the north and east, and fall toward the south and west. The amount of this tilting or inclination is not the same everywhere, nor is it everywhere in precisely the same direction; but the general fact plainly

DEVELOl'MENT Ol' THE LACKENTIAN LAKES. 2'2\)

appears, that tlif uoitln-astcin jiortiou of the Great Lake district has been raised or tlie soutliwesteni portiou has been lowered, <>i' l)otl), several limidred feet since the epoch of these ice-dammed lakes, i.e., since the time when the Canadian ice sheet Wiis slowly nndting away. The ett'ec-t of this change Avas to tip oi- cant eacli lake basin, and the eflt'ect of the canting was similar to the effect of canting a hand l)asin containing water. In the hand basin the water rises on the side toward which the basin is tipped, and falls away on the opposite side. In the lake basin thei'e was a, constant supply of water from rain and sti^'unis, so that it was always filled np to the level of the lowest point of its rim, and the surplus of water flowed away at that jmint ; .vo. when it was canted, the changes in the extent of the lake were partly controlled by the outflow. If the outlet was on the north- eastern side of the basin, the southwesterly canting would make the water i-ise along its southwestern shore, the submerged area being thereby enlarged. If the outlet was toward the southwest, then the canting woulil draw the water away from the noilh- eastern slopes, and diminish Ihe submerged ai'ea. if the lowest point of the rim was originally on the northeast side, the canting might lift this part of the rim so high that some point on the southwest side would become lowest, and the ])oint of outlet might thus be changed fi'om north or east to south or west. The evi- dence of the old shores and channels shows that all these possible changes have actually occurred in the lake basins, and that some of them Nvcrc r(>late(l in an important wa\' to Ihe history of the Niagara- Kivei'.

The gi-adnal canling affected the size of l^ake Erie, Lake Ontario, and the temporary Lake Irocpiois, making each grow toward the southwest. "When Lake Erie was born, its length could not have lieen more than half as great as now, and its area was much smaller. The original Lake Huron may havt> had about the same size as the present lake, but its form and position were ditt'erent. Less land was covered at the south and west, more land at the north and east, and the outlet was at North Bay (iY, Fig. l!l). I>y the tipping of the basin the lake was made gradually to expand toward the west and south till at last the water reached the pass at the head of the 8t. Clair Eiver. Soon afterward the water ceased flowing through the North Bay outlet. The water then gradually withdrew from the northeast- ern region till finally the shores assunu'd their present po.sition.

230 NUGAKA FALLS AXD THEIR HISTORY.

At au earlier stage, while the North Bay district was blocked by the ice sheet, it is probable that the basiu had au outlet uear Lake Siim-oe (.S'), but the evidence of this is less conii)lete. If the Hurou water crossed the basin's rim at that poiut, it followed the Trent valley to Lake Iroquois or Lake Ontario; when it crossed the rim at Xortli Bay, it followed the Ottawa valley to the 8t. Lawrence ; and in each case it i-eached the ocean without passing through Lake Erie and the Niagara River. Thus there was a time when the Niagara River received no water from the Huron, Michigan, or Superior l)asins, but from the Erie basin alone. It was then a conipai'atively small stream, for the Erie basin is only one eighth of the whole district now tributary to the river ; and the cataract more nearly resembled the American Fall than the Horseshoe.

THE WHIRLPOOL.

The Whirlpool is a peculiar point in the course of the river. Not only does the channel theie make an abrupt turn to the right, but with equal aliruptness it is enlarged and again con- tracted. The pool is a deep oval basiu, communicating through narrow gateways with the gorge above and the gorge below. The torrent, rushing with the speed of an ocean greyhound from tlie steep, shallow passage known as the Whirlpool Rapids, enters the pool and courses over its surface till its headway is checked. The initial impulse prevents it from turning at once toward the channel of exit, and the current circles to the left in- stead of the right, following the curved margin of the pool, and finally descending under the entering stream so as to rise beyond it at the outlet. Thus the water describes a complete loop, a peculiarity of curi'ent (juite as remarkable and rare as the feats of railway engineering which bear that name. In the chart of the Whirlpool (Fig. 'JO) tlie sui-face cunvnts are indicated l>y arrows ; and some idea of the appearance of the currents may be obtained from the view in Fig. 7, where the swift incoming cur- rent crosses the foreground from light to left, and the exit cur- rent occupies the middle of the picture. In the smoother tract between these two visiljle currents the wat»>r rises after passing under the nearer. These cun-ents can be watched from any of the surrounding cliffs, and there is a fascination about them akin to that of the cataract itself and the Whiiipool Rapids.

THE WHIKLPOOL.

L':!l

Fio. a).— Tlie Whirlpool.

Roik is indicated hy ornsshnfcliiiiK; drift,

liy dots. Ari-ows indicate tlic

direction of cui-rcnt.

The gorge above, tlic gorge below, and two sides of the Whirlpool are walled by roek; but the remaining side, that op- posite to the incoming stream, shows no rock in its wall (Figs. 20 and '21). On the north side, the edge of the Niagara limestone can be traced to J (Fig. 20) with all its usual characters, Init there it disappears l)eneath the drift. The Clinton limestone disappears in a similar way just Vjelow it, and the quartzose sand- stone, which there skii-ts the mar- gin of the water, is a little more quicklj' covered, being last seen at 11. On tlie south 1)ank tlie Niagara limestone can be traced farther. Its edge is visil)le almost continuously to 1% and is laid bare in the 1)ed of a small creek at F. The Clinton bed is simi- larly traceable, with slight in- terruption, to D; and the quart- zose sandstone passes under the di'ift at ('. Where each rock ledge is last seen it points toward the northwest, and betrays no tendency to curve around and join its fellow in the opposite wall. In the intervening sjjace the side of the gorge seems to be composed entirely of di-ift. Sand aud clay, pebbles and bowlders, make up the slope; and n beach of bowlders margins the water from B to ('. It is inferred from this arrangement of rock and drift that there was a deep hollow in the plain before the drift was sjtread by the ice, the drift being depositeil in it and ovei- it until it was filled and covered. The parallel directions of the rock leclnes suggest that the hollow was part of a stream channel running northw(»stward ; and this interpretation is borne out not only by certain topo- graphic features two or three miles away, but by a study of the bed and banks of Bowman Creek (Fig. 15). That stream, Avhich rises two miles away, has carved a ravine where it approaches the Whirlpool. The noi-theast bank of the ravine (Fig. 20) seems to be composed entirely of drift ; but the opposite bank, th<mgh chiefly of drift, lays l)are the rock at a numlu'r of places, reveal- ing a sloping wall descending toward the northeast. The bed of the stream in general shows nothing but drift; bnt there is one place where the creek swerves a little to the southward, and

'2o'2 NIA(i.U!.\ lALLS AND THEIl! HISTORY.

for a tVw rods presses against tlic rock slope; and il lias tlicre made a small eiit into the rock, eascading at one i)oiut over a sandy ledge that is harder than the associated shale.

With the aid of this information, it is easy to understand the peenliar features of the AVliiil]K)i>l. The Niagara River did not seek this old channel and thus find an easy Avay northward, liut ran upon it ai-cideiitaily at one jioint. Its course on the jdain was determined for it hy the slojies of tlie drift, and the arrange- ment of tliese slopes happened to guide the water aci'oss the liuried channel at the "Whirlpool. Jn making the gorge from the Whirlpool to the escarpment, and also in making tlie u]ii)er part of the gorge, the river found liard rock to be removed; and it worked as a (puirr;^nuan, diggiug down lielow in the softer rocks with such tools as it had to use, and thus xiuderniining the lime- stone cap. At tlie Whirli:)ool there was no need to quarry, be- cause there was no limestone cap; and, to carry cmt the homely figure, the river merely d\ig in a gravel pit, shoveling the loose drift (luickly away. This work of excavation did not cease when a channel of the usual Avidth had been opened, l)ecause the angle in the course of the river set the current strongly agaiust the bank ()f drift, and caused it to clear out a liasin in the old channel. Had the drift been wholly, as it is partly, of sand, still more of it would have been carried out ; but it included large bowldei's, and these were sorted oiit and acciunulated mitil tliey made a sloping Avail or sheathing, Avliich covers all that part of the sand below the level of the ]>ool, and I'esists further en<'roach- nient by the water. So the peculiar form of the river at this place was caused by the old channel with its filling of loose saud and gravel. The looped cun-ent evidently depends on the pecul- iar shape of the channel. The water enters the pool with such impetus that it is carried past the outlet, and the retiirn current follows the bottom of the pool because that route is the easiest.

TIME.

Just under the escarpment where it is divideil by the river stand two villages, — the American village of Lewiston, the Canadian village of Queenstou. Lewiston is built partly on an old beach of l>ake Iroipiois, and near its steamboat wharf is a gravel pit where one can see the peVibles that Avere Avorn round by rolling up and down the old strand. That part of the escarj)-

JIMK. 233

nieut wliicli overlooks Lewiston is somewhat terraced, or divided into steps, aii<l was called "The Three Mountains" a century aj^o, when loads that liad l)i>eu l>r()U,ii:lit by boat to tlie landins; (Lewiston) wt-i-e toilsomely carried U[) the steep ascent on their way to other lioats jTlying ou the ui>per Niagara.

TheescarpiiK'nt alioveQueenstoii is called (^ueenston Heights; and from its crest rises Brock's monument, a slender shaft com- memorative of a battle between British and American soldiers. Within this sliaft is a spiral staii-case, and from a little chandjer near tht> top one can look through portholes far away in all directions. Eastward and westwaid runs the escarjiment, and the eye follows it for many miles. Sonthwai'd stretches the ujiper plain, diversified Ijy low, I'olling hills, and divided in the foreground by the gorge. In the still aii' a cloud of si)i'ay hov- ers over tlie catai'act, and a cloud of smoke at the horizon tells of Buffalo. Northward lies blue Ontario, and straight to its shore flows the deep-channeled, majestic Niagara, dividing the smooth green lowhunl into parts even more closely kin than the brother nations by which they are tilled. Beyond the watei-, and forty miles away, gleams Scarboro Cliff, where the lake waves are undermining a hill of di-ift ; and twenty or thirty miles farther the imagination may supply — what the earth's roundness con- ceals from the eye — a higher ujtiand that Itounds the Ontai'io basin.

The Brock monument, the Niagara gorge, and the Ontario l)asin are three pi-oducts of human or of natural work, so related to time that their magnitudes help the mind in gras})ing the time factor in Niagara history. The monument, measured in diameter by feet and in height l)y scores of feet, stands for the epoch of the white man in America. The gorge, measured in width by hundreds of yards and in length by miles, stands for the ejioch since the ice age. The l)asin, measured in width by scores of miles and in length by hundreds of miles, stands for a period be- fore the ice, when the uplands and lowlands of the region Avere carved fr<tni a still greater upland. The monument is half a century old; the gorge was begun some teTis or hundreds, or possibly thousands, of centuries ago; and the hollowing of the basin consumed a time so far lieyond our comprehension that we can only say it is related to the gorge epoch in some such way as the gorge epoch is related to the monument's half eentury.

The glacier made <'hanges in the Ontai-io l)asin, but they were

lj;;4 NIAGARA FALLS AND THEIU HISTOKV.

small in comparison with its oiij^ual size, and the basin is chiefly the work of other agents. Before the iilacial aye it was a river valley, and we may obtain some idea of its origin l)y thinking of the Niagara gorge as the beginning of a river valley, and trying to imagine its mode of growing broader. It has aheady been explained (p. 218) that the gorge walls fall baek a little after the cataract has lle^^^l them out, biit seem to come to rest as soon as all the shale is covered by talus. So nearly do they approach rest that their jjrofile is as steep near the mouth of the gorge as it is one mile below the cataract; l)Ut, in fact, they are not un- changing. Water trickling over the limestone cliff dissolves a uiiHutequantity of the rock. This makes it porous, and lichens take root. Lichens and other plants add something to the water that increases its solvent jiower. The fragments of the talus are eaten faster becaxTse they expose more surface. Each winter the frost disturbs some of the stones of the talus, so that they slowly move down the slope; and wherever the shale is laid bare, frost and rain attack it again. Thus, with almost infinite slowness, — so slowly that the entire age of the gorge is too short a unit for its measurement, — the walls of the gorge are retreating from the i-iver. At the same time every creek that falls into the gorge is making a narrow side gorge. The strongest of them has worked back oidy a few hundred feet (Fig. 13); but in time they, will trench the plain in many directions, and each trench will open two walls to the attack of the elements. Space forbids that we trace the 2>rocess further; Imt enough has been said to show that valleys are made far more slowly than gorges, and that the ancient shaping of the land into valley and upland was a far greater task than the comparatively modern digging of the gorge.

The middle term of our time scale, the age of the gorge, has excited great interest, because the visible work of the river and the ^■^sible dimensions of the gorge seem to afford a means of measuring in years one of the periods of which geologic time is composed. To measure the age of the river is to detennine the antiquity of the close of the ice age. The }irincipal data for the measurement are as follows: (1) The gorge now grows longer at the rate of fom* or five feet a year, and its total length is six or seven miles. (2) At the "\Miirlpool the rate of gorge making was relatively very fast, because only loose material had to be removed. Whether the old channel ended at the "Whirlpool, oi-

TIME. 235

extended for some distance southward ou the line of the river, is a matter of doubt. (3) Part of the time the volume of the river was so much less that the rate of recession was more like that of the American Fall than that of the Horseshoe. Some suggestions as to the comj^arative extent of slow work and fast work are to be obtained from the profile of the bottom of the gorge. AVhile the volume of the river was large, we may supjiose tliat it dug deeply, just as it now digs under the Horseshoe Fall (see p. 21G) ; while the volume was small, we may suppose that a deep pool

Fio. 21. — Longitudinal Section of the Niagara Gorge, with Diagram of the

Western Wall.

The base line is at sea levt'l. It is flivirted into miles. Wat^r, black; drift, dotted; Kint;ara

limestone in block pattein ; shales, lirokeii lines; !•", falls; I{, r.iilway bridges;

W, wbirlpool ; Foster, Foster Flats; E, escarpment.

was not made. Fig. 21 exhibits the approximate depth of the water channel through the length of the gorge ; and liy examin- ing it the reader will see that the depth is great neai- the mouth of the gorge, again from the head of Foster Flats to the Whirl- pool, and then from the bridges to the Horseshoe Fall. It is small, indicating slow recession, in the neighborhood of Foster Flats, and also between the Wliirl})Ool and the railroad bridges. The problem is complicated by other factors, but they are prob- ably less important than those stated.

Before the modern rate of recession had been determined, there were many estimates of the age of the river; but their basis of fact was so slender that they were hardly more than guesses. The first estimate with a better foundation was made by Dr. Julius Pohlman, who took account of the measured rate of recession and the influence of the old channel at the Whirl- pool ; he thought the river not older than 3,500 years. Dr. J. W. Spencer, adding to these factors the variations in the river's volume, computes the river's age as 32,000 years. Mr. Warren Upham, having the same facts before him, thinks 7,000 j^ears a more reasonable estimate. And Mr. F. B. Taylor, while re- garding the data as altogether insufficient for the solution of the problem, is of opinion that Mr. Upham's estimate sliould be multiplied by a number consisting of tens rather than units. Thus estimates founded on substantially the same facts range

236 NIAGARA FALLS AND THEIR HISTOKY.

from thousands of years to hundreds of thousands of years. For myself, I am disposed to agi-ee with Mr. Taylor, that no es- timate yet made has great value, and the best result obtainable may perhaps be only a rough approximation.

BOOKS OF REFERENCE.

Hall, Basil, R.N. Forty Etchings, from Sketches made with the Camera Lucida in

North America in 1827 and 1828. Edinburgh and London, 1829. H.\LL, Jasies. Niagara Falls : its Past, Pi-eseut, and R-ospective Condition (Nat.

Hist, of New York, Geology, Part IV.). Albany, 1843. Lyell, Charles. Travels in North America. London. 1845. Tyxdall, John. Some Observations on Niagara (Popular Science Monthly, vol. iii.,

1873). Pohlm.\k, Julius. The Life-History of Niagara (Trans. Am. Inst. Mining Engineers,

1888). Gilbert, G. K. The History of the Niagara River (Sixth Ann. Kept. Commissioners

State Reservation at Niagara). Albany, 1S90. KiBBE, Arc. S. Report of the Survey to determine the Crest Lines of the Falls of

Niagara in 1890 (Seventh Ann. Rept. Commissioners State Reservation at

Niagara). Albany, 1891. Shaler, N. S. The Geology of Niagara Falls (The Niagara Book). Buffalo, 1893. Spencer, J. W. The Duration of Niagara Falls (Am. Jour. Science, 3d Series, vol.

xlviii., 1894). Tatlor, F. B. Niagara and the Great Lakes (Am. Jour. Science, 3d Series, vol.

xlix., 1895).

MOUNT SHASTA, A TYPICAL VOLCANO.

By J. S. DiLLER.

THE VOLCANIC PKOCT.SS.

Heeds are wafted by the wind to fertile soils, where they ger- minate and take I'oot, and in time the migiity pine becomes the pride of the forest ; but in a few centuries it g!-ows old, declines, is blown over by tlie winfi'r st()rnis, (h'cays, and returns to the soil whence it came. Animals, little at l)irth, grow (o full stature and maturity, and in old age decline and pass away.

As with living things, so also with the glades and the hills, the valleys and the mountains. All are ever changing in course either of construction or of destruction, or of both. Each has its history more or less complete, embracing a beginning stage, a stnge of maturity, and a stage of d(>cadence.

Mount Shasta, a typical large volcano, is l)eyond the prime of its life. It is in the decline of its maturity. It has passed from a stage of vigorous growth into one of decadence, and is just be- ginning to sliow clearly the ravages of time. In order to prepare the way for a clearer understanding of the large volcano, it will be well to review briefly the volcanic i)rocess.

There ai-e many forces active in changing the features of the earth's surface. As explained in the first monograi)h, three" ways or processes in which these foi'ces operate may be distin- guished. They are riilcdi/isni, (Viastnipli'isni, and i/rmldfidn.

Vulcanism (Monograph No. 1, j'. -■+) modifies the surface by the transfer of material, generally in a molten eoudition, outward from the earth's interi<)r. In order to understand this transfei' it is necessary to consider the conditions within the earth.

Internal Heat. — In a boring made near Wheeling, W. Va., the temperatitre at various depths was obsei'ved as follows: at 1,850 feet, GS.TfjO F. ; 2,125 feet, 7().25o ; 2,990 feet, m.m° ; 3,482

(Copyrigtit, ISO.'i. l>y American Book ronijiany.) 2.S7

•2SS

MOUNT SHASTA, A TYPICAL VOLCANO.

feet, 93.60° ; 3,980 feet, 101.75° ; 4,402 feet, 110.15°. The teui- perature thus increased downward iit the rate of about 1 degi-ee for every 75 feet. Deep borings, wells, ami mines at many points

upon the earth's surfaee show that everywhere the temperature in- creases dowjiward in the earth. Although the i-ate varies with the place, the average increase is about 1 degree for every 45 to 75 feet. The rate of increase indicates that at a depth of 50 miles beneath the surface the temperature is higher than tliat reijuired to melt iron under ordinary conditions. The source of this internal heat, whether a residue from the oiigi- nal incandescent earth, or due to chemical action, or produced by the mechanical crushing of rocks, we need not stop to inquii'e.

"Water. — Rain falls on tlie mountain slopes. Some of it gathers into rills, runs into brooks, creeks, and rivers, and finally finds its way back into the sea whence it came. Another portion enters the soil, and undei- the influence of gravity passes thi'ongh the poi-es, cracks, and fissures of the rocks to various de]>tlis within the earth. On the lower slopes of the mcmn- tains, and in the valleys, much of the water which entered above re- appears in the form of springs, most of whicli are cool and refresh- ing. In some cases, however, the water penetrates so far into the earth before reappearing in s}ti-ings that it is warmed by the internal lieat. Thus warm springs, hot springs, and boiling springs are produced. In those l)oiling s})rings in which the outlet is large enougli to allow the heat to escape, the movements of the water are <'om])aratively

Geyser iu Action.

WAIKH. 231»

uiiifonn ; l)Ut in certaiti cases tlu; outlet is narrow in jtroportion to the length of the niore or less vertical tulie in the groiUK.l, ami tliere is not sulHcient opportunity for escape. The heat increases until the expansive force of the liigiily heated water an<l steam is sutticieut to produce an explosion. The overl>-iiig water and steam are thrown high into the air (Fig. 1) by the cniption. Such springs are t/ri/scrs^ and steam is the motive power in their

CI'KptioJ/.

The waters of hot sjirings may contain in solution carliouate of lime, silica, and othei- substances, whicli are dei)osited about the springs, making a mound. The one fi-om which the geyser, as shown in Fig. 1, issues is comjjosed of silica. Although .such mounds rarely attain a height of o\-er '20 feet, they are of suffi- cient physiographic importance to warrant mention here. As a class, they are among tlie smallest topographic eminences wliich are products of a process essentially volcanic, in its nature.

Next more important than eruptions of water in geysers are those of mud. A notable one occnired in 1S8H at Bandai-.san, in Japan. Large quantities of mud, saturated willi steam or higldy heated water under pressure, were developed a sliort distance beneath the surface. A great exjjlosion orcuri-iMl, removing the whole side of the mountain. A vast (piantity of steam escaped, and streams of mud flowed down the valley, damming water courses to form lakes, and destrojang a nund)er of \illages.

In true voh-anic action the material transferred from tlie in- terior of tlie earth to tlie surface is neither simple water, as in the geys(U', nor mud, as in the se?nivolcanic eruption at Bandai- san, but melted rock. It comes from greater depths tiian either of the others, where the tempei'ature is higher, and the rocks either in a molten condition or so hot that when the pi-essure u{)on them is relieved they fuse and becoine eiMii»tible.

In the geyser and eruptions of mud the material is impelled to tlie surface by steam. So also the molten rock material, or Diaf/Dia, within the earth is forced along lines of least resistance toward the surface l)y the absorbeij waters ami gases it contains. Other agents may, indeed, l>e tlie princi]>al on(>s in causing the upwelling of the magma frcnn within tlie eartli ; but to its absorbed gases are due many of the conspicuous phenomena attending the delivery of the material at the surface, where it solidifies, and becomes lara. The large qiiantities of .steam given

STATE NORMALSCHOOL.

L'40 MOUNT SHASTA, A TYl'lCAL VOLCANO.

off by volcanoes in eruiitioii arc illustrated iu Fig. l2 by tlie-cloiuls of vapor rising from the ontflow of lava of Vesuvius, in April, 1872. The whole mountain is involved in steam, rising from the molten rook which courses dowji its slopes.

Fig. ". — Mount Vesuvius in Eruiilimi, April, 18712.

Eruptions Intekmittent. — In the upbuilding of a great vol- cano like IMount Vesuvius the overflows are intermittent. Erup- tions wliicli transfer molten nintter from the interior to the sui'faee of the mountain to build it higher are not continuous. The brief epochs of actixaty are ordinarily separated by long periods of quiescence. For <'enturies before the beginning of the Christian era Vesuvius was without eruption; but in the year 79 it suddenly burst into vigorous action, and the cities of P()mj)eii, Herculaneum, and Stable, on its slopes, were over- whelmed and destroyed by the extruded material. Since then it has been in erui)tion many times, but the periods occupied by the extrusion of the molten matter have been very short as compared with the long intervals of repo.se.

Forms or Eruption. — Erujjtions are of two forms, — explo- sive, emd effusive. In the first form the material is blown to frag- ments and violentlv hurled into the air. In the second the

FORMS OF ERUPTION. 1241

magma wells up within the volcuuit- vent, and flows out over the surface in streams, forming cmdci'.s. These different forms of eruption are rarely distinct. Ordinarily tliey occur togetlu^i- in tlie same outburst, and the mountain 1o which thej' give rise lias a complicated structure.

The magma, full of absoi-bed gases, Water, or steam, distrib- uted tliroughout its mass, or perhaps most almndant in the upiiei- 2>oi'tion, im^u'lled l)y foi-ees not yet fully understood, rises toward the surface. When it gets near the surface, and the ])ressure is relieved, th(^ occhuh'd gases expand, often with ex- plosive effect, and teai' the viscous molten material into fine particles, which are hurled high into the air, to be spread far and wide over the land l)y the winds. During tlie gretit ei'uption of Krakatoa in August, lS8o, volcanic dust w.as thi-own to tlie height of over 17 nnles, and the surrounding country for many miles was covered with a sheet of volcanic sand and dust.

In many-cases the ejected fragments are coai'ser than dust, ranging in size from sand tlii-ough hipilli, various forms of cin- ders and bombs, to blocks of lava m;iny tons in weight. They fall al)out the vent from which the material is ejected, and, pil- ing u]), form a ciiidcr couc. Explosiv(> eruptions usually accom- pany the extrusion of viscous lava. Cinder (>ones generally have steep slopes, and funnel-slniped craters in theii' summits. They are abundant along the Casciide Iiangc* in the western portions of the great volcanic fields of California, Oregon, Washington, Idaho, and Montana.

Magmas containing a small amount of absorlied gases and va{)ors, or having such a high degree of liquidity as to allow the gases easily to escape, are not extruded by exi)losive erup- tions, but are quietly jjoui-ed out, forming in each case a laru couc around the orifice. Lic^uid magmas make lava cones with gentle slopes. Cones m;ide from viscous magmas have stee]> slopes. By the accumulated outflows of li(iuid niiigmas for many centuries, high mountains are built up. ]\Iauna Loa, on the Island of Hawaii, is an (»xample of such a mountain. Its slo])es are gentle, with a, base .it sea level 70 miles in width, and it rises to a height of aliout 14,000 feet above the sea. The amount of mat(>rial poured out at any one time may be large or small. The activitj' is always intermittent, with relatively long periods of quiet sejjarating short intervals of ei'Ui>tion.

As lava cones and cindei' cones are built u]i higher and

J42 • MOL'NT SHASTA, A IVriCAL VOLCANO.

liigher by successive eruptious, the passageway or chiimiey tliroiigli wliich the material comes up from the earth's interior is h^ugtheued, ami the magma lises within tlie chimney. The hydrostatic pressure of tlie cohimu increases as it rises, until it becomes sufficient to l>urst open the side of tlie cone, and the lava flows out on the lower slopes.

Volcanoes arc cinder cones, lava cones, or cones composed of both cinders and coulees. They are conical mountains made up wholly of volcanic material i)iled up around the vent from which it issued. Cinder con»»s and lava cones are common, but they are usiuilly less imi>osin.u; than the volcanoes made up of both cinders and coidet's, such as result from explosive and effusive erui)tions combined. From what is known of the distribution of volcanic material, it is probable that much more of it has reached the surface by effusive than l)y explosive eruptions.

MOrXT SHASTA.

Location. — Mount Shasta is in the middle portion of north- ern California, near the head waters of Sacramento Kiver, and belongs to the Cascade Range of mountains. It immediately adjoins the Klamath Mountains of the Coast Range, aud stands in line with the axis of the Sierra Nevada. In simple grandeur it rises high above its rugged neighbors as a mighty monarch among giants. The gi-eat altitude of its snow-capped summit makes it a conspicuous landmark over a large area, and has guided many a pioneer on his way to the Pacific coast. Mount Whitney rises higher above the sea than Mount Shasta; but as Mount Whitney is located among rival i>eaks, on an extensive elevated platform, its individual sui>remacy is not conspicuous. On the other hand, Mount Shasta stands alone at the head of Shasta Valley, and, although encom]iassed by high ridges and ])eaks, it still in-esents an imposing individuality. The traveler, in that region, when he oi)tains a general view, need not ask which is Shasta. The mouutaius in its neighborhood, though reaching over 2,500 feet higher than any of the Appalacliians, only serve to magnify the gi-andetir of Shasta, as its massive (^one towers a mile above them all.

Shape and Size. — Mount Shasta seen from the east, as shown in Fig. .3, is a simple cone. So far at least as shape is concerned, it is a tyjiieal exami)le of a large volcano, made up

COMPOSITION AND STKUCTURE.

24;{

of cinders and coulees which accumulated aliout the volcanic chimney from which they issued. No other type of mountain attains such a beautiful, graceful, yet simple and extensive stretch of slope risiiji;: into the sky. Tlie point of view in Fig. 3 is over a mile above the sea. The summit, in its summer garb, rises 8,450 feet above us, and attains an altitude of 14,350 feet. The upper 3,000 feet of the mountain, where cliflfs are most abundant.

FlQ. 3. — Mount Sliasta from the East.

has slopes averaging nearly 35 degrees. Farther down, the slopes gradually decrease in angle of inclination to 20 degrees, 15 de- grees, and 10 degrees ; and fiiiiilly, about tlie bas(^ of the mountaiit, the long, gentle sloi)e devdates but 5 degrees from a level i)laiu. From the sunmiit of IMount Shasta toward all points seen in the view, its flanks increase in length as they decrease in angle of inclination. Tlie slope of the mountain as a whole is a curve concave ui)ward, with the greatest curvature near the top.

The base of the mountain is 17 miles in diameter, and its height above the base is over 2 miles. Its volume is in the neighborhood of 84 cubic miles.

Composition and Stuuctuue. — The form of Mount Shasta is that of a typical volcano, and we might regard the form alone as

244 MOUNT SHASTA, A TYPICAL VOLCANO.

siiflScient evideuce to prove the voleauk- origin of the mountain. There are other facts which lead to the same conclusion.

Volcanoes art> composed of rocks which result from the cool- inj? and solidification of molten material erupted from the inte- rior of the earth. Jf the material cools slowly, crystals develop; and the amount of matter ciystallized is proportional to the length of time the slow cooling continues. In some cases the process is continued long enough for the whole mass to becom«> crystallized. (Tenerally, however, a portii)n of the material in lavas is not crystallized; i.e., it remains amori)hous, and some- times even glassy, because of the sud<lcn chill terminating the gradual cooling before crystallization is complete. The structure of lavas (made uj>, as they are, of either crystals or amorphous material, or both) is peculiar, and affords a means of distinguish- ing volcanic rocks from rocks which tn-iginate in other ways.

The rocks of Mount Shasta usually contain some well- developed crystals, l)ut a large portion of the mass is amori)hous. In all cases, however, their structure is that which is j)cculiar to lavas, and there can be no doubt as to the origin of the rocks.

1 1'.- 4. — .Muuiil .Siia.-Ia troui Iliv .\uitli.

COULEES. 245

The volcanic origin of Mount Shasta is iudicateil uot only by its form and composition, hut also l)y its structure. It is made up of irreguhu- layers of lava, altcrnatinfr here and there with others of fraixnieutal volcanic material. The layers overhij) one another somewhat lik(^ the shingles of a conical roof, and piodvice the structure which is chai'actei-istic of volcanoes.

CoNSTitrcTiONA]. Featikes. — Fi-om 1 he east, as seen in Fig. ;!, Mount Shasta appears to ])e a single cone, as if all the lavas of which it is composed luid escajici! iVom one vent. Seen from the north, as illustrated in Fig. 4, its doubh' strnctui-e api)ears. \/ There were two important vents about a mile and a half aj)art. The principal summit is on the left, 'i'hat on tlie I'ight is Slias- tinn, whose altitude is about 2,000 feet lower than the other. Its truncated form suggests a crater in the smmnit ; and this sug- gestion is vei'ihed by ascent, as shown in tlie map (j). L'-lCi). The crater-like rim is well preserved, except on the west, where it is broken away. On the slopes, especially towai-d the liase, are a nmnlier of smaller cones. Some are of cinders, and others of lava, but the most conuncui fonri of ad<lition in l)uilding uj) Mount Shasta was coulees without cones.

Coulees. — On the northwestern sjojie, at an altitude of from 5,000 to (),()()() feet, is Lava Park. Judging from the freshness of tlie lava, it is the youngest coulee of the mountain. The slope at that point is c(miparatively gentle, so that the lava sjtread broadly, and tlie coulei^ is nearly as wide as long. The greater portion of the park is without vegetation. It is an extremi'ly rough jtile of rocks, covei-ing an area of about two s(|uai(' miles, on which tliere is so little soil that arl)oreal vegetation has not yet obtained a hold. It ends on all sides aliruptly, like a terrace. The magma was viscous at the time of its extrusion, and l)roke into sharp, angular blocks as it was ])nshed along over the sur- face. The general character of this coulee is nuu-li like that shown in Fig. .5, which rej)resents a coulee on the little Snag Lake cinder cone, 5S miles southeast of Blount Shasta. This form of coulee is exce])ti<)iial on the slopes of ]\[(nuit Shasta.

A well-marked coulee occurs on the western slope. It inir.st forth at an elevation of 5,000 f(>et, and flowed northwestward in a rather narrow stream for several miles. 'IMie siii'face of this flow- is like that of Lava Park.

A com]»aratively recent coulee appears uii the southwestern slo{»e of the mountain. The trail u]) the mountain follows lliis

S«r*«T*4 frrUSCMtDfu) i*rr*t'*»*- E«CM<«iUaMcW T<«»(f««k«r

"«- re*d» ahoitt &<>»M>i farftukaJ bv C«Brf> N.Nch

MAP OF MOUNT SHASTA.

246

COULEES.

241

••oule. tor several ,n,Ies; ai.d the rou^^h, hackly, stea,n-t..rn sur- face of the ava is well exposed. It is timbered like the a<lioin- mg slopes, showing that the flow is older than ,Mtl,er of the other two mentione.1. Its surface has not been scored by the ancient

IffiMK ,%^> .'Trl'yfij

Flc. 5. — T)u" Surface of a ( ..ul,,-

li Snag Lake (inili-r ('(.n,-.

gliic.iers which once covered a large i)art, if not the whole, of the southwestern slope of the mountain. It is evident that its ex- trusion occuiTcd since the period of greatest glacial extension, the glacial period.

On the northeastern slope of the mountain, at an clcvjition of

X

248 MOUNT SHASTA, A TYPICAL VOLCANO.

nearly 10,000 feet, several well-marked coulees have their source. Their tabular fonn may be distiuguished iu Fig. o between the snow and the forest. The longest forms the flat divide be- tween the ui>i»er [lortious of iirewcr and Ineonstanee creeks, and courses down tlie mountain slope for t)ver four miles. Below, it widens out and rises higher and higher above the adjacent sur- face. The lower cud is abrupt, and forni« a prominent clili. The top is Hat from side to side, but the edges of the flow are steep. At the head oi' Brewer (^reek is a short tabular coule(> tenninat- ing below in a cliff, but the cliflf is uot so high as that which ter- minates the longer coidee. In gcnei'al, the newer flows, foiTuing the upper portion of the mountain, arc smaller than the older ones over which they were poured (mt. All end below in cliffs; so that, as one iisccnds the mountain, here and there he mounts as if on giant stairs, with long inclined steps (or treads) and steep risers, over the ends of the successively siiorter lava Hows.

The later Hows that Ijurst from the upper portion of the mountain were more viscous, and generally less copious, than those which issued from the base. The former built up the steep slopes, while the latter sjiread out the gentler slopes below, and occasionally formed extensive Hats, as shown in the fore- ground of Fig. 4. At the southeast base of the mountain, Elk Flats is underlined by a liasjiltic lav.-i, which at the time of its extrusion was much more liquid than most of the lavas of Mount Shasta. It doubtless contained large quantities of steam at the time of its ern])tion, for the lava is full of si'ijall cavities (liubbles), due to the expansion of the gases it originally contained.

The longest coulee from Mi>unt Shasta is one Avhich issued from the southern slope of the mountain at an elevation of about r),r)()0 feet, a little more thau a mile southwest of the Wagon Camj). The j)lentcons How of lava s]ircad from a cone on the crest of the ridge, sending one arm of llic lirojid roulee toward Panther Creek, and another toward the Sacramento. It com- ]>letcly surrounded Bear Butte, and forced Panther ("reek east- ward. It flowed between tlie hills of metamorphic rocks along Soda and S(|u,iw creeks. This branch of the great coulee ter- minated within a dozen miles of its source. The other arm of the How entered the canyon of Sacramento ]\iver, wliich it fol- low«'(l for nearly .lO miles. The magma was tliin. and it (hndit- less spread with considerable rapidity. Wherever the How was inqieded. bi'oad lake-like exiiansions of the stream weiv formed.

COULEES. 24!)

This occurred at miiiicroiis points aloiij:!^ tlie river, just ahove the narrow portions of the canyon. Tlie surfaces of the ponded tracts are smooth, and the interrupted drainage leads to the development of meadows. Tlie best example of this sort in the Shasta region is on S(iua\v' Creek, four miles Ix'low Nabar. In some regions meadows (h'velojK'd in this way are of much im- portance. This is esiiecially true in the Lassen Peak district, over 50 miles southeast of ]\Iount Shasta, wliere a large part of the agricultural land was tluis produced. \ Although a comparatively late flow, the extrusion of the coulee which followed down the Sacramento occurred many centuries ago. This we are able to roughly estimate from the fact that the river has not only removed nearly all of the lava from the canyon, l)ut has cut tht^ canyon moi-e than a hundred fe(!t deeper into the solid rocks than it was at the time the lava followed its course. At many points ahmg the river^ between r})per Soda Springs and the tunnel four miles below the Sacra- mento Kiver bridge, there are terraces of lava clinging to the sides of the canyon. These terraces are remnants of a once con- tinuous coulee that reached to a point .")() miles from its source.

None of the Shasta coulees already m(>ntioned have been glaviated. Tlu^ suifaces of the tlows retain their pristine rough- ness, and it is evident that tiiey have lieen (^xtruded sin<'e the glacial period.

The postglacial coulees form only a thin local vi-neer on the mountain slopes. Most of the erui)ted lava is older, and shows traces of glacial action. The great coulee which cour.ses down the southeastern slopi* of the mountain, and ends in a prominent ('lift' between Mud and Scpiaw creeks, is well glaciated. Its sur- face at many points is either rounded and striated, or covered by glacial moraines. IVFount Shasta was nearly as large during the glacial ])eiMod as it is now. Since that episode it has gained liut little more by addition of new lava flows than it has lost by degradation.

Near th(^ summit, on the southwestern slope of the mountain, is a coulee of exceptional charactei-. It is composed chiefly of lapilli, and forms tliR so-called re(l-and-l)lack rock with which the climber on th(> usual trail u]) Mount Shasta becomes familiar at an elevation of from i:!,(](>() to U,0(H) feet. The material is wholly fragmental, and is the result of the last eruption from tlie sunnnit of Shasta. The cinder-covered .slope of this coulee, over

1250 JRUNT SHASTA, A I VrRAl> VULCA.Nii.

wiiii-li the trail aiiinoarlics tlic siiiiiiiiit, lias the appearance oi a recent eruption, and it is pussilile thiit the last real volcaiiic aelivity al)i>ut Mount Shasta oecni'ied at this ]»)int.

A variety of surt'aee features of the lava tlows are illustrated by these coulees. The rough, angular blocks of Lava Park, the steam-torn, hackly surface of the trail flow, the ciiider-cov- ei-ed slope of the flow near the summit of the uiountain above ^IcCloud (Jlacier, aud the bubl)ly and ropy surface of the Elk Flat coulee, are good examples of the various types of lava sur- face. At the last-named locality the suiface is in ]tlaces covered with low domes, as if there were great Imbliles beneath. This featui-e is better illustrated by one of the <>ld(>r lavas near Ash Creek, at an e]e\'ation of between (i,0()() and .'-!,()()0 feet, where they have various forms rising sometimes to a height of 1:2 f(»et, with a diameter of l-t feet, and usually with well-marked radial jointing. The protuberan<'e from the upper surface of the lava flow sometimes rises so high that it bends over, as if about to fall from its own weight.

On the southwestern slope of ^lud (.'reek Canyon, below the Upper Falls, is a prominent glaciated clitt" 75 feet in height. It is Ijeautifully liauded with gray and red. The bands vary from a small fra<-tion of an inch to a foot in thickness, and aredoul)t- less piimary, originating at the time the lava was erui>te<l.

Cones. — The pressure of the magma within the jjrincipal vent burst open the side of the mountain. (Jeneraliy the molten material flowed out in a gentle stream, Imt ()c<*asionally it rose fcmntain-like, and resulted in the fcjrniatioii of a ];iva cone. On the northeastern slope of the mountain, near tlie lower edge of the snow, is a hill composed wholly of lava. Its form, as seen in tlie(listant view, suggests that it is a lava cone directly over the vent from which f\\o lava issued.

On the southern slope, as shown on the map (\k -4()), ranging from 8,000 feet down to nearly 4,000 feet, is a series of five cones arranged in a curved line gently convex to the westward. All these hills are lava cones except the one at an elevation of 6,800 feet. Beai' i^>ntte is a fine example of a lava cone, and its foiTn leads us to expect to find a crater in its snnnnit. This expecta- tion, however, is not well founded. The most conspicuous eleva- tioTi of this kind about Mount .Shasta is Cone Mountain, near the railroad at the western base. It rises over 1?,000 feet above the surrounding country, ami its slopes are indim-d at an angle of

CONES. 1251

al)out .'!.") (lefijrees. Cone Muuutaiu \v;is iiaiiit'd l)y Prol'essor Wliitiiey ill 18G5 on account of its fonu. Altlioi]fi:h its steep slopes are formed chiefly of angular fragments, they are not I'iiiders, lapilli, bombs, or blocks, such as result from exi)losive erui)tioii. The solid lava since its extrusion, or perhaps in jjart at that time, was broken to pieces. There is no trace of a crater in its summit, nor of ejected fragmeiital material on its flanks, to indicate that the formation of the cone was to any degree due to explosive action. At the time of its extrusion the lava must have been very viscous to l)uild up such a sharp cone. Had it been as liquid as that of Elk Flat, it would have spread out so as to form a plain, instead of a prominent mountain several tiiousand feet in height.

Of the cinder cones there are about lialf a dozen f)ii the slo))es of Mount Shasta; l)ut they are, as a ride, less consjiicuous than the lava cones. Their location may be seen on the map in cases where they are sufficiently elevated to lie marked by one or more contours. On the western slojje of Lava Park is a (binder cone over 200 feet high, with a well-preserved crater in its summit. Black Butte, northeast of IMount Shasta, has a double crater, with a very low rim of cinders. Those ejet^ted from the crater are dark, and consist of tiie same sort of lava as tliat of wliicii tiie most of Black Butte is composed. It is especially interest- ing to find s(uittered over the rim, and witliin tliis crater, frag- ments of pumice like that ejected by the last erujition from tiie summit of Mount Shasta. It indicates clearly that Shasta lias been in eru])tion since the twin crater of Black Butte was formed.

Black Butte can scarcely be considered a part of Mount Sliasta, althougli its lavas, as well as those of Ash Creek liutte, have contributed to the u]ibuildingof the mountain's base. Ash ('reek Butte is a cone containing both lavas and cinders; and, judging from the amoi;nt of (>rosion it has sutt'ered, it is of greater age than the other cones al)out jNlount Shasta.

One of the most interc^sting cinder cones on the sloi)es of Mount Shasta is between the two branches of Panther Creek, at an elevation of (J,rtO() feet. It is a low, rounded dome, composed of red lapilli, and is sometimes called Red Hill. The summit has a regular convex curve, without the slightest sugg(>stion of a crater to mark tlie liole from which the material was blown out. Lava has escajjcd from its liase on both sidi^s, and two short coulees course down the adjacent ravines.

•?n>

MOUNT SHASTA, A TYPICAL VOLCANO.

The origin of such dome-shaped, cvaterless oiuder eoues is a ijiatter of doubt ; l)Ut a suggestion that they are due to glaeial action on an ordinary cinder cone is found in the fact tliat tliis hill, instead of being exactly conical, is elli]>tical, with its longest axis parallel to the slope of the mountain. This \-iew is strength- ened l>y observations on a sinulai' cone on tlie slope of Mount Shasta, about a mile northwest from the road at the summit in the pass between Mount Shasta and Black Butte. The uus>nn- metrical elliptical hill at this plaee is about KM) feet high, with one slope of 4t) degrees and the other t)nly 20 degrees. The top is irregular, dome-shaped, without a trace of a <lepression or crater to mark the point of ejection. On the sunnnit are a number of large bowlders of lava, <liffering from that of Avhich the hill is composed. They must have been carried there, and the most probable agent of transportation is glacial ice. The effect of glacial erosion on a cinder cone over which it passes, if not too h»ng continued, so as to remove the cone entirely, would be to oliliterate the crater, and make a more or less elli]»tical hill, with its longest axis parallel to glacial motion. The two elliptical cinder cones referred to are preglacial: while the others, liaving well-preserved craters, are postglacial.

Southwest of Wagon Camp is the cinder cone from wliose base escaped the great coulee that extends down tlie S.-icramento Canyon for 50 nules. It is nearly (iOO feet high, with well-detined crater, suiTounded by a rim of cinders. This is one of the most accessible cinder cones on the mountain.

Although the great body of Mount Shasta is made up of coulees of lava, it still contains a large proportion of fragmental material, and must be considered a mixed cone. On the north side of the canyon of Mud Creek, at an elevation of from 8,000 to !),000 feet, and also bek)w the timber line in both walls of the canyon, there are fine exposm-es of fragmental material ejected from the jn'incipal crater. With the exception of the cinder coulee already noted, this is the most important exposure of fragmental material ejected from the main vent.

Mount Shasta is a doul)le cone. The two are so closely joined as to make but one cone Ijelow an altittuh^ of 10,000 feet. AI)ove this k^ve! the two cones may be distinguished. They mark the ininci]>al vents from wliicli Imrst forth the coulees to l)uild uj) the great mass of the mounti)in. All the other cones on the slopes of tlie jirincipal one, whether composed of lava or

VARIETIES OF LAVA. 253

cinders, are subordinate, aud make the position of subsidiary vents. Besides the two i)rineipal vents, there are traces of more than a score of subsidiaiy ones which contributed to the upltuild- ing of the mass. Many others may be found covered up in the gTowth of the mountain Ijy the coulees coming down from the principal vents.

Vakieties of Lava. — Rocks resulting from the solidification of molten material brought from the earth's interior by volcanic action are volcanic I'ocks. There arc; many varieties of volcanic rocks, arising fnjni ditt'erences in structure and composition. Only three need Ije mentioned here. They are rhi/nHtc, andesile, and basalt, and their distinction is based largely on chemical and mineralogic composition. Khyolites contain in general some- where l)etween 66 and 80 per cent of silica; andesites, lietweeii 55 and &y per cent; and basalts, between 45 and 55 pei- cent. Silica in a pure state is illustrated by the mineral (piartz. It is a substance Avliich is fused with great ditticully; and we may at once infer that rhyolites, being more siliceous than andesites and basalts, are less fusible. On this acccmnt rhyolites at the time of their eruption are generally much more viscous aud stiff than basalts. The magmas of many basalts when erupted are almost as licpiid as water. They spread far and wide in thin sheets, with even, level surface, like the water of a lake. The degree of li(piidity of a magma at the time of its eru2)tion deter- mines the shape of the physiograi)hic feature to which it gives ri.se.

The lavas of Mount Shasta are andesites and basalts. Al- though intermingled on the same slope, they are of more or less distinct eru^jtion, and associated in certain cases with special topograi)hical features. The most ancient variety of lava about Mount Shasta is one contaijiing prominent crystals of black hornblende. The genei-al color of the rock is light gray, and, on account of the conspicuous crystals of hornblende it contains, it is called hoi-nblende andesite. It is <'xeniplified in Cone Mountain. At tli<' time of its ei-ui)tion the magma was evidently quite viscous, so as to maintain stee]) slo])es. On expo.smv to the weather it sometimes becomes reddish. It forms a large tract of the westcM'u slope of Shastina, and is exposed also near the foot of MeOloud Glacier and other localities on the eastern and northern slopes.

The most abundant lava of Mount Shasta is liy])erstliene andesite, — a lava containing little or no hornblende, Init much

254 MOUNT SHASTA, A TYPICAL VOLCANO.

hypersthene. It rauges in color t'loiu light and dark gray, often reddish, to black. This entire range of color may be seen on ascending the trail uji the southwestern slo^^e of the mountain. The trail is on hj'persthene andesite all the way. In the later stages of growth, hyi>erstheue andesite has contributed nuich more than hornblende andesite to tlic upbuilding of the mountain.

The third variety, basalt, is found only on the lower slopes of the mountain, forming nearly all of the cinder cones and the plains. In the cinder cones the lapilli of basalt are often deeply colored, red, yellow, or black. On the plains the basalt is gener- ally gray, but sometimes verges upon black. It was xisually more liquid at the time of its eruption than t'ither of the andesites, and spread out, foi-niing comparatively smooth surfaces, as at Elk Flat and the northern foot of Mount Shasta, west of Sheep Rock. If all the lavas that now appear on Mount Shasta had been as liquid as that of Elk Flat, the form of Mount Shasta would have been very different from that which it now has. Of this w(» can get a clearer idea by comiiariug ]\Iount Shasta with Mauna Loa. Mauna Loa is 14,000 feet in height. Its lavas have such a high degree of liquidity, and retain their mobility so long after eruption, that the base of the mountain spread by them has a diameter of about 70 miles and an average slope of ."> degrees. The base of Mount Shasta is less than "JO miles in diameter, and its average slope nearly 15 degi'ees. Eighteen hundred feet below the summit of ^Mauna Loa its diameter eqi;als that of the base of Mount Shasta, while the diameter of the latter in a (torrespond- ing jiosition is less than 2 miles. The unlike form of the two mountains is attributable chiefly to a difference in the degree of li(inidity of the lavas of which they were constructed.

Lava Caves. — In the gentle lava .slopes about two miles southwest of Sheep Rock is Plutos Cave. It is shaped like a railroad tunnel. The l)ottom is generally flat, and covered by debris fallen from the sides an<l roof. In places the cave is nearly filled with such material. The walls ha\'e a sheUy struc- ture, and generally form a beautiful arch across the cave. An oi)ening to the surface, affording an entrance to the subteiranean passage, resulted from the falling-in of the roof. The cave, where best developed, is from GO to 80 feet in height, and from 20 to 70 feet in width. It has been followed for nearly a mile without finding its terjnination, and it may l)e considerably longer. The crust or roof of the tunnel ranges from 10 to 75

MKTEOKOLCXiUAl. ( (IXIHTIONS. 25.')

feet iu thickness, and the lava of whieii it is composed is full of cavities fonueil by the expaiidiug steam in the lava at the time of its eruption. Many of these cavities are elongated parallel to the tunnel ; that is, in the direction of the flow of the lava.

The sides and roof of the tunnel have caved in, so that the original lining of the cave has generally disappeared; but rem- nants here and tliere show that its surface was spongy, or niai-ked by narrow, puckering folds. It is evident that tlie cave resulted from the escape of the molten inleiior of a coulee. The crust formed; but, before the whole mass was solid, the liquid escaped farther down the slo2)e, and flowed out, leaving a cavity within the coulee's crust. The tunnel is liued here and there by blisters and froth-like exudations of lava from the sides; but no distinct stala(^tites and stcilagmites of lava, such as Professor Dana re- ported from tlie lava tunnels (m the slojies of Mauna I>oa, were seen in Plutos Cave.

The surface of the coiuitiy about IMutos Cave is flat, but rough, with iri'egular domes and blisters of lava. Judging from the hollow sound one hears in walking or riding over many por- tions of the lava about the base of Mount Shasta, it is probable that there are numerous caves in that ivgion. 8uch caverns are known to exist not oidy at the northwestern l)ase, but also at the southeastern, in the neighborhood of Elk Flat. This feature of vulcanism is especially well displayed in the so-called lava l)eds .")() miles northeast of ]\Ionnt Shasta, where the Indians undei- (.'aptaiu Jack so long successlully defied our troojis. i\Iany of file tunnels hav(* caved in, leaving the country fi-aversed liy dee]i, rocky canals, such as to render it almost imj)assable at right angles to the flows. During the winter, snow drifts into the canals, and forms sulKcieut accumulation of ice in some cases to last all summer, furnishing a scanty supjily of wat(M" in a region wliere it is otherwise scarce.

Meteoiiologic.vl Coxditions. — In strong couti-ast with the ^cii'cumstances attending the upbuilding of Mount Shasta when it was an active volcano, belching fortii streams of fiery lava, are its arctic conditious of to-day, with its summit wrappe<l iu eternal snow. It has long been the field whereon was fought the ])attle l)etween the elements within the earth and those above it. In the early days the forces beneath were victorious, an<l built up the mountain in the face of wind and weather; but gradually the volcanic energy reached its climax, declined, and jiassed away.

'2i)(i MOUNT SHASTA, A lYl'ICAL VOLCANO.

Tlie loss of lu'iit was succeoiled by icy cold, wliicli oiifiicd i In- way to more vigorous, unrcpcllcd attack of those destructive aj-'eucies tluit are now reversing the jirocess, and slowly hut surely wear- ing the mountain away, and reducing it toward a general level.

On the slopes of Mount Shasta, between its base and its sum- nut, there is a wide range in meteorological conditions, deter- mined by <litferences of altitude, thus dividing the mountain into climatic zones. On tlie middle slope is the great forest belt; above it, encii'cling the top, is the cold, moist zone; and at the very lowest points of the base of the moiuitain, in Shasta \'alley and Elk Flat, there is a warmer, dry zone.

The lower, middle, and upper zones dilfer widely not only iu temperature, i)recipitati(>n, and vegetation, but also in tli(»ir slopes and consequent gradational featui-es.

Lower Zone. — The influence of temperature on precipitation, and the limits which it tlirows al)out arboreal vegetation, are liere most forcibly illustrated. This zone is not continuous about the mountain. It is fully developed only at the northwestern and southeastern bases of the mountain in Shasta Valley and Elk Flat. In Shasta Valley, at an elevation of about 3,000 feet above the sea, where the average temperatur(> is high as com- pared with that upon the mountain itself, tlie precipitation is always in the fonn of rain, but not sufficient in quantity, espe- cially on account of its unequal distribution througlioitt the year, to support more than a scanty growth of stunted trees. In the autumn, storm clouds gather al)out the smnmit, and showers become frecjuent, spreading over the hmd in copious I'ains. Jie- fore the spring, eight ninths of all the annual rain has fallen, and the country is brilliant with living green. As summer ad- vances, the refreshing showers disappear, and the clottdless sky affords no protection from the burning sun ; the bright green fades away, and the earth gi-adually assumes that imiuviting, seared aspect which pervades all nature in the season of droitght.

Middle Zone. — On the middle slojies of tiie moiuitain, by the cooling influence of altittide, the rainfall is gradually increased, and th(» vegetation is luxuriant. From the limits of this zone, arboreal vegetation gradually diminishes in stature and number toward the upper and lower zones. The trees are almost wliolly coniferous. Among nearly a score of species the sugar pine is monarch, frequently attaining a diameter of 12 feet and a height of over 200 feet. Farther up the mountain these gradually give

METROKOLOdlCAL CONDITIOXS. J'j^

■wiiy to firs, wliosf tall, f;ra('i't'iil tonus live in pcrfeot kopjiinji w itli the iiiaj<^stii' iiioiuitaiii hchiiid tln'iii. Their black-aud-yellow s])(itt<'il trunks and l)raiR'hos, drapcil lierf and there in loug jx'udent moss, pi't-scut a wcii'd, almosl dismal aspect, makinfi a tit promenade for the mythieal deities supposed by theaborigiues to inhabit the mountain. To assume that in tlie timber belt the slopes of th(» mountains are everywhere covered with majestic trees would certainly be wide of the trath, for within the forests are large treeless tracts sometinjes luuidreds of acres in extent. From a distance these gi-een, velvety acres appear to be very in- viting i»astures, and present the most desirable path of ascent. A closer examination, however, discovers to the ob.server, that, iustead of grass, these green fields are clothed in such a dense shrubbery of manzanita, Ceiuiotlius, and othei' bushy plants, as to be almost impas.sable. One attempt to cross a i>atch of chaparral, oi- "devil's acre," as it is sometimes ap]iropriately called in Western vernacular, will convince tin' traveler that his best path lies in the forest.

Uppi'v Zone. — The timber gradually diminishes in .stature as it ascends the mountain from an altitude of 7,000 feet to the re- gion where the precijiitation is generally, if not always, in a solid form, — snow in winter, and sleet in .summer. On the southwest- ern slope the forests cease abruptly at au elevation of about 8,000 feet, but upon the opposite slope they diminisli gradually to the i-egion covered by glaciers. The tree which climbs highest is Fh/Ufi ulhkunlis. Its stem becomes shorter and the top flattens as one ascends. ,\t an elevation of about 9,000 feet the branches are spread on the ground, so that not infrequently the pedestrian finds his best path over the tree tops. Beyond these, on the suowless slopes, are found only scattered blades of grass, and the welcome little Iliilsra, the edelweiss of our Al])ine regions, witli its bright flowers to alleviate the arctic desolation of the place. The red and yellow lichens cling to the rocks, and the tiny Protococciis flourishes in the snow; .so that one is occasionally surprised, on looking hack, to see his "bloody" footjjrinfs.

In the Alps, between the zone of forests and the snow, are often found exten.sive pastures, where the herds which furnish milk for the celebrated Swiss cheese graze during the milder .seasons of the year. In northern California sinular pastures do not occur about the snow-capped summits, probably on account of the unequal distribution of the annual rainfall.

GLACIERS. 255)

(jtLACIEKs. — (Treat interest uttucliess to the j^laciers of the upper portiou of Mouut 81ia.sta. There are live in number, and all are found side by side, fonuing an almost continuous covei*- ing for that portion of the mountain at an altitude of about 10,000 feet. On the northwestern slope of the mountain is Whit- ney Glacier, with its j^rominent terminal moraine; to the east- ward is Bulam Glaciei', with a large pile of debris at its lower end ; next comes the broad Hotlum Glacier, and then the Wintun. McOloud Glaciei-, which is the smallest of the group, lies on the southeastern side of the mountain.

Whitney GUk'u'i . — Wliitney GUicier is more like those of the Alps than any other om^ of the group. Its snow field lies on the northwestern slope of the mountain, from whence the icy mass, with well-defined limits, moves down a shallow depression be- tween Shasta and Shastina. Its width varies from 1,000 to 1^,000 feet, with a length of about 2,;^ miles, reaching from the summit of the mountain down to an altitude of 9,500 feet abo.ve the sea. It is but little more than a decade since the first glaciers were discovered within the riiited States; and the hirgest of th(^m, about the culminating point of the Cascade Range, would jjcrluips a])pear Lillii>utian besidi' the great glaciei' of the Bernese Oberland ; and yet they are as truly glaciers. In the upper portion of its coiu'se, passing over prominent irregu- larities in its bed, the Whitney Glacier becomes deei)ly fractured, producing the extremely jagged surface corresponding to ice falls of the Alpine glaciers. Lowei- down the crevasses develop, as shown in Fig. 6; and these, with the great fissure which separates the glacier from the steep slopes of Sliastina, attest the motion of the icy mass. They freciuently oi)en and become yawning chasms, reaching 100 feet into the clear green ice be- neath. N(^ar its middle, on the eastern margin, Wliitney (xlai^ier receives contributions of sand, gravel, and bowlders from the j vertical clift's around which it turns to move in a more northerly direction. In this way a prominent lateral moraine is developed. From the very steep slopes of Shastina, on the western side, the glacier i-ec^eives additions in the form of avalanches. Here the snow clings to the rocky b(^d until the strain resulting from its accumulation is great enough to lireak it from its moorings, and it rushes down upon the glacier below. The most striking fea- ture of Whitney Glacier, and that which is of the greatest interest from a geologic point of view, is the debris (moraine) it brings

2()0

MOUNT SHASTA, A TVPKAI. VOLCANO.

(lowu tlio inouiitaiii and piles up, making:; a largo aci-umulutioii (terminal moraine) at its lower end. This moraine (seen in Fig. 7) jippears to be fully a mile in length, measured down the slope of the mountain. Its apparent lengtli is much greater than the real, however, from the fact that the glaeier ice extends far beneath the covering of detritus. It is so huge a pile of light-colored debris, just above the timlier line, that it is ))lainly visible from

— Muunt Sliast:i from the Nortli.

afai'. The view aliove (Fig. 7) shows clearly the double character of tlie mountain, — Shastina on the right, and Shasta on the left, with the Whitney Glacier between them.

In comparing tlie morainal material about jNfount Shasta with that of the Alpine glaciers, a feature that is particularly noticeable is the smallness of the bowlders. On Alpine glaciers bowlders frequently have a diameter greater than 10 feet, Itut about the Whitney and other glaciers of Mount Shasta they are rarely so much as ;> fe'et in diameter. Tins is readily ex]ilaiiied by the fact that the glaciers of Mount Shasta do not move in deep valleys, bounded by long, steep slopes, with many high cliffs, affording an o])])ortunity for the formation of large bowl- ders. Although Wliitni'v (Tlaciei- has its boundai-ies more clearh'

OLACIEKb. 261

(It'fiiK^d than any of tla- other g-laciers about .Mount Shasta l.y th(i depression in wliich it moves, tlie valley is veiy shallow, and one looks in vain along its slope for tra<,'es of polished rocks like those so magnificently dis])layed in the Alpine valleys. Whitney (Jlacier looks young: it has hardly made a heginning toward carving out a valley for itself.

Below the terminal moraine the milky water of Whitney Creek wends its way down the northern slope, y>hinges over a fall hundreds of feet high into a deep canyon, and near tlu,' base of the mountain is consumed by the thirsty air and earth.

The pi-esence of marginal crevasses, lateral and tei-minal moraines, and the <-liaracteiistic milky stream which issues from the lower end, are proofs that Whitney Glacier moves, but the rate of motion has not been definitely measured. The stakes planted in July, 1884, were covei-ed with snow ])eforo the party could rea(?h them in October, and thej^ have since disappeai-ed.

liitlant (T/ncicr. — On tlie northwestern slope of the mountain, to the left of Whitney Glaci(M-, as seen in Fig. 7, is the Bulam, dift'eriug cliiefiy in that it is contained in a broachM', less definite valley, and forming an intermediate step toward Hotlum Glacier, which is one of the most imjiortant and i-emai'kable of the grouj).

Hotlitiii Glacier. — Unlike the ordinary glaciers, Hotlum has no valley in which it is confined, but lies on the convex siuface of the mountain. Its u])p('r surface is convex throughout from side to side, and its width {l."J;> miles) is almost as great as its length {l.()2 miles). At several places the surface of the glaciei- is ma(h' very rough by the ine(iualities of its bed. This is especially trvie of the southern ]>ortion, where ])r(miinent dijfs furnish material for the only medial moraine discovered on Mount Shasta. Throughout the greater portion of its expanse tlie glacier is deeply crevassed, exjiosing the green ice occasion- ally to the dei)th of 10(1 feet. The thickness of this glacier has been overestimated. In reality, instead of being 1,800 to 2,r)00 feet thick, it does not api)ear where greatest to be more than a few hundi-ed feet, for at a nund»er of places it is so thin that its bed is exposed. Its terminal moraine is a huge j)ile neai'ly half a mile in width measured in the direction of glacial motion, and twice as long measured along the end of the glacier.

Whifnii (rlucicr. — Next south of llotlum (Jlacier is Wintun, which attains a length of over two miles, and ends with an nbrupt front of ice in a canyon. In this respect it is strongly

'2&2 MOUNT SHASTA, A TYPICAL VOLCANO.

contrasted with tho utlier glaciers of Mornit Shasta. There is uo well-marked terminal nu)raiue, although there are accumula- tions of del)ris on the northern side ne:ir the end. The detritus is ai>pavently swept out of the eanyou l)y Ash Creek as fast as it is brought there l>y the glacier, aud thus tlie accunuilation of a terminal moraine is ]irevente(l.

McCloiul Gluciri. — On the southeastern slope of Mount Sliasta, at the head of a large canyou, is the McCloud Glacier. It adjoins the Wiutun, aud is the smallest glacier of the group. Notwithstanding its diminutive size, its crevasses and the muddy stream it initiates indicate clearly that the ice mass coutinues to move. The amount of moraiual material upou its borders is small, and yet, of all the glaciers ahout Mount Shasta, it is the oidy oue which has left a promiueut record of iuiportant changes. The country adjacent to the southwestern side of ]Mud Creek Canyon has been distinctly glaciated, so as to leave no doubt that McCloud Glacier was once very much larger than it is at the present time. The rocks over which it moved were deeply striated, and so abraded as to produce the smooth, rounded sur- face so common in glaciated regions. At the time of its greatest extension the ghicier was over 5 miles iu length, and occupied an area of at least 7 sciuare miles, being twenty times its present size. Its limit is outlined at several ])laces by i>rominent terminal moraines, which mark stages in the recession of the glacier. The thic^kness of the glacier, where greatest, was proba- bly not more than "JOO feet ; for several hills within the glaciated area were not covei-ed, and the striated surfaces and moraines do not extend u]> their slopes more than 200 feet. The thickness of the glacier is completely in harmony with the limited extent of its erosion. Althoiigh the rocks are distinctly i)laned off, so that the low knobs and edges have regularly curved outlines, it is esideut that a great thickness has not been removed by the ice, and that the period of ice erosion has been comparatively brief. Dui-ing the lapse of time, however, there have been climatic oscillations, embracing epochs of glacial advance and recession.

With the exception of ]\IcCloud Glacier, there are no records upon the slopes of Shasta that any of the existing glaciers were ever very much larger than at present.

At the southwestern foot of the mountain, near the railroad, there is a large ai'ea covered by gla<-ial moraine in the form of rounded and irregular hills, inclosing many small basins, above

SPRINGS. 263

which they rise rarelj- as iiiu<'ii as oO feet. This moraiue is composed of the older lavas of that portiou of Mount Shasta, and demonstrates that during the glacial i)eriod the southwest- ern slope of the mountain had an iee stream 10 miles in length, '{'he glaciers on the othei- portions of the mountain must then have been much larger thau uow, and it is prol)able that their records havt^ to a large extent hccTi buried Iteneath later eruptions.

Si'iiiN(;s. — -Made up, as it is, of iml)ricated coulees and f rag- mental material, all of which is more or less porous and full of fissures. Mount Shasta absorbs the principal jioi'tion of the precipitation on its slopes. The rainfall on Mount Shasta is large. The amount of water that reaches McCloud, Sacramento, and Shasta rivers by surface drainage is very small. By far the greater portion of the drainage of Mount Shasta is subterranc^an. This is shown by tht^ large springs aljout its base.

The Big Spring, above Sissous, is a fine example, giving rise to a good-sized stream, that by sonu* has l)een considered the head of the Sacramento. Moss Brae Falls are produced by springs issuing from between the coulees of Mount Shasta on the side of the i^anyon of the Sacramento, and cascading ovei- tlie grassy slope to the river below.

The greatest springs are those in McCloud Canyon, where the river cuts the southern edge of the lavas from Shasta on the border of Elk Flat. Large volumes of water issue from the river bank, and the size of the sti'eam is (loid)led by their addition.

Scpiaw Creek originates in springs. The flow is copious, regular, and clear as crystal. It is a b(>autiful, transj)arent, limpid stream, strongly contrasted with its nuiildy neighl)or <'oming down from McCloud Glacier.

Th(^ greatest springs are low down the mountain sIojm', al- though there are many smaller ones above.

On the summit of the mountain there is a small group of openings from which hot sulphurous gases are continuously es- caping. The place is sometimes referred to as the Hot Spring, but, as gases only escajie, it is Tuore propei'ly called a sol/atani. The earth about the holes is warm, but, as the \'apoi's are noxious, the pla<'e cannot b(> used as a source of heat for the camper who may wish to remain on the cold summit over night. Down the northern slope, between AVhitney and Bulam glaciers, several hundred feet below the summit, is another solfatara. These are the last palpable vestiges of heat upon the mountain.

21)4 MtUNT SHASTA, A TVI'ICAI. VoLCAXO.

Stkeams. — A <i:laiii'e at the ma)) (\<. -M')) reveals a marked inegulavity iu the distvibutiou of streams on the slopes of Mount Shasta. They are nearly all on the eastern half of the mountain, and assoeiated directly witli the ,a;laciers. The reason for this distribution is found in the iirevailinn- soutlnvesterly winds of the region. These are so strong a)id enduring that the hrauehes of the exposed trees high up on the slopes ai'e l)lo\vn around to the northeastern side. It is only where wiuds continue to blow- steadily for a long time in one direction that such effects can be produced. The winter storms Avliich furnish the Shasta snow are driven by such winds, and the snow tin<ls a resting place only on the lee side of the mountain, and there the glaciers are formed.

Though all the streams depend for tlieir water suiijily upon the snow of the summit, some get it indirectly through springs, while others flow directly from the glaciers. Squaw Creek has its source in springs, while Miid Creek originates in McCloud Glacier. Each stream is a good example of its kind. They are close together, and yet strongly contrasted iu appearance. Squaw Creek is a beautiful, clear, refreshing stream, Avith in- viting banks; while Mud Ci-eek, as its name implies, is full of sediment, and its lianks are lined witli gravel, sand, and mud. The soiu'ce of the detritus is the glacier, which, as it gradually moves down the mountain slope, armed with many rock frag- ments, files ott' the surface, and jjroduces the mud, sand, and gravel for the stream to carry away. Glacier streams vary greatly in vohime, not only with the season, but also with the time of day. I)i;ring the winter there is little melting of snow and ice, and the streams have little water ; l)ut during the heated summer the supply is copious and floods prevail. For the same reason, also, the stream varies between day and night. Thus the returning sxui awakens the sleepy sti'eam, and sends the thrill of life into the mountain's circulation.

Most of the glacier streams sink on I'eaching the lower slope of the mountain. As the water supply declines, the point at which the stream disappears in its bed retreats farther up the slope, to return again with the diurnal pulsation of another sun. In the long streams there may he several ])ulsations at the same time. The hours of advance and retreat of the stream are deter- mined chiefly by the grade, and by distance from the glacier.

Falls. — Tt is readily understood that the abrujit termination of the coulees below leads to the development of faUs in the

DEGRADATIONAL FEATUEES. 265

.streiuus which find tlieir wiiy down the mountain slope. All tlie .streams of considerable size have such falls, and in the same stream sevei-al may occur. Mud Creek has three, — one within the forest Ijelt, auotlier near the timber line, and a third more tliau a mile farther up the stream. Ash Creek Fall, near the timl)er line, has a height of nearly 400 feet, and the stream plunges into a deep canyon. It is one of the most imi)ressive falls of the mountain. Bulam Creek and Whitney Creek have similar falls of great height; l)ut the streams are small, and on this iicconnt they are less imitressive than those of Ash Cre<'k.

DE(ii!Ai)ATi()NAL Featuues. — \\V huve consideJ-ed thost; feii- tures which oi-iginate in the upbuilding of the mountain, the meteorological circiimst.inces to which it gave birth, the forests, glaciers, streams, and falls that followed. Let us now turn our attention to the degradational featui'es developed by these con- ditions. The three zones into which the mountain slope is divided by its meteorological conditions an\ well marked by the consec^uent degradational featui'es. Instead, however, of desig- nating these zones according to elevation, they may in this case be named, from the characterizing featmv, tlie "Plain Zone," the "Canyon Zone," and the "Cirque Zone" respectively.

Plain Zone. — In this zone fuUy developed plains predominate, and there is but little erosion. Most of the sti-eams coming down from above the timber line sink when they reach the plain about the base of the mountain, and tlie drainage becomes subterranean. Dotted stream lines on the map indic^ate that the stream beds are usually dry. Whitney Creek, Inconstance (^i-eek. Brewer Creek, Ash Creek, and many smaller streams disappear from the sur- face during a large part of the year. All streams are enfeebled by subterranean leakage by the time they reach the Plain Zonc^, and the gentle slopes leave them little power of corrasion.

The banks of the glacier streams are lined with gravel, sand, and mud brought down from above. During the hot season, when the floods come; from the melting snows of the upper zone, the streams swell far beyond their winter limits, and carry away the accunudated debris. The low grade permits the streams to do l)ut litth? mor(^ than this. The degradation of the mouTitain's base is very slow. The streams flow in beds near the general level, and degradational features are not conspicuous.

Canjion Zone. — The Plain Zone passes rather abruptly up- ward into the Canyon Zone, with which it is in markcul contrast.

2(3(5 MOUNT SHASTA, A TYPICAL VOLCANO.

The Canyon Zone is in tlie forest belt. The protective covering- of Uviug and fallen leaves breaks the dash of the raiu. The roots bind the soil together, and the shade regulates the suddt'n changes and witle range of temperatm-e. Thus the forest pro- tects the slope on which it grows, and tends to prevent rapid degradation. This difference, however,* does not modify to any considerable extent the corrasion of the tumultuous streanjs fi-om the glaciers. Hea^aly armed with gravel and sand, tliey act upon their narrow beds somewliat as a file, continu- ally moving down the slope, and cut deep canyons across the forest belt.

The canyon of Mud Creek is the largest. It has a length of al)out 5 miles, and a depth where best developed of about 1,000 feet. At the tindjei' line it is not so deep, its slopes are less precipitous, and the canyon is crossed by n rude trail. Else- where it is almost impassable for horses. The middle falls of Mud Creek are near the timber line. Above this point the south- west wall of the canyon is made up largely of solid coulees, while the opposite side is comjjosed chiefly of fragmental material, on whose slopes is developed the pinnacled tojiograi)hy to which such formations frequently give rise. The canyon is deepest a mile l)elow the timber line. Its sides have a slope of about 'M degrees, with occasional columnar cliffs of tufa, reaching in some cases a heiglit of 50 feet. The I'ocks in which this portion of the canyon is carved are almost wholly fraginciital. It is treacherous climbing ground, for the rocks arc fragile, and afford unreliable support. They are more or less distinctly but imperfectly strati- fied, and dij) away from the moitntain at an angle of fi'om 8 to 12 degrees. The slope of the mountain is approximately ]iarallel to that of the layers of fragmental material, and suggests that the inclination of the layers was determined by that of the slope on which they were deposited, (^oulees of lava, where observed, are parallel to the siim(> slope, and it is apj)arent tlint some of the flows followed earlier canyons down the mountain sk)i)e. The three falls in this canyon are all over solid coulees.

The canyon of Ash (~^reek is neither so long nor so deep as that of Mud Creek, but is cut in harder rocks. It ends above at the falls, where the stream plunges over a mass of lava nearly 400 feet in thickness. The canyon walls are of the same mate- rial near the falls; Init beyond, the cotilees are less distinct, and fragmental mateiial increases. Two miles below the falls a

DEGKADATIONAX FEATURES. 2()7

stratum of pumiee "JO feet thick may be seen lying between somewhat thicker beds of saud and bowlders. The slopes, al- tliough steej), aiv generally wooded, and landslides are less fre- quent than in Mud Creek Canyon. ^Striated i-ocks in .situ oceur near the bottom of the canyon, over two miles below the present terminus of Wintun Glacier.

Brewer and luccmstance creeks are small, and their canyons are of corresponding size. On the other hand, Bulam and Wiiil- ney creeks are laiger, and have carved canyons, in some ])laees 000 feet deep, down the northern slojie of the mountain.

Cirque Zone — The Canyon Zone extends up the sloj)e of Mount Shasta to an elevation of uearly 10,000 feet. At the upper ends of the canyons their walls n^treat, and the valleys , become shallower, and spread out in fan shape, forming cirques against the mountain summit. The glaciers occupy cii-ques. Those of McCloud, Wintun, and Bulam glaciers are the best developed. The snow slides in from the sides and head of the cirque, and the corrasion is glacial. At lower levels the snow and ice melt, forming streams of water armed with glacial gravel and saud, with which to scour their beds and cut the canyons of the forest belt. The circjues are wholly abo\e the timber line, and are of glacial oiigin. The divides between them are usuall>- sharp, jagged ridges, whiles in the Canyon Zone they Jire bi'oad and even. lu this last ft^ature (the broad and even divides) is found evidence of the comparative youth of Mount Shasta, its slopes are suiooth; they have suffered^ but little from general degradation since the volcanic forces completed its construction. In this respect it is strongly contrasted with Mount Kainier, which has been deeply sculptured by ice and water; and yet Mount Rainier is less tlian halfway in the course of eiosion to- ward exposing its volcanic ueck, which occupies the vent thrt)Ugh which the lava came up to the surface, "^^^lile the early stage in the degradation of volcanoes does not differ nuitt^'ially from that of other conical mountains, the late stage in which the volcanic neck appears is peculiar and especially chai'acteristic. Thai iAlount Shasta has a great core of solid lava in its center, from which, wIk^u the coulees have been washed away, a cons])icuous volcanic neck may be develojied, there can be no doubt; but, if the process of degradation proceeds as now, without acceleration, it will be many centuries, even geologically considered, before the neck is fully brought to vieAv.

•JliS MOUNT SHASTA, A TYPICAL VOLCANO.

AuE. — The uphuildiu^ of Mount Shasta is but a matter of yesterday eouipaivd with tlie lapse of ages since the birth of some of its iieijjihliors. The (>oiiii)lex gi'oup of mouutains on tlie west, eml)raciug S<'Ott, Trinity, Sahnon, and tSiskiyon, all of which belong to the Klamath Mountains, are composed in large part of ancient crystalline i-ocks of both aijUeous and igii(>ous origin. Thi'ough tliese the Klamath and the Sacramento rivers have cut deep eauyous. The canyon of the Sacramento was cut ilown to Tiearly its present level, and the mouutains sculjjtured into existing forms, long before the eruption of Mount Shasta had ceased ; and a fieiy flood of lava, escaping from the southern slope of ]Mount Shasta, entered the Sacramento Canyon, and followed it for 50 nules.

Towering more than a mile above its neighbors, perhaps the youngest of the gi'oxip, Mount Shasta is the last of a long series of volcanoes in the Cascade Range, stretching northward to Mouut Rainier in ^Vashiugton. This range, composed chiefly of volcanic material, is cut across by the canyons of Coh;nd)ia and Klamath rivers. In the former, beneatli a thickness of 8,500 feet of lava, are found strata containing Tertiary fossils. At the southern base of Mount Shasta, in the canyon of McCloud River, similar beds of volcanic debris are found, but without fossils. It is evident that the main mass of the Cascade Range and its volcanoes originated in recent geologic times ; and from the fact that solfataras, fiimaroles, and hot springs are common on their slopes, they cannot be counted among wholly extinct volcanoes.

Active volcanoes occur in Alaska, but there is some doubt as to when and where the last volcanic eruption iu the United States south of Alaska may have oecixrred. The evidence seems con<'lusive that an eruption took place as late as 1843 from Monnt Baker, and also from Mount St. Helens in Washington.

Mount Shasta is a tyi)ical example of a large volcano. Its upbuilding resulted from long-continued series of intermittent eruptions. The attack of the weather increased with the height of the mountain, and reached its climax with the decadence of volcanic energy. During the brief period in which the weather has exercised stipreme control, the slopes of ]\Iount Shasta have been deei)ly cut with canyons, and circjues have been outlined about its lofty sumniit. In the course of geologic time it will be swept away, but for ages yet to come it will remain one of the grandest mountains on the face of the earth.

THE PHYSICAL GEOGRAPHY OF SOUTHERN NEW ENGLAND.

By Williaji Mokkis Davis.

Professor of Physical Geography, Harvard University.

Southern New England is for tlic most ijart a slanting up- land, reaching elevations of from fifteen hundred to two thou- sand feet in Vermont and westei-ii New Hampshire near the Massachusetts line, and descending gradually to the coast on the east and south. The upland is overlooked by occasional iuountains of moderate height, such as Monadnock: it is inter- sected l)y ninnerous valleys, deep and narrow like that of the Deerfield, or Iji-oad and ojien like that of the middlti Conneeti- cut. Its shore line is ragged, with I'centrant bays between pro- jecting headlands, and sounds behind outlj'ing i.slauds.

The heads of the larger buys wei'c early choscm as places of settlement, and there a number of thriving connnercial cities have now grown. The low coastal border of the upland near the cities is occupied by a comparatively dense suburban and rural population. The inner valleys serve as tlie paths of rail- roads leading to numerous manufacturing villages and cities. The higher parts of the ui)hiiid are spai'sely settled by a decreas- ing agricultural population, and the mountains above the upland are practically uninhabited.

THE UPLAND OF SOUTHEKN NEW ENGLAND.

General Features. — The gently slanting upland is the most important geographical feature of this region. Omitting from consideration for th<' jiresent the mountains that hero and there overlook it, and the numerous valleys that are woi-n beneath it, let us consider the form and origin of the upland itself. Ascend

(Copyriglit, 1895, by American Book Company.) 269

270

THK UPLAND OF SOUTHERN NEW ENGLAND. "JTl

a hill that i-cac-hes tlic general upland level, and noto how even the sky line is on all sides; how moderate the ine(iuality of the surface would be if it wei-c not for the few mountains that rise above it, and the many valleys that siidc below it. Looking aroTuid the horizon, the slightly rolling high-level surfaee of one hill after anothei- approaches the plane of the cireuiai- sky line. It re(iuires but little imagination to recognize in the successive hilltops the dissected remnants of a once even and continuous suVface, beneath wiiich the valleys of to-day have been eroded. The former continuity of the now separated hilltops is so mani- fest, when it is onee perceived, that it is well to desci-il)e tlie re- gion as an upland or as a dinsccted upland, thus emphasizing the original continuity of the now dissected upland areas, and at the sanu^ time comiteracting and corre<'ting the belief, jjiwaleut in the minds of those Avho dwell in our valleys, that southern New England is simply a i-eg^on of disord(U'ly hills.

Not less notable than the foi-mer continuity of the dissected upland is the want of sympathy between its suiface and the structure of the rock masses of which the ivgion is composed. The slopes and crests of the hills often expose their stru(ttural rock ribs in jn-ojecting ledges; the disoi-dered attitude of the rocks is plainly exhibited in stream banks, (piai'ries, and raili'oad cuts ; but, however they stand, they are evenly cut off when they reach the upland suiface, just as the fibers of a great tree ai"e cut across at the even surfai-e of its sawed stimip. This is an impor- tant matter, for upon it chiefly timis the correct interpretation of the oiigin of the upland.

The upland is most easilj^ recognized where it stands at a considerable elevation, for hero we find the strongest contrast between hilltop and valley floor. The broad, high-level areas between the DecM'tield and Westfield valleys, or the Westfield and Farmington valleys, in western Massaclnisetts, offer admira- ble illustrations of its character. The upland can thence be traced southward, ])ast many deep, ti'ench-likc^ vallej's, such as that of the Naugatuck above Watei'bury, Conn. It gi-adually descends to the sea level at the shore of Long Island Sound. The view westward from the summit of the Hanging Hills, near Meriden, Conn., sliows the upland beyond the Connecticut Valley lowland with a remarkal)ly even sky line. It truly resend)les a plateau thereabouts, and so it may be called. An excellent sight of the upland farthei- east may be obtained from Gj'eat Hill, a

it

1

'/

'5^

272

THE UPLAND OF SOl'THEKN NEW ENGLAND. 273

little novtli of Cobalt station, ou the Air Line Railroad, a few miles east of ^Middletown, Conn. Here attention is first attracted by the beantiful valley of the Connecticut River, ou its way to the Sound at Saybi-ook (of wliicli, more Ijclow); but, on turn- ing to examine the upland in which the valley is sunk, the even sky line is still ])erceived to be its most striking characteristic. Farther north, in Massachusetts again, the quiet hill town of SliutesT)ury, easily reached by stage or on foot from the Fitch- burg Railroad, near by in the valley of ]\Iill<M's River, commands a wide prospect over the even uphnid, and down into the valley by whicli the upland is there so deeply dissected. Near Gardner, ihi.) Fitchburg lini' passes over tlu.' divide between the basins of Nashua and Millers rivers, and traverses the upland for a short distance. Broad views then open out on either side, presenting the upland country in a very different aspect from that in which travelers by rail oi'dinarily see it; for most of our railroads fol- low valley floors. North of Boston, the hills back of Waltham, Arlington Heights, and the Middlesex Fells as seen from the hills of Somervillc, — or even from the State House dome, — exliibit a comparatively even sky line, gradually descending eastward to- ward Lynn. West of Narragansett Bay the ujilaiid has a well- defined, even-summit surface, gently descending southward, as in Connecticut ; and so on, at many other places. Thei'e is hardly a village in southern New England — except on the sandy low- land of the southeast — from which a willing observer cannot see a pai-t of the upland in an aftei'iioon's walk.

Okigin. — Still postponing the consideration of the sunnount- ing mountains and the intrenched valleys, let us inquire into the origin of the once even surface of the upland. At the time before the valleys wei-e worn in it, it was a broad, gently rolling plain of moderate^ relief, only here and there interrupted by the mountains that rose above it. It cannot have then been a young marine plain formed under the sea and revealed by uplift, like the coastal iilain which now borders our southern Atlantic and Gulf States ; or a young lacustrine plain, once the floor of a lake from which the water has been withdrawn, like the desert plains of Utah and Nevada : for plains of these classes consist of bedded and loose-textured sands and clays, whose nearly horizontal strata closely accoi-d with their almost level surface. The New England upland consists of rock masses of many different kinds, whose texture is for the most part thoroughly indurated, and whose at-

:.'74 PHYSICAL GEOGRAPHY OF SOUTHERN NEW ENGLAND.

titude is gi-eatly and irregularly inclined. Manifestly the ancient upland cannot be classed with either marine or laciistriue plains.

There are slanting or nearly level plains in certain parts of the world which have been formed by the weathering and wasting- away of a mass of overlying rock layers, thus exposing a horizon- tal or slightly inclined resistant stratum of indurated rock, on which further progress of weathering is long delayeil. Such, for example, is the upland plain in which the gorge of Niagara is cut ; but in these stripped plains, or structural phi'ois, as they may be called, there is necessarily a close sympathy between the shape of the surface and the attitude of the resistant stratum which determines it. Surely this is not the case in New England ; for here, although the rocks are indurated, they stand in all attitudes with respect to the upland surface, — here inclined to the east, there to the west ; here gently slanting, there steeply jilunging or even vertical. The generally even surface of the upland shows practically no sympathy with this diversity of structure, but passes indifferently across all the inclined rock masses. The New England upland cannot, therefore, have been a structural plain.

There is a kind of plain that results from the destructive ac- tion of weather and water, by which any laud area, whatever its original form, is worn down so smooth, and so close to sea level, that it cannot be worn any lower. Although thus easily and simply stated, the possiliility of producing plains in this manner is one from which an unaccustomed mind instinctively shrinks on account of the enormous time that it must recpiire. The small attention at present given to land sculjiture in the study of geography is here to blame. Early grammar-school teaching should present the general idea of weathering of rocky hillsides and the transportation of the rock waste down the slopes to the sea, thus preparing the way for understanding the great results of these simple processes when long continued ; yet nowadays even the teacher may hesitate to think that land erosion has anywhere in the world advanced so far as to consume high hills, and reduce them to lowland plains. This idea is not conunonly familiar, and it is generally given a cool reception when first met. Many text-ljooks now in use cite deep valleys as the best examples of long-continued erosion; but it is manifest that, whei'e the valley sides have wasted away so as to consume the interstream hills, a greatly increased period of erosion nmst have elapsed. Worn-down countries or plains of denudation, and not

THE UPLAND OF SOUTHERN NEW ENGLAND, 275

deep valleys, should therefore l)e iutroduced as examples of what erosion oau do if time enough is allowed ; and the earlier this im- portant generalization becomes familiar to young scholars, the more freqnentl}' and easily can they apply it afterwards.

Now we must inquii'e whether the ancient upland of New Eng- land, before the valleys were cut in its then even surface, was a plain of denudation ; and the methods of this or of any similar inquiry should be cai'efully and consciously perceived. We must, on the one hand, study the j^hysical features of the region under consideration until they can lu^ justly generalized ; we nuist, on the other hand, reason out wliat would be the essential pecul- iarities of a plain of completed denudation, guiding ourselves in this inquiry by accepted geologittal principles. We must then compare the results of these two lines of work; and if the ex- pectations of oui- reasoning match t he generalized facts of obser- vation, it may lie as a rule fairly maintained that the reasoning has led to a correct exphi nation of the facts, or at least that the explanation may lie adojtted provisionally while it undergoes further scrutiny. This method has already guided us in inquir- ing whether the New England upland was originally a marine coastal plain, a lacustrine plain, or a sti-ipped sti'uctural plain, the result being negative in each case.

The facts of form and structure of the New England uiilaiid have already been sufficiently stated in generalized form. They may be veritied l)y hundreds of observers in all jKirts of Massa- chusetts (except, as already stated, in the sandy southeastern lowland), Rhode Island, and Connecticut, as well as in southern Vermont and Now Hnnqishire. The theoretical expectations regarding a plain of denudation must now be reasoned out. Whatever the initial form and structure ' of the region, it- must be worn lower and low(n- as long as it stands still with resjiect to sea level, and suffei-s under the genei-al attack of weather and water. The valleys are deepened first, until the slope of their rivers is reduced to a gentle grade. ^Phe hills are much more slowly worn down; but as long as they have a slope to the streams, and as long as the streams descend to the sea, the wast- ing of the hills continues. The most resistant rocks are the last

1 It should hi' (ilistMvc.l thiit the tenu .•.Inwdirc is usimI throughout this moiio- Sraph to refer to the internal arranKoraent of roek masses, and not to the succession of superficial features, as it is sometimes employed in geogi-aphical descriptions. The latter use is objectionable.

271) PHYSICAL GEOGRAPHY OF SOUTHEKN NEW ENGLAND.

to be worn down, but all must go in time. When at last worn close to sea level, the surface must be practically indifferent to the attitude of the rock masses. There can be no essential sjtu- pathy between surface and structure, siich as has been stated to characterize young, unworn marine or lacustrine plains, or stripped plains. The almost sea-level surface to which a region may ultimately be reduced must pass indifferently across the structure of its rock masses.

The Upland is an Old Peneplain. — This peculiar feature — indifference of even surface form to disorderly internal struc- ture— now appears to be a common characteristic of the old upland of southern New England, and of a theoretical plain of denudation : hence the upland may be fairly enough provisionally regarded as an ancient plain of denudation. It should be noted, however, that, accortling to this exi)lanation, it is not necessary to suppose that the upland of New England or of any other similar region was worn down absolutely and completely to sea level, or haselcrcl, as it is generally called. The process of denudation may be interrupted in a penultimate stage, when the region had been rediiced to moderate i-elief, and before it had been worn down perfectly flat. It might then be called, not a plain, but a pexcplain, of denudation.

The discordance of the upland surface and the rock structure is so marked a characteristic of New England, and is so fuUy and reasonably explained bj' the theory of the penei^lain, that it would be fail" to conclude at once that the formerly even upland really was a peneplain, worn down under the long attack of the weather, if it were not for a possibility that smooth plains of denudation may be produced b}^ another process, namel_v, by the attack of the seashore waves. If a continental mass stand stiU for a long time with respect to sea level, while the sim continues to shine, the winds to blow, and the waves to roll, then the mar- gin of the continent will suffer from the beating of the surf : the sea will encroach on the land, eating it away, and reducing it to a comparatively smooth submarine platform at a moderate depth beneath the water surface. May not the New England upland have been formed in this way, and afterwards raised from be- neath the sea! The surface of the submarine iilatform would, like that of the subaerial peneplain, be indift'erent to the rock structures across which the shore waves had cut their way : hence the chief test on which we relied for detection of the peneplain

THE UPLAND OF SOUTHEKN NEW ENGLAND. 277

does not serve to distinguish it from the jilatfonn. What we now need is some further test by means of wliich these two kinds of plaius of denudation may be discriminated.

Tlie needed test is found in the ari-angeincnt of the rivers; but, while the argument thus far pursued is essentially simi>le, its fui'lher extension is unfortunately comijlicated, and partieularly so in its application to New England. It nuist suffice, therefore, to present it only in outline.

During the long-continued attack of the weather necessary for the pi-odi;ction of a subaerial peneplain, the little streams gnaw at their head waters, and search out the weaker rock masses on which to extend their valleys. As these growing valleys increase in length, they thus become well adjusted to the structure of the region that they drain. Penei»lains have, there- fore, not only a surface form that is indiifer(>ut to internal struc- ture : they have also a drainage system that is for the most part well adjusted to the weaker parts of the structure; and this adjustment is nuiintained or even furtlu>r improved if a new uplift of the region afterwards allows dee])er dissection.

During the long-continued attack of the shore waves necessary for the production of a l)road sul)marine platform, the valleys are extinguished as tlu^ land is cut away. When the platform is afterwards raised above sea level, and streams gather on it again, they assume such coursers as the slight inequalities of the njdifteil platform shall determine, and htmce have about as indefinite re- lation to structure as the surface has. Uplifted platfoi-ms have thei-efore, when they arise above the sea, and for some time thereafter, a drainage system that is essentially iiidiftVi-ent to the rock structure.

It would be easy to apply the test thus deduced if the geologi- cal structuiv of New England were as simple as that of middle Pennsylvania; but unfortunately such is not the case. The arrangement of the rock masses in the New England upland is excessively com})licat(Hl ; moreover, the glacial invasion (of which, more below) has been a disturbing agency by throwing many streams into new courses. It would be venturesome at jire'sent to make any gelieral statement regarding the adjustment or in- difference of our streams and structures, and the question would have to remain in doubt were it not for evidence tliat may be borrowed from New Jersey and Pennsylvania. The ujiland of New England is continuous with corresponding uplands in those

278 PHYSICAL GEOGRAPHY OF SOUTHERN NEW ENGLAND.

States,^ where the river test has been suoeessfiilly applied. The subaerial origin proved for the more southern peuepkiin may be fairly aeoei)ted for the more northern one as well.'-

KeFLECTIONS SUGGESTED BY THE OrIGIN OF THE UPLAND. —

^VTieu the belief clearly enters the mind that the upland of southern New England is really a peuej^lain of denudation, it arouses a munber of interrogative reflections. In the flrst place, inquiry springs up as to the amount of mateiial that has been worn away in the production oi' the ]>eneplain. Look once more at the character of the upland rocks : they are crystalline schists and gneisses for the most part, whose minerals are never formed at the surface of the land or on the floor of the sea, but only deep within the crust of the earth under great pressui'e and at com- paratively high temperatures. Besides these rocks, there are many intrasive gi-auites, felsites, diorites, and other igneous rocks; not loose-textured, slaggy, and ashy, like the eruptive rocks of volcanoes, Init compact and dense-textmvd, as if they had cooled under the heavy pressure of a gi'eat superincumbent load. It is only by long-<'ontinued and extensive denudation that the surface of the land can ai)j)roach rocks of deep-seated origin : hence it may be concluded that the initial siu'faee of the region stood high above the surface of the peneplain. Whenever the even sky line of the iipland is spread before the observer, it should be borne in mind that the i-ocks now exposed to the light of day were for long ages biuied in inner darkness.

Was the region, before the great denudation was accom- pUshed, a rocky, even-topped plateau, or a rugged uiouutain range! Look again at the attitude of New England rocks, re- membering that typical plateaus like those of Utah, New Jlexico, and Arizona, have horizontal structure, while tj-jncal mountain

• The Kittatinny ])i'iifi>laiu. See Tl>e Northern Appalachiaus, by Bailey Willis (National Geographie Monojcraphs, No. 6, p. 1S7).

- The full liiscnssion of this problem in its application to New England has not yet been undertaken. Along the southern border of the upland, a number of rivers that enter Long Island Sound seem to exhibit a rather marked indifference to struc- ture, from which the origin of the upland, or at least of that part of the upland, as a submarine platfomi, might be argued. But it may be answered that this indifference of streams to structure can be explained by superposition through the former in- land extension of the Cretaceous strata now seen in Long Island ; and that the Cre- taceous sea may have gained access to the region passively by the submergence of a previously denuded peneplain, as well as actively by cutting its way inland during the production of a platform. No certain settlement of this involved question can be given at present.

THE UPLAND OF SOUTHERN NEW ENGLAND. 279

liiiiges like the Alps and Himalayas are regions of deformed structure. Ancient New EngUmd certainly belonged to the hitter class. The disoi-derly and stc('])ly inclined rock masses may be seen at a hundred points on liiUlops and valley sides, in stieam Ijeds, railroad cuts, and quai-ries. The valleys of the Housatonic, Farmington, "Westfield, and Deerlield rivers all ex- pose deep sections in the Avestern upland. E.xtensive (piarries, such as those of Monson in the upland east of Si)ringfiel(l, are well worth visiting t'oi' the plain views that they afford of rock structure and attitude. The headlands of the coast frequently expose clean-swei)t ledges, where the deformed rocks can be ad- miraldy studied. They all teach the lesson of severe disturbance, as differeid as jtossilile from the jHacidity tluit jirevails among the .mcient sedimentary strata of the Ohio N'alley, where layer lies on layer in almost undisturbed horizontal position.

The NeAV England rocks are not only deformed in mass: they exhibit also at many i)laces the minute internal <leformities so characteristic of ivgions that have l)een crushed under a great overlying load, and so prevalent in regions that are mountainous to-day. On Hoosac Mountain t]ier(> is an old pudding stone or conglomerate whose once round pel)bles ;ne now di'awn out into strips, the rock assuming the charncter of a gneiss. Among tlie Berkshire^ Hills ancient slates are gnarled and crinkled into schists. At many points cleavage is more or less perfectly developed in the finer-grained rocks.

The crushing forces that caused the greater and smaller deformities cannot have been exerted after the peneplain was produced, for in that event they would have deformed the upland surface. The deformation of New England nnist have taken place liefore the great denudation. During the period of most energetic(leformation,Nc\vEngl;ind must li;ive had as tlioi'oughly a mountainous form as it still has a mountainous structure. In- deed, the most ])robable conclusion thatciui be reached regarding the anci<!nt topogi'aphy of the region raises its peaks to truly Alpine heights, clothes their upper slopes with snow fields, and fills their valleys with glaciers; and all these features should l)e restored in the pictures that tlu^ attentive observer menttdly sketches in his effort to represent the ancestry of the upland. Very slowly were the ancient mountains raised; much more slowly were they worn down, until now onlj' their base remain.s. New England is a worn-out niountnin range.

280 PHYSICAL, GEOGRAPHY OF SOUTHEKN NEW ENGL.VND.

The Peneplain in Geogkaphical Study. — It is worth while to stop our interrogative reflections here for a few moments to note the effect of this intorprotation of the New Eiighuid uphmd on the usual consideration of mountains in our geographical text- books. It is ciistomary to treat mountains empiricall}- as fixed geographical forms, permanently set upon the earth's surface. Such terms as nhl nioioitaiiis, or ironi-oi(t nioioitains, are seldom employed : the regions where these terms would be appropiiate are vaguely desci-ibed as hilly districts, with no sufficient indica- tion of their associated features. As a result, the scholar gathers no understanding of the nature of a region like Xew England ; for the characteristics by which its hills are distinguished from hills of other kinds, like those of the dissected portions of our South- ei'u coastal plain, are not clearly set before him. The empirical treatment of geography ordinarily adopted may be compared to an irrational system of botany that would place spi'outing acorns, full-grown oaks, and decayed oak stumps under different species. This is so manifestly alisurd that it seems to have no relation to the existing methods in geography, and yet it is a very fair illustration of them. The young ridges of southern Oregon, hardly altered by denudation from the constructional forms given Ijy ilislocatiou and upheaval ; the Aigorous Alps, long and severely deformed, and now deeply trenched by adolescent vallevs; the old mountains of Xew England, lomj and severelv deformed, and now broadly denuded till only their liases remain, — these three examples of mountain fonii may be fairly likened to the sprouting acorn, the mature oak, and the decayed oak stump ; and yet it is not the fashion to emphasize these rational relationships in the ordinary method of teaching geogi-aphy. Geography still retains too much of its old-fashioned, irrational methods : it has not kept pace witli the advance made by geology. In spite of what the geologist has learned abi)ut the evolution of geogra^ihical forms, the geographer still too generally treats them empirii-ally, and thus loses acquaintance with one of the most interesting i)hases of his su])ject.

The New England ujiland, recognized as a worn-down moun- tain region, — a peneplain, — soon comes to have value as a typi- cal example of this kind of geographical form ; and every such addition to the geograi)her's stock of t^'jies increases his appre- ciation of geography. In the beginning of elementary geography only a few simple t j^jes are described ; but, as the woi-k advances,

THE UPLAND OF SOUTHERN NEW ENGLAND. 281

more complicated types should be introduced, otherwise the sub- ject will always remain in a childish stage. Rivers are early taught by the desciiption of some average, mature example ; but in later years rivers of many kinds and in yiany stages of development should become familiar. ( 'oast hues are at first taught sinii)ly (IS the margin of tliclaud; Itnt afterwards tlicy may tie elaljorately suljdividcd and classiiiod according to their origin and evolution. 80 with mountains: a good vigorous mountain range, shown in pictui-es and desci-iljcd in nairative form rather than in terse definition, properly intro(hi<'es this lai-ge geograjilii- cal family to young scholars; but later on, many kinds of moun- tains must be recognized, young and old, as well as mature ; and of old moimtains no better example can be found tlian familiar New England. More will be said, later on, of this important matter of equipping the student of geography with a good assortment of type forms; but w(» must now return to matter more immediately in hand.

The Monadnocks. — In si)ite of all that has been written, it is still natural that the idea of wearing down a great Tuountain I'ange should Ije accepted ratliei' slowly. It is difiicidt to believe that all the hardest mountain nuclei can waste away. Some nn- consumed remnants of the ancient mountains of New England are naturally looked for, and they ai-e no sooner looked for tliau found. There is hardly any comprehensive view of the upland that does not reveal a few hills surmounting the sky line by some small measure of height ; and in certain i)laces the remnants still preserve a commanding elevation. One of the best points of view in New England for the exhibition of the even upland and the occasional remnant mountains tliat rise above it is Massamet, or Bald Mountain, near Shell)urne Falls, in northwestern Massachu- setts.' To the eastward, beyond the ('oniHu-ticut Valley, the sky line of the upland forms a lioi'izon almost as even as tliat of the ocean; Imt beyond in tlie hazy distance rises the blue dome of Wachuscitt, an isolated ennnence. Still more striking is the beautifid cone of Monadnock in the northeast, trnl>' of no great

, ' Tho [icoplo (if tliis inamifiicturiiif; town cm llip Deerfield River havp laiil nut an excellent jiHtli up the hillside, thi'ou>ch the woods, to a hij^h tower huiU on the sum- mit, from which a broad prospect, uninterrupted by trees, is opened on all sides. The round trip from the railroad station may be made on foot comfortably in four hours. — an hour and a half for ascent; the same time on the tower, ma]) in liand, stiidyiuf; the view; and an hour for descent. Much of the patliway is sliaded. The morning hours are best for the walk.

282 PHYSICAL GEOGKAPHY OF SOUTHERN NEW ENGLAND.

height among the mountains of the world, yet here imposing from the strength with which its solitajy pile emphasizes the evenness of the upland that it surmounts. It might well be mis- taken for a vokt^no, so symmetrioal are its slopes as seen from Massamet ; but, far from having been heaped up on a once level upland, ]\[onadn(K'k and its fellows are the last remaining hard- rock kernels of once much higher mountain masses, now nearly worn away.

There are not many Monadnocks in southern New England : the rolling upland is seldom dominated by any strong summits.

KiG. o. — Moiiailuock, from uiar Keiuu, X. H. (Photographed by J. A. French.)

The view from Great HiU, near Cobalt, Conn., already mentioned, discloses no remnant mountains distinctly interrupting the up- land sky line. Diufee Hill, in north-centr;\l Rhode Island, is the highest Monadnock of that State. The Ladd Observatoiy, on one of the hills of Providence, commands an excellent view of the up- land sky line beyond the Rhode Island boundary in southeastern Massachusetts. Only one little hiU in the distance distinctly sm-mounts the upland level, yet the sharp dej)arture of the hih from the ride of the A-iew attracts to it an amoi;nt of attention that is quite out of proportion to its small size. Blue Hill, a short distance south of Boston, is the most striking Monadnock east of "Worcester and south of the Xew Hampshire line, the upland in its neighborhood being well displayed in the hilltops above

THE VALLEYS m THE UPLAND. 2S3

Declhaiu. But on i)iissiug- northward into \'erniont, New Hanijp- sliire, and Maine, Monadnooks are eonnnon. The Wliite Moun- tains seem to be only a chister of uuconsumed remnauts; the scattered mountains of northern Elaine are pi-ohaMy of the same kind; tlie divi(h^ ])etween Connecticut and Cliaiiiplain (h-ainage in Vermont appears to lie ou the northern extension of the westei-u Uphmd of ^Massachusetts; and tlie peaks of tlie (xreeii Mountains are presumalily Monadnocks, hke (xreyh>ck and Mount P^verett farther south. But, hi spite of the nearness of these noi-thern States, they have not heen (>xplored with the upland peneplain and the Monadnocks in mind. No definite statement can at present be given as to the altitude of the ujjland in northern New England, or as to the degree of perfection that it attained. The region invites careful investigation.

The sunnuits of the Monadnocks ott'ei' extended views over the upland, and they should hv utilized as far as possible in teaching. An excursion to the top of Wachusett, for ('xami>le, is easily accomplished from a number of cities and towns in its neighborhood, and may be made extremely profitable to a class of young scholars. But just as we should, for the time being, assume the mental and moral attitude of a people if we would truly appreciate their history, so we shotild stand neai- the level of the upland, and not at that of a Monadnock above it or of a valley below it, if we woidd truly ai)preciate it as a pen<>])laiH. Mounds that rise but little over their sui-roundings, like Mas- samet near Shelburne Falls, or Great HUl near Cobalt, hardly deserving to be called Monadnocks, offtM- iho best opportunity for recognition of the real features of the upland.

THE V.U.LEYS IN THE UPLAND.

The Slanting Elevation of the Peneplain. — The most important I'eflection suggested by the view of the upland pene- plain of southern New England is yet to be stated, altliough it can hardly have escaped the attention of the reader. The pene- plain has been accounted for as a surface of denudation, worn down about as low as is possible by the processes of sul)ai''rial denudation ; reduced to a comparatively smooth lowland of faint relief, close to the level of the sea. Yet it is now a slanting up- land rising distinctly above sea level, and its surface is no longei- even and continuous, but is dissected by numerous valleys. Tn

2S4 PHYSICAL GEOtlKArHV t)F SOUTHEKN NEW ENdLAND.

the latest stage of the development of the peneplain, the rivers must liave Mowed on broad flood plains, adjoiiitnl by gently rolling low country on either side, liere and there surmounted by some surviving Mouadnoek. The very facts that the peneplain is now slanting upland, not a lowland, and that it is strt)ngly dis- sected by many valleys, at once suggest that it has been boilily elevated from its former to its present altitude so as to slant gently to the soutli and southeast; and that in consequence of this elevation tlie rivers that were powerless to cut tlieir channels any tlceper while the region was still a k)wland have been revived into a new cycle of activity now tliat tiie region has become an u]>l;nid. Only in this way can the dissection of the upland be accounted for. Uow the uplift was caused, or wlij- it came at one time rather than another, no one knows. Tliere is nothing to suggest that volcanic action liad anything whatever to do with it. There is nothing to suggest tliat it was violent or rapid, or attended by notable tremors or eartlupiakes. It can only be said, that, after a long time of comparative quiet, further smoothing of the peneplain was prevented by the occurrence of an ui)lift of unknown origin. The general date of the uplift can be given in geological chronology ; but it is siiflficient here, if any one asks when the uplift occurred, to say, " It must have been long enough ago for the valleys to have been worn out since." Tliat is a good geographical answer.

It is particularly important to recognize that the evidence leading to the belief in the uplift of the old peneplain is found entirely in the form of the region itself. It is not a conclusion based on the (>vidence of uplifted strata bearing marine fossils; for, while such fossiliferous strata occur both of ancient and modern dates, they do not bear on this part of our problem.' The uplift is known to liave occurred simply because the process

' For example, among the doformeil roeks of tlie ujiland tliere are ancient fossil- iferous strata at various points. Certainly tlieir fossils show that they liave been uplifted with respeet to the sea in which they were deposited ; V)ut, if it were not for the evidence found in the form of the dissected peneplain, it might be supposed that their present altitude above sea level had been given once for all, with the deforma- tion of the ancient mountains, and that these fossil-bearing rocks still stand above sea level only because they have not yet been ■(vorn down from the height originally given to them. Indeed, this opinion was very generally though rather vaguely held until fifteen or twenty years ago. The adojition of the oiiiuion now prevalent is entirely due to the recognition of the evidence based on the form of the peneplain. The first explicit application of this evidence to the case of New England was. I be- lieve, made by Professor B. K. Emerson, of Amherst College.

THE VALLEYS IN THE UPLAND. 285

of production of the peuepluiu demands that the region stood lower than now while the great denudation was in progress.

Those who have not studied geography outdoors may find some difficulty in accepting tliis argument. They are accustomed to saying, " Geologists tell us that so and so has happened ; " but it would be a sad mistake to treat this problem in so irresponsible a manner. When a teacher comes to the problem of the right- angled triangle, he does not say, " Geometers toll us that the sum of the squares is so and so : " he proceeds to explain the demon- stration. It is satisfactory to his own mind: he accepts it fully, and is willing to be held responsible for it. No teacher of geography should mention such a feature as an uplifted and dis- sected peneplain until she is fully convinced of its actual occur- rence, and of the reality and sufficiency of the processes by which it is explained. No teacher in southern New England should .say anything about' the home peneplain to her scholars until she can say, not, " Geologists tell us so and so," but, for example, " You can easily understand that the old peneplain has been up- lifted, for, if it had not been, no valleys could have been worn in

it. A good place to see this is ." While the teacher doubts,

the scholars find her explanations " too hard." When the teacher has an easy mind, the scholai-s will, I am convinced, find no diffi- culty in following the essence of all the explanations here ottered, provided thej' are presented very slowly, with plcMity of local illustrations in the field, and plenty of time for their digestion, part by part. The explanations and illustrations ultimately leading to such problems as are here treated, should be begun in the earliest nature study, and reviewed so frequently, and with such expansion of application, that the scholar makes his way to the understanding of the dissected peneplain step by step, as naturally and easily as he walks to school.

Only after this long introduction can the study of the valleys of New England be properly undertaken. They have been laid aside tVom consideration for a number of pages, but now they may be taken up with good appreciation of their origin and form.

Revival of the Old Rivers. — As soon as the elevation of the region began, the old rivers, .sleepily wandering over the peneplain, were awakened to the new task of cutting into the deep mass that had previously been safe below baselevel. Dur- ing the period of elevation, and ever since, they have been busy at this new task. Tli(> larger rivers have now cut their channels

286 PHYSICAL GEOGKAPHY OF SOUTHERN NEW ENGLAND.

dowu to a moderate grade, and the fiirther deepening of their valleys cannot be by a gi'eat amount as long as the land stands in its present attitude. The small branch streams still have steep courses : miich deepening remains to be done in their valleys. During the trenching of the valleys to their present depth, the side slopes have wasted and the valleys have widened, so that they are now nowhere precipitous. They are not vertical-sitled, like veiy young valleys, but have a more adolescent or mature expression. The peneplain is no longer a continuous upland siu"- face, but is thoroughly carved into a rugged lull country. The valleys are so numerous that it requires a distinct mental effort to recognize them as merely interruptions in the real geographical unit of the region.

Depth and Breadth of the Valleys. — The valleys of the chief streams differ among themselves in two particulars, — depth and breadth. They are shallow near the coast, where the up-

FlO. 4. — Decrlield Valley, above Shclburne Falls, Mass.

land is but little above sea level; they arc deep in the interior, where the upland may be a thousand or fifteen hundred feet or more above sea level. Close to the coast, our valleys are like those of Florida, where hardly any depth of cutting is allowed, because the whole State stands so near the level of the sea. In the interior the valleys are in nuitter of dejtth related to the

THE VALLEYS IN THE UPLAND.

•zsi

canyons that dissect the phiteaus of Arizona. In Itoth these cases the considerable elevation of the upland gives the streams permission to intrench tliera selves pi-ofonndly. Even the Grand Canyon of tlie (Jolorado is only about four times as deep as the Deerfield Valley in the view on the preceding |)age. The valley of the Naugatuck above Waterbury, shown in the iH>xt figure '

las

Fui. 0. — Naugatuck Valley, near Waterbury, Conn. {Photographed by L. G. Wcnttjate.)

a depth of about five hundred feet. It sliould Ix- noted that the second of these views, taken from the level of the upland, gives an excellent idea of the relation of tlu^ valley to the u])lifted peneplain in which it is incised, while the pictui-e of the Deertield Valley, taken from nearer the river level, gives only i]w impres- sion of being inclosed by rugged hills.

In respect to breadth, the most significant variation in the form of our valleys is controlknl by the resistance of tli(> rocks in which they arc^ worn. Where the rocks are of great resistance to weathering, or Jiinil, as we connnonly express it, the valleys are stiU rather luiri'ow and steep-sided ; and from tlus it nuist be concluded that thei-e lias not yet been time since the uplift of the peneplain for valleys to widen greatly in rocks of this character. But where the I'ocks weather rapidly, or are weak or ao/t, as we generally phrase it, the slopes to the streams have already wasted away so much that the vaUeys have become A\ide open.* The upper and lower parts of the Housatoni* "\''alley give excellent

*JH8 PHYSICAL GEOGRAPHY OF SOTTTHEKN NEW ENGLAND.

illustrations of the contrasted forms thus produced. The upper valley, generally called the Berkshire Valley, is broadly open along a belt of weak limestones, which have wasted away on either side to the hard rocks that inclose them on the east and west : the lower valley crosses the upland of western Connecticut, a region chiefly composed of resistant crystalline rocks, and here the side slopes are for the most part bold and steep. Indeed, here the rocks are so resistant that the river has not yet been able to cut down all of its channel to a smooth and gentle grade. In its course of HT miles from Falls Village, where it leaves the limestone belt, to Derby, where it meets tide water, this strong stream descends 560 feet. It is on account of so great a dis- tance over which the lower Housatouic has to cut its way across hard rocks, that its upper course, even on the weak rocks of the Berkshii-e Valley, is still held almost 1,000 feet above sea level.

Millers River offers another kind of illustration of the general principle by which the breadth of our valleys is governed. Its course leads westward near the northern boundary of Massachu- setts for about thirty miles to its mouth in the Connecticiit. On the way, the river crosses successive belts of hardei' and weaker crystalline rocks, trending about north and south. Where the rocks are weak, as between Athol and Oi'ange, the valley is wide- o])ened ; where the rocks are hard, as above Athol and below Orange, especially the latter, the valley is luueli narrower. Southward from Athol, towards Brookfield and Palmer, the penei)lain is much dissected by valleys that follow tln^ belts of weaker rocks; and, instead of resembling a continuous jilateau, the upland consists of a number of dissevered hills. One of the sharpest, most isolated of thes(^ hills is seen just north of Palmer, from the trains of the Boston and .Vlbany Railroad, foreshadow- ing what the rest of the ujiland nuiy l)e reduced to when the present cycle of denudation is further advanced.

East of "Woi'cestcM' ther(^ are so many belts of weak rocks that the upland is greatly interrupted ])ybi-oad valley lowlands; so much so, indeed, that the geogra]iher wlio is just beginning his outdoor studies may think that the eyes of faith are needed hereabouts to recognize the upland remmxnts. The lowland of the Boston basin is one of these broad interi*uiitions; Init along its northern bord(>r the upland may be seen with some distinct- ness. • The lowland around Narragansett Bay is another and even greater interruption, but the even sky line of the upland is

THE VAi,l.EVh IN THE UPLAND. 289

e;isily recognized on the east and west. The rocks of these low- lands are, indeed, so weak that they are already almost reduced to the present sea level, thus forming local peneplains of a second genei'ation. If one's studies were limited to these much-denuded districts, it would be very difficult to decipher their history ; but coming upon them fi'om farther west, where the upland pene- plain is much better preserved, and pi-ojecting its descending plane into the deiuided districts, their relation to the general upland is perceived without difficulty. No explanation of their evolution seems so fitting as the one here suggested.

The Connecticut Valley Lowland. — The finest of the low- lands by which th(> upland is liroken is that of the Connecticut Valley. Hei-e a belt of weak I'ed sandstones and shales, extend- ing from the northern border of Massachusetts southward to New Haven, has been for the most part worn down to a rolling lowland, five or ten miles wide near its extremities, and fifteen or eighteen miles wide alnrnt its middle. The uplifted peneplain, once evenly continuous across the sandstone Ix'lt, is now divided by the sandstone trough into eastern and western portions,which have nuicli tlie aspect of rugged plateaus when viewed from some of the occasional hills that surmount the vallt\v lowland. The lowland has the a)>pearance of a long, deep, l^i'oatl ti'ough when seen from the margin of the eastern or western upland.

Altliough called the Coiuiecticut Valley, this beautiful low- land riuilly consists of the wide-open confluent valleys of a num- ber of streams, of which the Connecticut is the master. The breadth of the lowland depends, not on the size of the Connecti- cut, but on the weakness of the rocks on which it is opened. This is particularly well shown l)y following the river thrcmgh the low- laud across Massachusetts and into tlie State of Connecticut. There the lowland continues southwai-d to the Sound; but tli(! liver turns eastward at jNIiddk'town, and enters a narrow valley in the eastern upland. Manifestly, then, it is the weakness of the sandstones and shales, and not the size of the Connecticut River, that has determined the lireadth of the lowland. There are few places when^ this important relation is better shown.

Of all the loc.il peneplains of the second generation in New England, tlie Connecticut Valley lowland is the best de- veh)ped. When viewed tVom the margin of tlie upland, east or west, the smaller inetiualities of its broad floor sink out of sight, and it seems to be ti-uly a jilain of completed denudation. At

29U I'llYSIC.VL UEOGKAPHY OF SOl'THEKX XEW ENGL.\ND.

the noi-tlieru border of Couuecticut, where the iiphiuds have a height of about eight huiub-ed feet, the lowbiiid liardly averages a hundred feet above the !<ea. Near the uortheru border of Massachusetts the uphuids rise to twelve or fom-teeu huudi-eil feet, but the lowlaud hardly reaches two hundred feet. One of the most important lessons to be learned from this is the remarkable contrast in the rate of weathering and wasting of the crystalline rocks that still retain the upland fonm, and of the red sandstones and shales which are already worn down to a lowland. Hand specimens of the two kinds of rook readily declare a difference in their hardness. The stonecutters who di-ess the blocks of Monson gneiss and Lougmeadow sandstone, so often used in architectural combination in recent years, will testify emphatically as to which rock is the more resistant ; yet it woidd hardly be expected, after the most careful artificial tests, that the long-continued natural test of weathering Avould have discovered so gi-eat a contrast in resistance as is indicated by the foi-m of the areas occupied by the two rocks. One stiU stands boldly up close to the height which both gained when the peneplain was uplifted, but from which the other has, as it were, melted away under the rays of the sun.

The same lesson is enforced when the observer stands on one of the upland hills near Middletown, and sees on the west the broad valley lowland, and on the southeast the steep-sided valley through which the lowland is drained. While the narrow outlet valley of the Connecticut has opened by wasting in the hard rock area only to its present restricted breadth, all the extensive valley lowland has been worn out. With the exception of the small pai't of the lowland that discharges to the Sound at New Haven, all the rock waste from the broad belt of sand- stones and shales has been carried down the narrow valley to the sea. This is the best example in New England of the general re- hition between open longitudinal and narrow transverse valleys. The uatiiral prepossession in such a case is that the broad valley lowland is older than the narrow outlet valley; and hence arise the mistaken explanations of tlie outlet as a "fracture due to some con^'ulsion of nature," or as the "channel carved by the overflow of a lake " that is conveniently assumed to have for a time filled the lowland. These eiToneous ideas have a wide acceptance among teacliers at present, although there is no shadow of e\'idence to support them in such an example as the

THE VALLEYS IN THE UPLAND. 291

one here under discussion. It is true that the bi'oad lowland is older than the narrow outlet valley iu topogi-aphic expression, but they are of the same absolute age, measured in centuries. The lowland was not made before the outlet, but only at equal jiace with it. Both are excavations in the uplifted peneplain. The excavation of both began at the tinu^ of the uplift. The deepening of the downstream outlet controlled tlie deepening of the upstream lowland; for tliis relation always obtains between the downstream and the upstream portions of a river. It is in breadth, not in age or dejyth, tliat the valley lowland and the outlet valley are unlike, and it is plain that the matter of breadth is entirely controlled by the nature of the rocks in which the valleys are excavated. "With so excellent an illustration of this principle as the Connecticut affords, it is to be hoped that its true explanation may soon be introduced iu our elementary teaching.

The relation of the longitudinal and transverse valleys is shown again in the long Berkshire limestone valley and its trans- verse outlet by the lower Housatouic, as already mentioned; but this is less conspicuous than the case of the Connecticut. The latter is, howevei', overshadowed Ijy the Hudson, which drains a part of the great Aitpalachian Valley through the deep gorge in the Highlands. The same relation is exhibited by the Delaware, the Susquehanna, the Potomac, and tlie James, as well as by innumerable smaller Appalachian streams, that drain open inner longitudinal vaUeys through narrow transverse gorgt^s oi- iratcr (/(tps. All the rock waste of the open inner valleys has been carried out through the narrow gorg(»s. Nothing less than the sight of one of these examples will do justice to the impoi'- tant lesson that they teach.

The Lava Ridges of the Connecticut Valley Lowland. — Recall for a moment the Monaduocks that stand over the uplands like monuments of dej^ai'ted mountains. Their occurrence should lead us to expect that residual eminences might occur on the local peneplains of the second generation. Such younger Monaduocks are, in fact, a])undant. The Boston basin counts them by the score, especially in the area of the Roxbury pudding stone ; but the best examples of these residuals occur within the Connecti- cut Valley lowland, aud some of these are of particular interest from their relation to the ancient volcanic history of the region.

Long ago — long before the peneplain of to-day was made, uplifted, and dissected — the red sandstones and shales were ac-

292 PHYSICAL. GEOGKAPHY OF SOUTHERN NEW ENGLAND.

cumulated in a trough or estuary between eastern and western highlands. It was during the deposition of these strata that the famous " bird tracks " — really rei)tilian tracks — were made upon successive layers of mudtly sand. The museum of Amherst College contains an extraordinary collection of them. For the geographer, the floods of lava or trap that were at several times poui-ed out over the sandstone strata, and afterwards buried by later deposits, are more important. The molten lava spread over the even floor of th(^ muddy estuary in broad sheets, many miles in length and breadth, and from one to four hundred feet in thickness. Some dikes and sheets of lava were diiven in among the sandstone beneath the surface. At last the further accumu- lation of deposits in the estuary was stopped by the distiirbance that gave the peculiai' tilted and broken structure to the belt of red sandstones ; and then it was that long-continued denudation produced the penei)lain that has been our chief theme, leveling otE the crystalliue highlands east and west, as well as the up- turned and dislocated blocks of sandstones, .shales, and lavas. It would requii-e a special monograph to do justice to the particular structures of this interesting region. Let it now suffice to restore the picture of the evenly denuded surface of the sandstone belt as a part of the old peneplain between the less smoothly denuded areas of crystalline rocks on the east and west. The sandstone beds generally dip underground eastward, and among them are the various sheets of lava, much dislocated. Now, when the fur- ther smoothing of the peneplain was stopped by the slanting up- lift of the region,the sandstones and shales wasted away with com- parative rapidity ; but the trap sheets and dikes resisted erosion strongly, and soon came to have a distinct relief above the wast- ing sedimentarj- beds. Even when the latter are reduced to the open lowland form that they have to-day, the hea^-ier sheets and thicker dikes of trap retain a great part of the height to which they wei'e uplifted, thus simulating the behavior of the hard gneisses and schists of the upland.

As the lava sheets dip eastward with the sandstones, the western face of the ridges exposes bold outcropping ledges, de- scending precipitously to long talus slopes of loose rocky waste, which covers the underlying sandstone beds ; while the eastern or back slope of the ridges descends more gradually with the slant of the lava sheets, and the next overlying sandstone beds are found only near the foot of the slope. Mount Tom, near

0

THE VALLEYS IN THE UPLAND.

293

Nortliaiupton, Mass., and the Hanging Hills, noai- Meriden, Conn., are among the finest examples of these trap ridges. From their summits one may look evenly aei-oss to the njilands on th(^ east and west, appreciating the plateau-likci sniootliiicss of their hill- tops; one may survey the broad valley lowland beneath, with its patchwork of field and woodland, and its mnny villages. Various

KiG. G.

-South M()Uiit:iiii, Ilaiii^iiiK Jlills. MciicU'ii, ('(inn. {Photographed by W.H. C. Pyiichon.)

other ridges belong to the same range, and ai*e, indeed, the out- cropping edges of tiie same lava sheet; the various notches oi- gaps by whi(!h the individual mountains are separated being due to dislocations of the sheet made at the time when the sandstones and the included lava beils were tilted. Mount Holyoko and Mount Tom, on th(^ north; Talcott Mountiiin, west of llar1foi-d; the Hanging Hills, Lamentation and Higby mountains, near ^leri- den; and Totokct nnd P(Uid (Saltonstall) mountains, east of New Haven, — are conspicuous meiidx'rs of tlie scries, and are all parts of a singlt^ lava bed.

East and West rocks, near New Haven, and the lon.<r north- ern continuation of the latter to (lavloi-d Mountain, are tlie chief

294 PHYSICAL GEOGRAPHY OF SOUTHERN NEW ENGLAND.

examples of ridges formed on intrusive lava sheets ; these ha\dng been driven in between the sandstone beds, instead of being poiu-ed out over their snrface. Monnt C'ai'mel and the Blue Hills, soutliwest of Wallingford, have a peculiar interest from marking the site of great dikes or iiccl's of lava. In all probaViility they are the roots of the volcano or volcanoes from whicli the lava sheets of the Meriden district were erupted. Similar but smaller necks have been found on the southern side of Mount Holyoke range in Massachusetts. Occasionally the lowland is surmounted by ridges of resistant sandstone (as Deerfield Mountain and the Sugar Loaves, above Northampton) or of conglomerate (as Mount Tob}% north of Amherst), but these are seldom conspicuous.

The Berkshire VaUey is also varied bj^ a number of isolated hills or mountains. Here they consist of resistant schists that stand above the limestone floor. Greylock is the chief of these ; for its summit not only lises above the Berkshire VaUey, but dominates the upland levels on the east and west as well, reach- ing the greatest altitude of any mountain in Massachusetts. Smaller and lower residuals are seen soutli of Pittsfield, where they contriljiite largely to the attraction of the picturesque dis- trict about Stockbridge and Great Barrington. Bear Mountain, in the.extreme northwestern part of Connecticut, the highest sum- mit in the State, may be, for oiu- purposes, hkened to Greylock.

On any of the higher trap ridges in the Connecticut Valley, the lesson of rapid and slow wasting of weak and hard rocks may be reviewed to advantage. The meaning of the geogi-aphical forms there tlisplayed gradually becomes so distinct that we need not say, " The lava sheets are harder than the sandstones, and hence the lava stands up in ridges, while the sandstones have been worn down to a lowland," but, " The lava sheets stand up in ridges, while the sandstones occupy the lowland : hence the lava must be much harder than the sandstones." The ridges do not owe their height alcove the lowland to any local uplift, but simply to retaining, in virtue of their hardness, much of the li eight which the weaker sandstones have lost. ^Vhere relations of this sort are clearly ajijireciated by geographers, it will require no argument to i)ersuadc them that the processes and results of land sculpture should form an essential part of geographical training.

Distribution of Population. — It has already been stated that the valleys and lowlands are the seats of the greatest part

THE VALLEYS IN THE UPLAND. 295

of our population, while the uplands are sparsely occupied. The full reason for this wiU not be perceived until the relation of

valleys to bays and harbors, and the origin of the watcn- i)owers of the valley streams, are explained; but the broad fact is easily appreciated. Look, for example, at the western upland in con- trast with tlic Berkshire and the Connecticut valleys west and east of it. On the upland itself there are quiet, out-of-the-way hUl towns, like Savoy, Florida, Peru, Monterey. It is through these hill towns that the pedestrian should plan his excursion, if he would escai)e from the ))ustle of the world heueatli, and find still preserved the quiet old New England ways. It is a district of smaU-field farming, too rugged for general cultivation. The patches of timber land sup])ly wood for small local industries in the villages, and i>ulp for jiaper mills in the valleys; ])ut to gain a living there is harder work than New Englanders even have cared to face, and they have either descended to the gi'owing manufacturing towns at lower levels, or they have moved out West to prairies and plains. Abandoned fannhouses on the side roads tell the story with sometliing of a dreary intonation, — the garden patches lost in wee<ls, the apple orchards gone to waste, the pasture lots overgrown with bushes and briers.

The narrow valleys within the upland have thriving vUlages, connected with the rest of the world by railroad lines. Here the farmers from the upland come down to trade ; here manufactur- ing industiies are established in great varietj% — cutlery works and shoe-peg shojis at Shellnirne Falls in the Deerfield Valley, emery works at Chester in the Westfield Valley; while nearer the great market of New York City, along the Farmington and Naugatuck valleys in the western upland of Connecticut, hard- ware, tools, clocks and watches, and lirass goods of every de- scription, are produced. It would lead into the d(>batable ground between geography and history to recount the causes that have de- termined the growth of these manifold industri(>s. Suffice it for the present to note that they arc strictly limited to the valleys.

Emerging from the nai-row valleys to the more open valleys, we find, on the west. North Adams, with cotton and woolen mills, and boot and shoe shops; Williamstown, with its college; Pittsfield, with varied manufactures and an active trade with the surrounding agricultural region ; Dalton and Hinsdale, witli great paper mills, in a side valley descending from the liills on the east side of the limestone belt. On the eastern side of the Berkshire

29G PHYSICAL GEOGRAPHY OF SOUTHERN NEW ENGLAND:

phitenu the contrast is much strouger between the rugged uphmd and oi)eu lowland ; for the Connecticut Valley lowland is longer, broader, and lower than the Berkshire \'alley. Its smooth fields tempted early settlement from the Colony of Massachusetts Bay. Many populous cities and towns are built upon it; railroads traverse it lengthwise and crosswise; manufactures tlirive; schools and colleges not only educate the youth of the valley, but attract boys ;iud girls from the upland, and young men and young women from all over the country; products suggestive of a mild climate, such as tobacco and jteaches, come from the valley farms ; garden seeds are raised as an important article of trade. And nil tlie uulikeness of the lowhmd to the uphmd is because the rocks of the one have wasted away, while those of the other have, comparatively speaking, lield fast. This is the imin-essive lesson of the dependence of the manner of life on the sculpture of the land, that our geographies should teach.

Near the coast, where the contrast between uj>land and low- laud is less market! than in the interior, the control exercised by the form of the land on the distriVmtion of pojmlation and in- dustries is not so striking as farther inland, but it may genendly be perceived in a gi'eater or less degree. Nearly all the suburban (.'ities and towns around Boston are on the floor of the basin. Tlie upland of the Middlesex Fells and the Monadnock-like Blue Hills are reserved as Avooded public parks. The numerous mauiifacturing A-illages of eastern Massacliusetts and of Khode Island are on comparatively low ground; Marlboro and Spencer (shoe towns), and (birdner and Templeton (cluur towns), being almost the only exceptions to tliis prevailing rule.

REVIEW.

A paragrajih may be given to reviewing what has been thus far exi>laine(l. The upland of soutliern New England serves us as the type of a peneplain, now ui>lifted and well advanced in n second cycle of denudation. Monadnock is a standard example of a residual mountain that rose aliove the peneplain when it was still a lowland, and tliat continues to dominate the i)enei>lain now that it has become an upland. The Deerfield Valley exiiil>i1s a moderate advance of the processes of dissection that will in time reduce even the hard-rock u])land to a lowland. The Con- necticut Valley lowland is a typical example of a local peneiilain

itEViEW. 297

of the secoiul generatiou, already developed on a belt of weak rocks, and inclosed by the adjoining hard-rock upland. Mount Tom is an admirable illustration of a residual mountain of the second generation, bearing the sanie relation to tlie valley lowland as that which Mouadnoek bears to the general upland. In Vir- ginia, residual nioiintains of this later generation liave been called ( '<if(>cti)/.s, taking the name of one of them to rejn-esent the class ; and when our isolated hills come to be recognized as remnants surmounting the earlier or the later peneplain, the two terras Moiiadiiocl-s and Catocfii/s may be eni]>loyed to designate tlie members of the older and younger families.

Another ])aragraph may be allowed to cautioning the reader against forming too i-igid and artifrcial conceptions of the natural processes liere referred to. It must not ])e thought that tiie land stood absolutelj' still during all the long period of ei'osion by which the peneplain of the uplands was produced. Many oscillations of level probably took ])lace, during which erosion was hastened or retarded. All tliat the occurrence of the pene- plain demands is, that the oscillations of level were not of great measure, and tliat the average stand of the land remained close to the level of tlie i)eneplain for a long time. Again, it nnist not be tliought that the erosion, by which the very ancient iriountains were laid low and tlie peneplain of the upland was produced, was all accoini)lishe<l dining one uninterrupted <'ycle of destructive work. Diu-ing the wasting of the ancient moun- tains, the land may have had several successive cycles of erosion, sepai'ated by tiplifts and deformations of greater or less value. In each of these cycles the surface of tlie land Iiiay liave l)een worn down more or less completely to the appropriate baselevel. Hence we are probably in error when speaking of the local ]»ene- plains of the vaUey lowlands as belonging to a srcoinl genei'ation, and tlms inii)lying that the peneplain of the upland was of the first generation. The upland i)eneplain is truly the oldest tliat has j'et been clearly recognized ; but perhaps, when the sctdpture of tlie Wliite ^Mountains and of the Adirondacks is carefully studied, still older iiiid higher peneplains may be discovered, as the.v have already lu'cn in the highlands of Nortli Carolina. Caution would therefore suggest tiiat tlie peneplain of our ujiland be referred to, in algebraic tertns, as of the vi\\ generation : \\w local peneplain of the lowlands would then l)e of tlie {n H- l)th generation. Still further, it nnist not be imagintul that the

298 PHYSICAL GEOGllAPHY OF SOUTH EUN NEW ENGLAND.

gi-eater deformation liy which the aiicieut mouutairis were pro- duced was the result of a single period of disturhance: various successive eiforts of crushing and hreaking tlie ci'ust of the earth jirobably occurred, and at some iiiulctiiicd time between the first crushing and final weanng down to the i)eueplain level the ancient mountains gained tlieir greatest height. It may be noted, however, that the latest serious deformation of the New England region was the one by which the sandstones and lava sheets of tlic Connecticut Valley belt were tilted and broken. The slanting uplift of the peneplain to the upland altitude seems to have been accomi)lished without pei'ceptible breaking, and with only a slight warping.

THE GLACIAL INVASION.

The liujits of this monograpli prevent more than a brief con- .sideration of two remaining subjects, — the glacial invasion, by means of which many characteristic geographical details were de- termined; and the associated depression of the land, as a result of which the lower parts of many valleys were changed into bays. Hence we nuist proceed more rapidly to direct assertion.

Vakious Forms assumed by Glacial Drift. — Just as Green- land is now ice-covered, so was New England once ice-covered after the general features of upland and valley liad been de- veloped. The ice sheet was thick enough to bury our Monad- nocks. It crept slowly down the general sloj)e of the upland to the south and southeast; it scraped along all tlie loose soil that it found ready made, it plucked many a bowdder from projecting ledges, and it wore down the rock surface somewhat lower than it had been; it was jn'csumably more active in deepening the soft-rock valleys than in rubl)ing down the hai'd-i-ock hills. If the ice sheet had lasted a very long time, or acted with very gi-eat energy, it might have left the rocky floor of New England clean-swept and bare ; but as a fact the greater ])art of the plunder that it had gathered was dragged along for only a moderate distance, and now lies spread irregularly over our province as a sheet of drift. The lowest mendjer of the drift, lying directly on the scored rock surface, is an unstratified, com- pact mixture of all manner of materials, coarse and fine ; this is called hon-hJpr clai/ or till. Its surface is generally smoothly roll- ing. Here bare ledges i)rotrude thiough it; there its thickness

THE GLACIAL INVASION.

2!»!»

locally increases, so that it assumes the form of rouuded hills, called drumlins, averaging half a mile in length and toward two hundred feet in height. Many of these may bo seen on the up- land between Speucer, Mass., and Pomfret, Conn. They occur in lowlands also, as on the floor of Boston basin and on the Con- necticut Valley lowland about Dui'ham. So inuch of the drift as was dragged, carried, or washed along to the fartliest margin of the ico sheet formed there a aeries of uneven liills inclosing manv

Fig. 7. — l)i'umliii, Grotuu, Muss. (Photoijraphcd by G. £f. Barton.)

an undrained hollow among them, and fronted by a plain of washed sand and gravel spread forward by the escai)ing ice water. Ilill i-aiiges of this kind are called fcrwiiial moraines. lihode Island ^jossesses an excellent exanii)lc near its southern coast, west of Point Judith. Southward from Plymouth, Mass., morainic hills may be traced far around the cui've of Cape Cod. As the ice sheet was hually melting away, much gravel, sand, and clay were washed forward from its irregularly r(>treating edge, and lodged in valleys and lowlands, sometimes taking the shape of gravel ridges, formed in tunnels under tiie ict^ near its margin, and then named cskcrs, like the so-called" Indian Ridges" at Andover, Mass. ; sometimes accumulating in sand and gravel mounds, formed in cavities close to the ice edge, and then called

300 PHYSICAL GEOGIUPHY OF SOUTHEUN NEW ENGLAND.

kames ; sometimes spread out in smooth flood plains, especially along the lai-gev stream courses, but now partly washed away, and thus forming our well-known r'tvei- terraces. The irregular distribution of tlie drift has obstructed mauy valleys, and thus formed our numerous lakes and ponds. The streams, more or less displaced from tlicir well-graded channels of i»reglacial time, have here and there cut down through the drift upon buried rock ledges ; and thus our rapids and fallfe have been produced.

GrEOGEAPHICAL CONSEQUENCES OF GlACL\E AcTION. — Although

strictly su])ordinate to the stronger features of uplands, valleys, and lowlands, it is manifest that all these minor drift forms are important as geogi'aphical details, and as such they should have due consideration in our home teacliing. Glacial action had no share in the evolution of Florida and Texas, and it would there- fore^ be a comparatively irrelevant subject in Southei'n schools ; but in New England, glacial action has been a more important factor in our geographical development than the Indians ever were in our historical development. The glacial elements in our geography have distinctly affe(?ted the course of our history from beginning to end, while the Indians were after a time pushed aside. The hills that guided the Pilgrims fi-om Proviucetown across Cape Cod Bay to Plymouth were the moraines of Manomet. The broad drift plains of the Connecticut were early sought out as places for settlement when the rugged uplands that sepa- rated them from the colonies of the eastern coast remained a wilderness; tlie many "fields" — Springfield, Northfield, West- li(4d, Greenfield, Decrfield, and tlie rest — all owe their surnames to the smooth drift floor of the vaUey lowland. Tlie last battle of King Philip's war was fought in the mai'shy district to which the Indians had retreated behind the terminal moraine of south- ern Rhode Island. Tlie small smelting furnaces in wliicli iron was made in New England 1)efore the daj's of railroads, were supplied with bog ore that was taken from shallow glacial ponds or marshes. The lakes that often serve as reservoirs — to flood streams and wash logs down to the mills, to store water for fac- tories, and to supply water to cities and towns — are all of glacial origin. Beacon Hill, Bunker Hill, and the hiUs of Somerville, on which earthworks were thrown up during the Revolutionary sti-uggle about Boston, are all drumlins. The plentiful supply of sand and gravel that has made the filling of Boston Back Bay comparatively inexpensive has all come from kames and sand

THE COAST LINE. 301

I)lains a few miles up the valley of the Charles River. The water power around which so uiueh New England capital has been invested, and about which so large a share of New England population is gathering, is all a consequence of the glacial inva- sion ; and, although steam has in recent years been largely added to water power, it remains true that the beginning of the gi'eat industries of Fall River, Lowell, Manchester, Lewiston, Paw- tucket, Waterbury, and many other places, depended strictly on the falls ill the streams on which these striving cities were Ijuilt. The occurrence of waterfalls not only in the small head-water streams, but also on the lower courses of the larger rivers, is peculiarly characteristic of their origin, and peculiai-ly important in their economic relations; for thereby the factory towns and cities often gain lai'ge volumes of water in the fall, combined with situation not far inland.

THE COAST LINE.

The Uepkession of the Land. — When our valleys are fol- lowed down to the sea, we find no deltas built forward by the streams, in spite of the large amount of rock waste that has been washed out from the upland during its dissection. On the contrary, before the general shore line is reached, the broadening floor of the valley is flooded with tide water, and the running river is transformed into an estvuiry or a bay. The simplest explanation of all this is, that, since the valleys were excavated, the region has svift'ered a moderate depression, whereby the up- land margin is sunk below sea level, its outer hills standing up "half-seas over" as islands, while the lower ends of its valleys are drowtied. The estuary of the Thames below Norwich, Conn., is as beautiful an exainple of a drowned valley as can be found anywhere; it shovfld serve; New Englanders for a type of the many other examples of the kind elsewhere in the world. Narragansett Bay is but the submerged i)art of a lowland that is otlun'wise in many ways comparable to the Connecticut Valley lowland. The tliree rivers, Pawtux(>t, Blackstone, and Taunton, that once were only branches of what may be called " Narragan- sett River," are now converted into inch^pendent river systems by the drowning of their truidv; and here again we have a type example, in terms of which many cases in foreign lands may be easdy described. The fringing islands along the coast of Maine

30*J I'HYSICAL GEOaRATHY OF SOLTHEKX NKW EN(iLAXl).

are the half-dvowiied hills that once surmounted tlie intervening valley flooi-s, the latter being now submerged by long arms of tilt' sea. Norway and Patagonia are best tauglit after these home illustrations are appreciat^'d.

Modification by 'WA^T.s and Curuexts. — Since the land and sea assumed their present relative position, the waves and the tides have effected certain signiticant changes in the form of the coast ; and here we enter upon a subject that deserves as delib- erate a treatment as has been given to our dissected peneplain. In a general way the changes along the sliore tend to promote simplicity of outline : the islands are in time cut away ; the head- lands are cut back ; and the bays are l)ridged across with bars, and filled with deltas and tidal marshes. Given time enough, and the irregular margin of New England woidd be cut back into long, smooth curves, like those of northwestern France, where the sea has made great inroads on the land; but time enough has not yet been allowed. ^Tiere oiir coast is rocky, it has not as yet suffered much change : the resistant headlands are not yet cut back into cliffs of notable height, and the bays are as a iiile too deep yet to have been filled by deltas or inclosed by bars. But whei-o the coast consists of ghicial drift, it lias already, in the present cycle of shore action, been nni<-h altered, the amount of modification depending chiefly on the openness of exposure to the strong waves of the ocean. Tiie shore along the northern side of Buzzard's Bay is still extremely irregular, its headlands and bays hardly being changed from the outline they had when the sea first lay at its present level. Tlie southern side of Cape Cod, somewhat protected by the outlying islands, still retains something of its original irregular outline, although its headlands are partly cut back, and its liays are bridged across, all uniting in swinging curves of greater or less radius. The southern side of Martha's Vineyard is much simpler, for here stronger waves roll along the shore, and the coast is reduced almost to a straight line ; half the headlands being already con- sumed, and only half the liays rtMiiaining. The outer side of Nantucket seems to have suffered a still gi-eater loss, for the headlands that once separated the little bays of its coast are now cut back so far that only the smallest remnant of the bay heads can be detected. The eastern side of Cape Cod is for the greater part a long straight cliff of clay and sand, surmounting one of the finest beaches in the world. Here no trace of the original

I'HE COAST LINE. 303

iiTt'guliir shore line remains. When the coast line is .studied carefully on the plan thus suggested, — first considering the manner in which the original coast line was determined, when the land and sea took their present relative position ; then con- .sidering theclianges thus t'ai' 2)rodu('ed in the original coa.st line V)y wave and cin'rcnt action, — it acquires the same quality of en- livened interest that is attached to the study of the development of laud forms : it becomes a subject worthy of special treatment. Geographical Consequences of Coastal Foum. — Some of our coasts are almost uninhaltited, becau.se they have no har- borage ; for example, the matured cliff coast on the " l)a(;k" or east side of Cape Cod, the adolescent .southern coasts of Nantucket and Martha's Vineyard, and the coast of Rhode Island west of Point Judith. The harbors among the many outer islands of the half-drowned coast of Mainc^ ha\e developed no large cities, Ijecause the islands are too small and too disconnected to favor the concentration of population. New Ham]ishire, ha\dng tlie smallest water boundary of any New Englaiul State, is the only exception to the rule that each State has its lai'gest city on a harbor, — Portland, Boston, Providence, New Haven, and Bur- lington, all attest the rule, — and l)efore inland manufactures were developed New Hampshire itself made no exception. All these harbor cities except Bui-lington have grown from early colonial settlements, in which good harborage was the chief ele- ment in determining location ; but the causes which have led to the greater gi-owth of certain harbor settlements than of others are generally to be found in some complicated relation between coast and interior; partly also in political influences, such as ac- company the location of a State cajjital ; and partly in seniority of settlement. Some cities on drowned rivers have the advan- tage of tide water a number of miles inland from the general coast line. Bangor, Augusta, Norwich, illustrate this relation.

conclusion.

It is only after a clear perception of the forms of the land is gained by tracing out their development that the careful teacher or the serious student is prepared to undertake the discussion of the relation of geography to history. In no way so well as by modern physiographic methods are the facts of land form bi'ought clearly before the mind. Throughout this monograph a knowledge of the development of land forms is not urged upon

304 PHYSICAL GEOGRAPHY OF SOl'THERX NEW ENGLAND.

the geographer as an end in itself, — although it may truly be re- garded as a worthy end of s^tudy by those who wish to devote their whole time to it, — biit as the best means to another end; namely, the ai)[)re('iation of the facts of land form which consti- tute the foundation of all thorough geographical study. It is often maintained that a devoted study of the facts themselves, without regard to their moaning or development, will suffice to place them clearly enough before the mind; but this vieAv is contradicted both by general experience in inaiiy subjects where rational exiilaiiation has replaced ein]iii-i('al generalization, and by the special experience of geography as well. Left to itself as an empirical study, in which the development of land foims was hardly allowed to enter, it has languished for many years, until it became a subject for continual comi)laint. Gradually be- ginning with easy examples like sand diuies and volcanoes and deltas, simple explanations of form as a result of process were admitted. To-day it is only by those who fail to see the direc- tion of geographical progres.s, and who are ignorant of the prog- ress already gained, that objection is made against the effort to bring every gecigraphical fact under the explanatioii of natural processes. No one of active mind can look across our upland and fail to gather increased pleasure and profit from understand- ing its history. No one who looks i;pon geography as the study of the earth in relation to man can contemplate the contrast be- tween glaciated New England and non-glaciated Carolina with- out inqrdring into the meaning of the contrast : he might as well study the Sahara and tlie Sudan withoiit asking the i-eason for the dryness of the one and the moisture of the other. It is a mistake in this day to speak of the many islands along the coast of iMaine, and not bear in mind that they result essentially from the lialf-drowning of the margin of the dissected upland; or to mention Narragausett Bay and the estuary of the Tliames with- out remembering that they are only drowned valleys, one wide, the other narrow; or to contrast the rugged coast of Buzzard's Bay with the smooth outer side of Cape Cod, and fail to see that one is still young while the other is already mature. It is as much in the spirit of jirotest against the omission of pliysio- grapliic explanations in the common-school teaching of our home geography, as in the desire to bring forward the salient physio- graphic features of southern New England, that this monogi'aph has been \vi'itten.

THE SOUTHERN APPALACHIANS.

By C. Willard Hayes.

THE PKOVINCE DEFINED.

Draw a line from the most easterly point of Kentuckj-, south- eastward across Virginia and North (Jarolina, to Cape Fear on the Atlantic. This will form the bouudaiy between tlie Northern and Southern Appalachians. In the northern division, described by Mr. Willis in Monogi-aph No. 6, the most striking character- istic is the large number of parallel linear ridges occiipying the central zone between the Blue Kidge and the Alleghany Front. Southward from the line above indicated the linear ridges de- crease in nuiuber and importance; the central zone becomes a true valley, bounded on the east by a broad complex mountain belt instead of a single range, and on the west by several detachtHl plateaus. Decided differences likewise* appear in the drainage of the two divisions, as well as in the forms of relief. On the nortli the di'ainage is eastwai-<l from the Alleghany Front, tlie (ii-eat Appalachian Valley, and the Blue Ridge, bj'' streams flowing directly to the Atlantic, or westward by New River to the Ohio. The line between the two divisions indicated above is approxi- mately on the divide south of New River, beyond which no streams break through the Blue Ridge towiu-d the east, iind oiilj- one, the Tennessee, escapes from the valley zone toward the west. It thus appears that the subdivision of the Appalachi- ans into a northern and a southern division is not arbitraiy, but is based upon broad physiographic diffei-ences between the two regions. These differences will api^ear more prominently ill the course of the detailed description of the Southern Ai>i)a- lachians.

(Copyright, 1895, by American Book Company.)

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The Southern Ai)palachiau Pi-ovince maj- be more exactly defiued as the rogiou lyiug southwest of a liue joiuiug the east- erumost point of Kentucky with Cape Fear, and hmited on the southeast, south, and west by the level plains which border the Atlantic, the Gulf, and the Mississippi. ^

PHYSIOGK.\PHIC' DmSIONS 0¥ THE SOUTHERN APPALACHIANS.

The region thus defined is not a simple physiographic unit, but is highlj- complex, and may be further subdi\-ided into five well-marked diWsions, each characteiized by the prevalence of a • listinct type of surface. The boundaries between these natural }>liysiographic divisions extend lengthwise of the province (that is, northeast and southwest), and they are therefore long, naiTow belts, with their sides approximately imrallel. Xamed in their order across the province from southeast to northwest, they are (1) the Piedmont Plain, (2) the Apjialachian Mountains, (3) the Appalachian Valley, (4) the Cumberland Plateaus, (5) the Interior Lowlands. The location, boundaries, and chief characteristics of these five divisions will first l)e given, followed later by a more detailed account of the three which more strictly constitute the Southern Appalachians.

(1) The Piedmont Plain extends along the southeastern base of the Appalachian Mountains. Its surface has a gentle east- ward slope from an altitude of about 1,000 feet at the western edge to 250 or 300 feet on the east, where the crystalline rocks of which it is chieiiy composed pass beneath the sands and clays of the Coastal Plain. The surface is not that of a smooth j)lain, for the I'ivers and creeks flowing across it have cut deep and rather narrow channels. They have etched and roughened a surface once much smoother than now. The western limit of the Piedmont Plain through North and South Carolina and a portion of Georgia is along an irregular hue, on which the gentle slope of the etched plain changes to the steep slopes of the Blue Ridge and its outliers, the eastern members of the Appalachian Mountain System. Farther south the western limit is not so well marked, for the surface of the mountain belt has been worn down almost as smooth as the plain itself.

(2) The Appalachian Mountains occu])y a narrow belt which extends northeastward from eastern Alabama, and swells out to

PHYSIOGK.U^HIC DIVISIONS. 309

its greatest width of about 70 miles in western North Carolina. This belt is not dominated liy a single mountain range, but is occupied by numerous groups of mountains of nearly equal mag- nitude. To the eastern members of this complex system, disre- garding a few groiips of outliers to be described later, the name " Blue Ridge " is generally applied. It carries the main divide I)etween the Atlantic and Gulf drainage southwest ward from the Roanoke in Virginia, across North Carolina, to the Chattooga and Tallulah rivers in South Carolina. The southeastern slopes of the Blue Ridge are exti'emely steep, forming an ii'regular escarp- ment toward the Piedmont Plain. The northwestern slopes, on the other hand, are usually gentle, with slight descent to the high valleys upon that side.

The northwestern edge of the mountain belt is marked by a range somewhat higher, but less continuous, than the Blue Ridge. This is called the Unaka Range. Toward the Virginia line it merges into the Blue Ridge, and thence sonthwestward diverges from the latter, terminating in northern Georgia. Between these two bounding ranges is a long, narrow, triangular area charac- terized by high valleys, above which rise many irregular moun- tain masses, most of their summits reaching a common plane between 4,000 and ."j,0()0 feet above sea level. The culminating point of the region is toward its northei'n end in the Black Mountains, one of which, Mitchell Peak, reaches an altitude of 6,711 feet.

(3) The Great Ai^palachian Valley consists of a long, narrow zone, whose surface is depressed several hundred feet below the highlands on either side. It is not a simple valley belonging to a single gi-eat river system, but is a structural belt within which the valley type of surface predominates. Its broad curves eon- form to the structural axes of the Appalachians; and their form, as well as the width of the valley, is quiti^ iii<lependent of the size of the stream which occupies it. Within tliis belt are many ele- vations rising from 800 to 1,800 feet al)ove its general level. The highest of these form a series of ridges along the southeastern side, of which Chilhowee Mountain may be regarded as the type. In other parts of the valley are long even-ci-ested ridges, of which Clinch ]\Iountain is the type, rising nearly to the level of the highlands on either side.

(4) The Cumberland Plateaus occupy the next belt beyond the Great Valley, their eastern escarpments rising abruptly along

310 THE SOUTHEllN APPALACHIANS.

its western side. They occupy a belt of country in which the plateau type predominates, extendingwith varyiugwidth, through eastern Kentucky and Tennessee and northern Georgia and Ala- bama, nearly to the Mississippi line. The belt reaches its great- est elevation in Kentucky, and has a gradual descent toward the south and west, finally merging into the Gulf Coastal Plain in central Alabama. The western limit of the belt is an extremely irregular escarpment, well marked in Alabama and Tennessee, but becoming indistinct in Kentucky.

(5) West of the Cumlierland Plateaus is a broad belt of coun- try forming a physiograx>liic division to which no distinctive name has hitherto been applied. It extends westward to the Tennessee and Ohio rivers, embracing the central basin and its highland lini in Tennessee, and the blue-grass region and western coal field of Kentucky. This region is essentially a plain of low relief, holding the same relations to the Cumber- land Plateaus that the Piedmont Plain does to the Appalachian Mountains. It is, in fact, a western Piedmont Plain. In order to avoid confusion, the region is here called the Interior Low- lands.

From the foregoing brief outline it is seen that the Southern Appalachian Province is composed of two elevated belts, — the Appalachian Mountains and the Cumberland Plateaus, — sepa- rated by a depressed zone, the Appalachian Valley ; while on either side are Piedmont Plains, — the Atlantic Piedmont on the southeast, and the Ohio Piedmont or Interior Lowlands on the northwest.

THE PROBLEM AND THE KACTOKS.

In order to appreciate the significance of these physiographic divisions, and to understand their origin, certain fundamental physiographic processes must be thoroughly understood. Al- though they have been explained at lengtli in an earlier mono- graph, those that are particularly applicable to this region will be briefly reviewed. It is also important that something should be known of the geology of the region — the composition of the rocks and their structural relations — in order to understand the conditions under which the physiographic forces work : hence a veiy brief outline of the geology wiU also be given before the several divisions are described.

PHYSIOGRAPHIC FACTOKS. 311

It must be liorne in iniud tliut everywhere on the earth's siir- facM:' where there is kind two grund pliysiographic processes ai'e going on, — the first dlastrophism, the elevation and depression of the land by forces acting from Ijeneatli ; and the second f/rada- tloH, the wearing-down of the land chictly by the action of run- ning water. Although the forces producing diastrophisin have sometimes elevated and at other times depressed the surface of the Appalachian Province, the elevations have been greater than the depressions, and the resultant effect has been a gain in alti- tude. The process of gradation also tends in some places to build up and in others to lowei- the surface of the land ; but the lowering liat< been far more common than the building ujj, so- that, on the whole, the effects of the two processes have been in op])osite directions. Diastrophism has lifted the land, and grada- tion has worn down its surface. At times the former proci'ss has gained upon the latter, and the region has had then a greater elevation ; at others gradation has been most active, and the sur- face has been worn down toward sea level. Thus the present altitude of the region is due to the balance between the two- gi-and physiographic processes, while the forms of the surface are due almost entii'ely to the character of the matei-ials on which the forces of gradation are at work. Dift'erences in the texture and structure are the principal causes of differences in the surface forms, and so of the physiographi(! divisions of the Appalachian Province outlined above. Tiie amount of elevation is an important but subordinate cause of present diffei-ences of surface.

A brief examination of the way in which the process of grada- tion is accomplished, and some account of the character and structure of the rocks in different portions of the Southern Appalachians, will make clear tlic origin of its physiographic subdivisions.

Physiogkaphic Factors. — The manner in which a river carves its valley has already been explained in a former monograph, — that on " Physiographic Processes," by IVIajor Powell, — and need be only bri(^tly referred to here. It was shown that when, through the action of diastrophie forces, a river finds itself flow- ing at a considerable altitude above the sea, its first work is to wear down its channel to near sea level by tlie process of rrrtiral corrasion; that when this is nearly accomplished, and its fall greatly lessened, it swings from side to side in ever-widening

:\V2 THE SOUTHEllN Arr.U.ACHUNS.

<urvos, and broadens its valley by the process of lateral cona- siiiii : and that the two are accompanied by a third process, that of erosion, by which the general surface of tlie country is worn down, its steep slopes smoothed out, and the material carried to the sea. These processes, if continued snflficiently long, reduce the surface to a low, level plain, — a hase-lcveled phiin if the jirocess is nearly complete, and a, peneplain if some ineqiaalities remain unreduced. Naturally it is seldom that a region is found in which the pi-ocess of gradation has just begun, or in which it lias reached completion in the prodiiction of a perfect plain. Most j)ortions of the earth's surface show the process in a more or less advanced stage. This is true of the Southern Appala- <*hian region, and the fonns of its surface ai'e such as character- ize various stages of the process. At each stage three factors are important in determining the details of the land surface in any region. These are (1) the chai'acter of the i-ocks considered with reference to their ability to resist erosion; {'!) the alterna- tion of hard and soft beds; and (3) the altitude of the beds with reference to a horizontal plane.

It is evident that soft rocks — i.e., those that are sohilile (as limestone), or which crumljle readily when exposed to the air (as calcareous shales) — will be worn down and carried away more rapidly than those which are composed of insoluble material, and are not affected by weathering (as quartzite and argillaceous slate). Hence, where the initial altitude is the same, areas undei'lain by tlic first class of rocks will l)e soonest reduced to base-level, and may form low level plains ; while the areas under- lain by hard rocks, although subjected to the same agencies of degradation for the same hmgth of time, remain above base-level as mountains or hills. Again, if beds of different character alter- nate, as beds of limestone with beds of quai'tzite, the latter are more readily broken down by imdermining and sapping than where the whole mass is composed of homogeneous, even though less resistant, material. Finally, if the beds are horizontal, they give a totally dift'ereut form to the smface (hiring gradation tlian if they are steeply inclined, especially if there is at the same time an alternation of hard and soft beds. Tn this case the streams first ciit narrow gorges bounded by cliffs which recede as already explained, the hard beds forming the escarpments of terraces, and the intervening soft beds forming their level tops or gentle slopes. If, on the other hand, the strata are steeply

(iEol-Odlf FACTOKS. 313

inclined, any i)articulai' hard bed quickly passes below the base- level of erosion. 'J'lie soft beds are rapidly worn down to this level, while ihc liard bed [jvojects as a narrow lidge or line of knobs.

While the altitude of the region, as stated above, is the re- sidtant of the two processes elevation and gradation, the manner in which the elevation took ])hice has exercised a controlling influence over the t()i)ograi)hic forms. In outlining the physio- graphic divisions, it was stated that no dominant range over- topped its iieighl)oi-s in either of the highland belts. On tiie contrary, in the Api)alachian ^Mountains, where such a dominant range might be looked foi-, the greater number of summits reach nearly to a common plane. If the present altitude of the region had been attained during a single period of elevation, either gradual or rapid, there would Ije nmch greater diversity in the height of different portions. The altitude of any part of the surface would then represent almost exactly the pr(»duct of two factors, — (1) the resistance of the material at that particular l)oint, and ('J) the nearness to main drainage lines. High points might be du(^ to relatively soft rocks, if favorably situated far from master streams, or to hard I'ocks not so situated ; while the highest points would result from a combiiuition of luirdest rocks and most favorable location. The absence of dominant peaks, then, taken in connection with other facts, indicates that the ♦'Icvation has not been accomplished in a single period, Imt has consisted of a series of comparatively rajjid movements, sepa- rated by long pei-iods of r(>st. During th<' latter the forces of gradation repeatedly wore down the surface to a more or less perfect plain. The soft rocks were protected below the base- level of erosion until anoth(>r ui)lift, while the hard rocks were 7'educed nearly, if not ciuitc, to that level: hence difference of rock texture was not permitt(Ml to exercise its full influence on the relief, but was kept within certain definite limits by the for- mation of siU'cessive peneplains.

(tEGLOGIC Factous. — The southeastern portion of the Appa- lachian Province — i.e., tli(> Piedmont Plain and a part of the mountain belt — has probalily l)eenalaud area since the earliest geologic periods of which we have record. The rocks are almost wholly crystalline, in part sediments which have been rendered <'rystalline by heat and pressure, and in part rocks which have <'ooled and crystallized from a molten condition. The former

314 THE SOUTHERN APPALACHIANS.

are called metanwrphic, aud the latter eruptive rocks; but they sometimes resemble each other so closely that it is uot always possible to distinguish them.

During all or the greater part of Paleozoic time the region to the northwest of the Appalachian Mountains was occupied by a sea in whidi sediments deiived from the old land to the south- east were being deposited. When er(.)si(.)n of the land was rapid, by reason of its gi-eat altitude, the streams carried down coarse material, sand and gravel, which was spiead over the sea bottom mostly near tlie shore, and now forms beds of sandstone and conglomerate. "\\Tien the old land had Ijeen partly worn down, the streams carried only fine sand and mud, which was more widely distributed ])y waves aud currents, and now appears as shale. Finally, when the surface was so far reduced that the streams became sluggish, they could carr}- only materials in solution, chiefly car])onates of lime and magnesia, which were deposited on tlie sea floor partly through the agency of animals, and jiartly as a chemical precipitate. Thus were formed the great beds of limestone and dolomite. All the beds thus laid do'svn were originally nearly horizontal, though uot entirely so ; for some parts of the sea bottom appear to have been depressed more than others, as though by the weight of sediment heapeil upon them.

Finally, near the close of Paleozoic time, the interior sea di- minished in size by the emergence of nuich of its bottom to form dry land. At the same time, tbe crust of the earth contracted, so that great wrinkles i-ose upon its surface as they do upon a withered apple. These wrinkles were not uniformly distributed, but were confined to narrow belts along certain lines, which ap- pear to have been lines of weakness, where the strata couhl be most easily bent and broken. In this manner the strata within a zone from 75 to 150 miles in width, stretching from New York to central Alabanui and an unknown distiince beyond, have been thrown into a series of long, luirrow, i)arallel folds. On the southeast is the original land area from which the interior sediments were derived, its crystalline rocks forming a massive buttress against which the sediments were tlirust and bent. To the northwest of the folded belt the strata stretch for many miles across the Mississippi Valley, with but little change from their original horizontal position. Tlie subdivisions of the Ap- palachian Province were thus determined long before the incep-

THE CUMBERLAND PLATEAUS. 315

tion of the sculpturing processes which have giveu to them their distinctive forms.

The mountain l)elt is the seaward portion of tlie old Paleozoic" continent from which the rocks to the westward were derived; the Great Valley is the landward portion of the Paleozoic sea in which the coarse sediments were mostly deposited, and to which the subsequent folding was mostly confined ; while the plateaus are composed of the offshore deposits, Avhich retain their original horizontal position.

DESCRIPTION OF THE PHYSIOGRAPHIC DIVISIONS.

Bearing in mind the princii)l('s of physiography outlined above, and the differences in geologic structure, we are now pre- pared to examine more in detail the forms of relief of the vari- ous subdivisions of the Southern Appalachians, and to trace the cotmection between structure and topographi(! form. Only the two belts of highland, with the intervening valley, will be con- sidered ; the Piedmont Plain and the Interior Lowlands lying beyond the scope of this paper.

The Cumberland Plateaus. — The western of these three divisions, the Cumberland Plateau, will be taken up first, since it presents the simplest pliysiographie eontlitious. The rocks which form the surface in this region are of Carboniferous age, and consist of sandstones, shales, and limestones. The lime- stones lie beneath the sandstones, while the beds of shale alter- nate with beds of sandstone, and all tlu^ strata are nearly hori- zontal. The limestone is degraded eliiefly by solution ; while the sandstone is insoluble, and can be worn chnvn most readily by undermining and sapping. As soon, therefore, as the streams by vertical corrasion have cut through the sandstones and shales into the underlying limestone, they are bounded by cliffs, and the degradation of the entire region is effected chiefly by their recession. The slopes are kept steep by the more rapid removal of the lower limestone than of the upper sandstone beds. The beds of sandstone form steep, often vertical edges of terraces, while the intervening beds of shale form their more or less gently sloping surfaces. It is chiefly in the central portion that the plateau character is well marked. In northern Georgia and Ala- bama and the adjacent portions of Tennessee the conditions are

31G * THE SOUTHERN A1'1'AI.\( 111 AXS.

favorable for the ilevelopnieut ami in-isisit'iice of steep esrai-p- jiu'Uts bouiidiiijr level plateaus. Fartlier south the base of tlie samlstoue is so low that the streams d<> not reaeh the limestone, and hence the process of sapping, l)y whicli the cliffs recede while retaining their steep slopes, is not favored. The same is true in eastern Kentucky and the adjacent i)ortions of Tennessee. Also in the latter regions the sandstones are nearly honutgeneous, and do not afford the strong contrasts between altciiuiting licds Avhich are favorable for the formation of cliffs: lu'iice the slopes, althoiigh steep, are smooth from top to bottom, and the region is cut into hills with siiarii or rounded summits.

The opposite sides of the plateau are formetl by abi-ui>t escarp- ments. That on the east, fronting upon the Appalachian X'allcy, is generally straight or broadly curved, except for a single abrujit bend which it makes north of the Emory Ki ver. Here the escarp- nuMit turns from its northeast course sharply toward the north- west for a few miles, and then resumes its former direction. The western escarpment, on the other hand, is extremely irregular. Streams flowing westward from the plateau have cut deep reen- trant angles far within its edge, leaving many narrow spurs pro- jecting into the lowland beyond. This difference between the escarpment on opposite sides of the plateau is due chiefly to the attitude of the underlying rocks. Toward the Avest the strata extend for a long distance nearly horizontal. The highland has been converted into lowland by erosion of the face of the escarp- ment liy the process of cliff" recession already described ; and this recession has been irregular, — most rapid where the streams could l)ear away the debris from the base of the cliff's, and least ra])id far from the larger streams, where the transporting power of the water was small : hence the deeply rei'utrant coves and the strongly salient spurs. The form of the eastern escarpment, on the other hand, does not depend on the accidents of cliff reces- sion, for the recession is controlled by the attitude of the strata. As already indicated, the region east of the ])latean is cliarac- tenzed by steeply inclined strata. The folding which they have sutt'ert^d has brought underlying soft limestones and shales high above the base-level of erosion, where they were attacked and worn away. At the present escarpment the strata dip steeply to the westward, carrying the soft I'ocks below the base-level, and presenting a barrier of hard rocks beyond which erosi,ou has not yet been able to go: in other words,

TH1-: Ari'ALAtlllAN VALLEY. 'All

the position of the escarpmeut depends on the position of the westernmost of tlie steejj folds ehavacteriziug the Appalachian \'alley belt.

From the Emory River southward to the Tennessee at Chat- tanooga, the eastern boundary of the plateau is a linear escarp- ment ; but twelve miles to the west is a narrow valley, jierfectly straight, and also bounded by parallel linear escarpments. Tiiis is Sequatchie Valley. Its position and form are directly depend- ent upon a narrow anticlinal fold, which extends i)arallel with t lie folds in the belt to the eastward, and which lifted the plateau sandstone so far above base-level that it was easily removed, ex- posing the underlying soft limestone to erosion. The process Ijy which this linear valley was formed is still going on at the north- ern enil of the anticline, whei-e the ai'chiiig strata are not yet wholly removed. They form the Crab Orchard Mountains, which extend northward directly in line with the Sequatchie Valley. Wherever the protecting cai:> of sandstone has been rejnoved, deep coves are formed in the underlying limestone. These are often surrounded by a lim of sandstone, and the water collecting in them flows off through subterranean ]tassages which it has formed by the solution of tlie limestone.

From the southern border of Tennessee, southward well into AlaV)ama, the plateau is separated into three or more nari'ow strips by parallel anticlinal valleys, one of them tlie continuation of Sequatchie Valley, an<l tlu* others formed in exactly the same manner. The easternmost of these narrow plateaus is Lookout j\[ountain, which terminates in a high alirupt jtoint at Chatta- nooga. Southward from this 2)oint the mountain widens slightly, and towtird the southern end changes its form from a level- topped i)lateau to a shallow trough, the pai-allel escai'pments passing into monoclinal ridges, which terminate abriiptly in Alabama at Gadsden and Attalla. West of Lookout Mountain, and separated from it by Lookout and Wills valleys, is Sand Mountain, the soxithward continuation of Walden Plateau, and, like it, bounded by parallel linc^ir escai'pments. Bej'^ond Sand Mountain is the Cumberland Plateau proper, in northern Ala- bama, so deeply dissected that only isolat(Ml mesas remain, but south of the Tennessee River forming a bi-oad table-land sloping gently southward.

The Appalachlvn Valley. — As already stated, the Great Aji- palachian Valley is located u]ion a licit of intensely folded strata,

318 THE SUITHEKX APPALACHUNS.

and to the structure and character of the rocks it directly owes its characteristic features. Its several portions are occupied by ilistiuct river systems, and the position and form of the valley are independent of the position and size of the streams it bears. The valley has a width of about 45 miles in northern Georgia and Alabama, 50 miles opposite the broadest portion of the Appala- chian Mountains, expanding to 65 miles in northern Tennessee, and contracting to 30 miles in southern Virginia. The western side of the valley is formed by the plateau escarpment rising abruptly from 800 to 1,500 feet, its summit everywhere present- ing an almost perfectly straight horizon. East of the Great Val- ley rise the Unakas, their .sharp or rounded summits forming a sky line totally different from that to the west.

To one traversing this region l)y rail its true character is not apparent. He sees innumerable hills and ridges of varying lieights inclosing broad or narrow valleys, according to the size of the stream. The limiting highlands are generally hidden by the nearer elevations, and it is seldom that both can be seen at the same time. If, however, the observer ascends to the high- land on either side, the hills and ridges which give character to the country as seen from below appear only as minor inequalities of the surface. Tlie region is essentially a broad plain within whose surfaces the streams have carved their valleys from 50 to :500 feet.

The ridges which occur in various portions of the valley belt may be classified in three groups. In the first are those which approach in altitude the plateau escarpments and the high val- leys of the Appalachian Mountains. To this class belong Clinch, Bays, and White Oak mountains, in Tennessee; and Taylor.s, Chattooga, Gaylor, Dirtseller, and Cohin mountains, in Georgia and Alabama. These are all narrow ridges, some of them of great length, extending parallel with the sides of the valley belt. Their crests are almost perfectly horizontal, making an even sky line like the plateau escarpment. These ridges are formed by a liard bed of Silmian sandstone of uniform thickness, which usu- ally dips steeply to the east. Soft beds above and below have been worn down, lea^-ing the hard one projecting as a ridge. The reason for this uniform altitude and these even crests will be given later.

The t^-pe of the second class of valley ridges is the Chilhowee Range, which lies along the western base of the more massive

THE BLUE RIDGE. 319

Unakas. It includes Holston, Irou, Euglish, Chilhowee, Starrs, and Beans mountains, in Tennessee ; and Indian, Weisner, Cho<'- colocro, and Terrapin mountains, in Alabama. These differ from the Chnch Mountain tyj)o in their greater altitude and less regular crests. They are due to massive beds of Cambiian quartzite, which is more resistant than the Silurian sandstone, and hence produces higher ridges; but, on tlie other hand, it is less uniform in thickness, so that the resulting ridges have less even crests.

The third class includes the very large number of low eleva- tions that make up the minor irregularities of the surface, — broad rounded hills, sharp knobs, and narrow ridges, rising from 100 to :!00 feet aljove the streams. Their foi-m is dependent cliiefly on the character of the material, the degree of relief, or the near- ness to the main di'ainage lines. Seen from an elevation at the edge of the valley, these minor irregularities appear as a series of green billows, all reaching nearly the same level, above which rise, like islands, ridges of the Clinch and Chilhowee tyi^es: in other words, the elevations of this class reach a common plane, above which rise the larger lidges and highlands, and below wliich the present valleys of the streams nn.', sunk. The signifi- cance of this plane will be pointed out later.

The Appalachian Mountains. — Having briefly described the topography of the adjoining physiogi'aphic districts, the main Appalachian Mountain belt will be next taken up. Some of its more prominent features have already been outlined, and will now be considered in greater detail.

The belt is not a unit dominated by a single range or gi'oup of mountains, but is complex, containing several elements of nearly equal importance. These are (1) the Blue Ridge, ("2) the Eastern Monadnocks and Piedmont Valleys, (3) the Unaka Kange, (4) the Central Mountain Groups and Intermontane Valleys.

The Blue Ridfie. — The Blue Ridge, carrying the nniin divide between the Atlantic and (luif drainage, is everywhere nearer the eastern than the western side of the mountain belt; and, neglect- ing a few groups of outlying mountains whose mass is insignifi- cant compared with those west of the divide, the Blue Ridge may be regarded as fornung the extreme eastern range of the Api)ala- chian Mountains. It reaches its greatest height in (xrandfather Mountain, with an altitude of 5,964 feet. Thre(> other points reach above 5,000 feet; and a dozen or mor(\ most of them in

3'JO THK SOVIHEUN APP.VL.UHIAXS.

North Carolina, above 4,U00 feet. The gaps show a somewhat regular decrease iu altitude on either side of the cuhiiiuating point, from 4,000 feet iu the vicinity of Grandfather Mountain, to '2,'200 feet near the South Carohna line, and 2,700 at the Vir- ginia line.

The most striking characteristic of the Blue Ridge is the gi-eat difference in slope on its opposite sides. The streams heading in the gaps upon the di\'ide flow westward in broad, smoothly rounded, and drift-filled valleys for many miles before entering the naiTOw rock-cut gorges of their lower coiu'ses. Tliose flow- ing eastward, on the other hand, plunge immediately do^^^lward iu a series of cascades, falling several thousand feet in a few miles. They have no valleys, only V-shaped gorges until they reach nearly to the level of the Piedmont Plain. This difference in slope is adniiiably shown on the Southern Railway from Ashe- ville to Salisljury, N.C. From Asheville eastward, the road as- cends the valley of the Swanuanoa with an easy grade, making directly for the gap. Passing the di\dde, it descends upon the head waters of the Catawba by an intricate series of loops, wind- ing back and forth upon the mountain side in such a way that at one point three tracks can be seen one above another, and a descent of 1,100 feet is accomplished between points only ;> miles apart in an air line. Reaching the level of the Catawba at an altitude of 1,400 feet, the road again follows a broad valley with easy gi-ade down to the Piedmont Plain, which it reaches 50 miles to the eastward, at an elevation of 1,000 feet. Northward from the Virginia-North Carolina line — that is, in the Northern Appalachians — the Blue Ridge presents a comparatively smooth and regular face toward the east ; and as far as the Roanoke River the divide is upon the extromo eastern edge of the mountain belt. Southward in North Carolina the divide is usually some distance from the edge of the belt, and many long spurs extend from the main ridge toward the south and soiitheast. They are separated by deep vaUeys, which often broaden into coves shut in by steep mountain walls. The most extensive of these spurs are at the head waters of the Yadkin and Catawba rivers, in the central ])ai-t of western North Carolina. The eastward-flowing streams liave cut back into the mountain belt, and, haA-ing the advan- tage of a more direct course to the sea, have encroached upon the territory of westward-flowing streams, — the New, Watauga, Noliehucky, and French Broad rivers, — and have robbed them

MONADNOCKS AND PIEDMONT VALLEYS. 321

of portions of their drainage basins. Thus the Lin\dlle River, a northern tributary of the Catawba, has cut through the Blue Ridge proper, so that the hitter forms a spur extending south- ward from Grandfather Mountain for 20 miles, the divide being on a less elevated ridge, parallel ^vith it, and a few mUes to the west.

The Blue Ridge, bearing the main divide, has a direct south- westerly course, with only minor deviations, across North Caro- lina. At the South Carolina line the divide turns abruptly to the northwest, making two Iwoad loops which inclose the basins of the Chattooga and Tallulah rivers. South of the latter the divide returns to its former southwesterly course along the southeastern side of the Chattulioochce River. The Blue Ridge itself, though not followed by the main divide, continues south- westward across the corner of South Carolina as the Chattooga Ridge, and beyond the Chattooga River into Georgia as the ( 'hattahoocliee Ridge. Th(» latter, at no point more than 1,600 feet in altitude, gradually merges into the Piedmont Plain before reaching Atlanta.

The Eastern Mntiadnocks and Piedmont Vallei/s. — In addition to the spurs from the Blue Ridge mentioned above, there are several groups of mountains along the extreme eastern border of the mountain belt, which have been more or less completely isolated by the erosion of eastward-flowing streams. The most important are the Brushy, South, and Saluda mountains. The iirst-named group lies between the Yadkin and Catawba rivers, extending for 50 miles nearly parallel with the Blue Ridge, and l)etweeu 15 and 25 miles distant from the main divide. The liighest points reach an altitude of 2,700 feet, while the gap between this gi-oup and the Blue Ridge is only 1,300.

South of the Catawba River are the South Mountains, which extend for 50 miles nearly east and west, their axis making a large angle with the Blue Ridge divide. A few points reacli an altitude of 3,000 feet, or about 1,800 feet above the level of the (Catawba and Broad rivei- valleys.

Tlie third gi'oup, the Saluda Mountains, also trend nearly east and west, their crest forming the boundary between North and Soutli Carolina for about 20 miles. They are liiglier than the others described, reaching 3,100 feet, but are much less com- ])letely isolated, and may be considered as a spur from the Blue Ridge.

322 THE SOUTHEKN APPALACHIANS.

These three mouutain groups are isolated from the Blue Ridge and from one another by the Yadkin, Catawba, and Broad river valleys. The latter are simply portions of the Piedmont Plain, with which they are continuous toward the east. They may be regarded as bays projecting westward from that plain between headlands formed by the mountain groui)s.

All of these groups are deeply dissected by ei'osion. Although once massive continuous ranges, they are now cut by deep ti'ansverse valleys into manj" short ridges and peaks. Their altitude decreases toward the east, and thej^ give place in that direction to isolated knobs entirely surrounded by the Piedmont Plain.

It is evident that these outlying groups form an integral part of the Appalachian Mountain system. The main divide was formerly far to the east of its pi'esent position, but it is slowly migrating westward. The Atlantic di'ainage has the great advan- tage of a much shorter course to the sea, and hence steadily en- croaches upon the territory of streams flowing westward. TJjc Catawba, Yadkin, and Broad rivers have pushed the divide west- ward, and reduced the immediately adjacent conquered territory- to the level of the Piedmont Plain, which v;ntil very recently was the base-level of erosion. The regions between these streams they have not yet had sufficient time to reduce completely, so that groups of mountains there remain which are the I'esiduals of a former continuous highland: in other words, they are Monadnocks more or less typically developed.

In cases of recent capture, the stream valleys remain nearly at the elevation of the l)eheaded stream. Thus the upper por- tion of the Linville Valley has an altitude above 3,800 feet; and the stream, after flowing for 10 miles in a broad open valley, plunges into a narrow gorge with a fall of 1,000 feet in less than 3 miles. The upper valley of the Catawba, on the other hand, is below 1,500 feet, and oidy the smallest tril)utaries have rapid fall. In the lattei' case the conquered territoiy' is thoroughly subjected; in the former the capture has been recent, and the reduction is not complete.

The Uriaka lianqr. — The Unaka Range forms the northwest- ern member of the Southern Appalachian Mountains through- out the greater part of their extent. It does not form a continu- ous divide, as the Blue Ridge, but is cut through by numerous streams. From the Doe River northeastward the ranges fronting

CENTKAL MOUNTAIN GROUPS. 323

upon the Appalachian Vallej^ are long straight ridges with few lateral spurs ; that is, they closely resemble the valley ridges al- ready described. Although they are to be regarded as members of the mountain belt, since there is no lowland between them and the Blue Ridge, they differ materially from the* Unakas. The latter may be considered as terminating between the Doe and Nolichucky rivers. Thence southwestward the range is fairly continuous for 200 miles to northern (Jeorgia, although its dif- ferent portions bear many local names.

As already stated, the highest point in the Blue Ridge, and the one reaching an altitude approaching f),0()() feet, is Grand- father Mountain. From this point, in whicli the Blue Ridge au<l the Unakas may be regarded as uniting, an irr(^gular mountain range extends nearly due west GO miles to Paint Rock on the French Broad River. This is the northern division of the Una- kas. East of the Nolichucky it embraces Haw, Roan, and Unaka mountains; and between the Nolichucky and French Broad, th(? Bald, Big Butt, and Cow Bell niovintains. Beyond the French Broad the range has greater unity, and reaches its tyjiical devel- opment in the Great Smoky Mountains, which form a massive chain, continuous, except for Big Pigeon Gorge, for 75 mUes to the Little Tennessee River. Beyond this the range is made up of smaller groups, separated by frequent river gorges. It includes the Sassafras, Unaka, Frog, and Cohutta mountains, terminating with the latter group in northei'n Georgia.

Compared with the Blue Ridge, the Unaka Range reaches a considerably greater average altitude, and contains most of the higher peaks in the Southern Appalachians. While the Blue Ridge contains only 4 points above 5,000 feet in altitude, the Unakas have 18 or more above 5,000 ; and of these, 8 are above (5,000. Not only have they gi-eater altitude, but their slopes are steeper, and their outlines more angular and rugged. The Blue Ridge is generally steep only on the southeastern side, while the Unakas are equally steep on both sides, and slopes ^^^th a descent from crest to stream of 4,000 feet are not uncommon. Many liigh spurs leave the central chain, and between them are deep V-shaped ravines.

The Central Moirntain Groups and Itdcrmontane VaUcjiti. — From any commanding point along the Unaka Range there may be seen stretching to the east and south a great sea of peaks, ridges, and domes. There is no dominating range, but most of

J24 IHK SOI riii;i;\ Arr.vL.uiUANs.

the peaks reai'h nearly tlic same altitude, and aiipcar like the waves OH a elioppy sea, rauge after range growing less aud less ilistiiict, until their outlines are barely distinguishalile from tlie l)hu' sky at the horizon.

These are the niouutaiu gi'oups which occupy the central por- tion of the belt or basin ]>etweeu the outer ranges. The culti- vated valleys are generallj- hidden from view, and except for an occasional clearing on the mountain sides, and the grassy " balds " on a few of the higher domes, the whole region appears to 1)e covered with a forest mantle. Only i-arely does a ledge of naked rock appear through the vegetation ; so that the slopes are smoothed aud softened, aud the landscape lacks the rugged chai-acter of uuforested mountain regions. The atmospheric effects also tend to produce the same result. The blue haze which is almost never absent from this I'egion, aud which is rec- ognized in the names of both the Blue Kidge and the Great Smoky Mountains, softens the details of objects comparatively near at hand, and gives the effect of great tlistance to peaks but a few miles away. By reason of this atmospheric effect these mountains of only moderate altitude often afford more impres- ,sive views than heights aud distances two or three times as great in the clear air of the West.

Some of these interior groups are njore or less isolated, but most of them are in some degree connected with one or the other of the ranges which rim the basin. They generally have the form of short i-anges from 5 to 20 miles iu length, carrying a number of peaks a few hundred feet above the iuterveuing gaps, and sending off" long spurs which may themselves have peaks as high as the main ranges. There is no uuiformitj' iu their treiul, although iu most cases it is across the axis of the mountain belt rather thau parallel A\ith it. A very large number of the interior summits reach altitudes between 4,000 aud 5,000 feet, aud a few are over 6,000. The Black Mountains, a few miles north of Ashe- ville, contain the highest peaks in the Appalachian Mountains. Mount ]\Iitcliell, with an altitude of (5,711 feet, is the highest point east of the Mississippi, being 425 feet higher than Mount Washington.

Between these groui:)s, aud forming a sort of platform above which they arise, are many broad valleys, commonest toward the lieads of the streams, aud hence iu the southeastern side of the basin; that is, along the northwestern base of the Blue Ridge.

IMEKMUNTANE VAULEYS. 325

Only the smaller streams are still flowiiij;' at the level of these valleys. Followed downstream toward the northwest, the broad valleys are found to be more and more deejtly eut, until finally all trace of tiiem is lost, and the streams are found in deej) nar- row gorges. These gorges in which the streams in their lower courses flow are being cut backward into the valleys at their head waters: hence the broad valleys were evidently formed under conditions different from tliose prevailing at the present time. They must have lieen formed near sea level, when their streams had cut down to l)ase-level, and were widening their channels by latei'al corrasion. The presence of these high valleys is the best possible evi<Ience that the altitude of the region in which they are found has been increastMl by elevation in com- ))aratively recent times.

The characteristics of these iutermontane valleys are admi- rably displayed in the vicinity of Asheville, N.C. Seen from an altitude of about 2,200 feet, the region appears as a broad level plain, stretching in all directions to the ])ase of the smTounding mountains, which rise from it with abrupt slopes. The same plain with slight rise extends far up the Swannanoa and French Broad rivers, and up the smaller streams among the }nountain spurs. At Asheville the river has cut a channel a little more than 200 feet deep within this plain, and this channel increases rapidly in depth toward the northwest, in which direction tlie river and its trilnitary streams have deejjly dissected the i)lain. Its remnants, however, still reach a common level, so that it can be easily reconsti-ucted. Eastward on the Swannanoa, and south- ward on the French Broad, the plain is less and less dissected, and toward the head waters of these streams the broad valleys are almost perfectly preserved. These iutermontane valleys ar(i found on all the northwestward-flowing streams of the mountain belt; but they increase in extent, and at the same time dtM'rease in altitude, toward the southwest. On the French Broad the altitude of the valley is about 2,200 feet ; on the Little Tennessee, 2,000; on the ujiper lliwassee, 1,800; on the Ocoee, 1,700; on the Coosawattee, 1,500 ; on the Etowah, 1,100 ; and on the Tallapoosa, 1,000. They ai)pear on the first three of the above-named streams as des<'ribed on the French Broad, — level a ivnas, walled in upon all sides by the encircling mountains, with a narrow gateway leading westward through the Unakas to the Gi'eat Valley. Southward from the Hiwassee, the adjacent valleys

326 THli SOITHEKN APPALACHIANS.

merge with low divides, and the niouutain groups are more completely isolated. Still further south, on the Etowah and Tallapoosa, the valleys are so broadly d<'veloped that the divides separating adjacent basins are scarcely pei'ceptible, and the only mountains remaining are isolated, island-like Monadnocks. Ex- cellent examples of the latter are seen in Kennesaw and Lost mountains, in northern CJcorgia. From a distance of a few miles they appear as smooth oval domes, rising with symmetrical slopes above a level plain. This plain is slightly etched by the present stream channels, which are from 50 to 150 feet in depth, but on the horizon it makes a i)eifectly even sky line. It ex- tends entirely across the mountain belt from the Great Vallej- to the Piedmont Plain, southwest from the vicinity of Marietta to the Alabama line, iutei'vupted only by a few low Monadnocks. In Alabama it is less perfectly developed, and the interrupted Appalachian Mountains reappear in the Talladega Eange. The latter forms a narrow mountain group 50 miles in length, con- sisting of a high central ridge bordered by low hills. It should properly be considered the southern member of the Unakas, al- though separated from the main range by an interval of nearly 100 miles.

Dependence of Surface Forms on the Ch.\eacter of the KocKS IN THE Mountain Belt. — It was shown in a preceding part of this monograjih that the physiography of the Cumber- land Plateau and of the Great Appalachian Valley Avas most in- timately connected with the character and attitude of the rocks underlying those regions. It was there shown that horizontal beds of varying hardness are carved by streams into plateaus; and that the same beds, when tilted, produce long, narrow ridges. In like manner the form of the surface in the moun- tain belt is in large measure dependent on the character of the underlying rocks, although its greater altitude is due in part to recent uplift.

In their behavior toward the agents of erosion, the rocks of this region differ from those toward the west chiefly in being more homogeneous. They consist in part of crystalline rocks which have solidified from a molten state, as granite and diorite, with crystalline schists derived from them; and in part of slates and conglomerates, sedimentary rocks, which have been more or less altered by heat and ])ressure. Excepting a few beds of marble, limestones are entirely wanting. The original differ-

DRAINAGE. 327

«nces in harduess between such sedimentary beds as shale and conglomerate have been nearly obliterated by subsequent changes which tliey have uiidei-gone, so that they present nearly the same degree of resistance to the agents of erosion. For this reason the mountain ranges do not generally conform in trend to the strike of the rocks ; while there is a very uniform northeast strike within the mountain belt, the crests of the interior ranges in particular are extremely irregular, and tlie long spurs are quite as apt to cut across the stioke as to fol- low it.

Some differences in the underlying rocks, however, find ex- pression in slight differences in the topographic forms. Thus the southeastern portion of the mountain belt is occupied almost exclusively by crystalline rocks, and these generally give rise to broad and massive domes with smooth contours. Such forms characterize the Blue Ridge and adjacent mountain groups. The northwestern portion of the l:)elt, on the other hand, is occupied chiefly by metamorphic rocks. These yield less i-eadily to dis- integration than the wholly crystalline rocks : hence the gi'eater altitude of the Unaka Range, and the prevalence there of shai'p peaks rather than of rounded domes.

DRAINAGE OF THE SOUTHERN APPALACHIANS.

The streams of the Southern Appalachians have already been frequently mentioned in the foregoing physiographic description of the region, but the drainage requires a few words of further explanation.

The waters falling ujion various parts of the region find their way either eastward to the Atlantic, southward directly to the (xuK of Mexico, or to the Mississippi and thence to the Gulf. The divide between the Atlantic and Grulf drainage follows the crest of the Blue Ridge, as already described, from the Roanoke south westward. The eastward-flowing streams are pressing this divide gi-adually westward by the capture of territory from less favorably situated streams west of the divide. Cases of recent capture are seen at the head of the Linden and Tallulah rivers, the falls on those streams showing that the newly acquired ter- ritory has not yet been in their possession sufficiently long to be ■completely su1)dued. Northwest of the divide the streams flow

328 THE SOUTHERN APPALACHIANS.

at first in the high valleys, many of which were evidently formeil by larger streams than those now oerupying them. Leaving the Blue Ridge, with its gentle slopes and low gaps, thej'flow north- westward in deepening channels, directly toward the higher and more rugged Unakas, which they cut through in narrow gorges. Emerging upon the Appalachian Valley, those south of Kew River are intercepted by triuik streams, and led oft" toward tiie southwest. From New River to the (leorgia line the trunk stream is the Tennessee, which leaves its southeastward course and at the same time the broad Apijalachiau Valley by an abriipt bend at Chattanooga, traversing the Cumberland Plateau in a narrow gorge evidently much younger than other portions of its valley. Southward from the Georgia line the tritnk stream is the Coosa, which flows directly to the Gulf, following the axis of the Great Valley.

The divide between the Tennessee system and streams flow- ing directly to the Gulf leaves the Blue Ridge in northern Georgia, and follows an irregular line toward the west, crossing successively the mountain l)elt, the Great Valley, and the pla- teaus. It is peculiar in not following the crest of a ridge for any distance, but in cutting across ridges and vallej's marked in many places by a barely perceptible rise of the land. There is evidence that this diA'ide, like the gorge of the Tennessee through the plateau, is extremely young; that until comparatively recent times all the waters flowing west from the Blue Ridge found their way directly to the Gulf across the present Tennessee-Coosa divide.

The stream courses within the valley belt show a close ad- justment to the structure of the region. In general they are located upon belts of soft rocks; and when they leave these, they always cross intervening hard beds by the most direct course at I'ight angles to the strike. They more often occupy the axes of anticlines than of synclines, so that they nnist have migrated to their present locations by the process of stream adjustment outlined by Mr. Willis in Monograph No. 6.

PHYSIOGRAPHIC DEVELOPMENT OF THE SOUTHERN APPALACHIANS.

Having before us the main physiographic features of the Southern Appalachian region, we are prepared to follow an out-

PHYSIOGRAPHIC DEVELOPMENT. :]L'i)

Hue of the history of its development. Its earlier history, wliile the region was in part, at least, covered by the sea, is read in the sedimentary rocks ; while the later chapters, covering the i)eriods during which it has been dry land, are inscribed in the tonus of the land surface and the relations of its streams.

Studying the rocks of the three western divisions of the jirov- iuce, we know that the sediments of which they were oomijosed were derived largely from laud lying toward the southeast, prob- ably in the region now occupied by the Piedmont Plain and beyond. In very early times the sea may have covered what is now the Blue Ridge; but, if so, the shore line was early pushed toward the northwest, uncovering to erosion the present moun- tain l)elt, which furnished much of the material foi- the later sedimentary rocks. For a long tinu3 the sea margin was near the northwestern side of the mountain belt, oscillating within narrow limits, but gradually nngrating westward. Sometiiing can be learned, from the sedimentai-y rocks thus laid down, of the old land area from which their nuiterials were derived. Thus conglomerates indicate steep slopes and I'apid streams, while limestones point to the opposite extreme, — a land with low relief and sluggish streams, able to supply but litth* irag- meutal material to the adjoining sea. At least two great cycles of erosion are thus recorded in which the surface of the old con- tinent was worn down from a consideralde altitude nearly to base-level.

Shortly after the close of the Carboniferous period thcf entire Southern Appalachian Province was finally lifted above sea level, and its subsequent history is recorded chielly in laiul forms. At the same time that the region was elevated, the strata in a long narrow belt adjacent to the old shore line w(>re in- tensely folded. The streams flowing from the old land into the interior sea before the emergence doubtless continued in the same direction, extending their lowei' courses across the newly added laud as successive belts emerged. Since the process of folding was exceedingly slow, they may have held their original courses for a long time in spite of the folds rising across tiieir path. These folds, however, although not directly able to turn the rivers aside, l)i-oiight bands of soft rocks above base-level, aiid so were able indirectly to accomplish that result. Streams flowing southward parallel with the folds were located entirely upon soft rocks, and so were able to deepen their channels luoi-e

:;oU IHK SUirUEKN APPAIACUUNS.

rai>itlly tliau those tlovviug westward across iiiauy hard beds: liciK-e the streams iiarallel with the folds encroached iipou the territory of tlie transverse streams, aud successively captured them, and led them by southwestward com'ses directly to the (lulf. When once fairly started, the couqiiest proceeded rapidly toward the northeast; but, before it had reached NewEiver, the latter had been able to sink its own channel so deei)ly that the Holston could not cut through its banks and divert it. It intrenched itself successfidly against the encroachments of its marauding neighbor. New River therefore continues north- westward from its sovu'ce on the Blue Ridge, across the moun- tain belt, the Great Valley, and the Cumberland Plateau. It is the only stream in the entire Ai)palachian Pro^dnce which retains throughout its eutii"e length approximately its original position.

Following this uplift was a long period during which the region was subjected to the physiographic processes constituting gradation. These have been described in preceding monographs. Probably base-leveling was several times carried nearly to com- pletion during this jteriod; but the peneplains thus formed were destroyed by subsequent erosion, and no record of them i-emains. Finally, toward the close of Cretaceous time, the whole province was reduced to a nearly featureless plain, re- lieved only by a few groups of jNIonadnocks whei'e the highest Tiioiintains now stand.

After the process of base-leveling was nearly completed — that is, toward the close of the Cretaceous — the region was again lifted, but unequally, so that at the same time its sm-face was warped. The streams had become sluggish, but the effect of the uplift was to stimidate them to renewed acti\'ity. They began at once to lower their channels in the old peneplain, and, when thej^ had reached the new base-level, to form a new pene- plain by lateral corrasion. This process went on most ra^iidly on areas underlain by easily erodible rocks; so that the ne^v {)eneplain was extensively developed on the limestones of the valley l)elt, while the streams still flowed approximately at the old level on tlie hard sandstones of the plateau and the slates of the mountain belt. It is from these remnants preserved upon areas of hard rocks that we are able to reconstruct the older peneplain. The largest remnants are seen in the smooth, even summits of the Cumberland Plateau. It is also preserved in the

KELATION OF UECENT UPLIFT AND PRESENT ALTITUDE. 331

even crests of the valley ridges, ;iii<l tlu; high valleys witliiu the mouutiiin belt.

The formation of the second peneplain was well advanced over areas of soft rocks, when the region was again sul>jected to a series of verti(!al oscillations, th<^ final result of which was ele- vation accompanied by warping. As before, the effect of the elevation was to stimulate the streams so that they began cutting upon the last-formed penei)lain, — a process in which they are still engaged.

During the last series of oscillations mentioned above, some important changes were produced in the drainage. Previous to this the waters of the valley belt from New Kiver southwestward had collected into a single trunk stream, which flowed aci'oss the present divide directly to tlie (lulf liy tlu* ]tresent course of the Coosa River. A peculiar set of conditions for a time gave suffi- cient advantage to a westward-flowing stream to enable it to cut through the jjlateau, and divert the trunk stream westward to the present coiirse of the Tennessee.

RELATION OF KKCENT UPLIFT AND PRESENT ALTITUDE.

It was shown in describing the Appalachian Mountains that from the culminating point in North Carolina the average al- titude of the belt decreases southwestward; that the bounding ranges, the Blue Ridge and Uuakas, as well as the interior moun- tain groups, become less massive and more deeply cut by trans- verse (h'ainage chainiels ; and that the intermoutaue valleys, which in the northern part of the belt ai-e walled in by moun- tains upon all sides, occupy an increasing proportion of the area, until in Georgia they form a level plateau stretching entirely across the belt, and intei-rupted only by a few isolated IMonad- nocks. The cause of this gradual decrease in altitude toward the southwest can now be understood. It is not due to tlie ]ii-(»s- enee of more easily erodible rocks in the southern than in the northern portion of the belt; for they are essentially the same kinds, and, in their unweathered condition, offer tho sam<' degree of resistance to agents of gradation. The cause is rather in the different amounts of uplift which the two regions have suffered in recent geologic periods. It was stated above that the Soutli- ern Appalachinns had been several times more or less comjiletely base-leveled, and that each base-leveling period was followed l)y

33-2 THE SOl'THEKN" ArrAl.ACIllANS.

an uplift -which stimuhited the streams to renewed activity upon the peneplain. It is evident that the depth of tlie gorges cut by the rejuvenated streams would depend on tlie amount of the up- lift ; and hence the height of the mountains, which are simply remnants of the deeply dissected peneplain, would also dej^end on the amomit of u^dift. In regions whore tlie uplift was great, the intervening portions of the peneplain would long remain as high mountain masses ; and, on the other hand, where the uplift was slight, the streams would quickly cut down to the new base-level, and begin the task of removing the interven- ing highlands: hence moderate iiplift would not only give rise to low mountains, but would favor the formation of isolated Mouadnocks.

Again, during the later stages of the base-leveling process, the rocks of a region became deeply weathered; so that, when the streams are accelerated by uplift, erosion is at first much more rapid in the soft surface rock than it is when the fresh rock be- neath is reached : hence, if the i;plift in any region is but one or two hundred feet, the streams may encounter only soft material in forming the new peneplain ; whereas, if the uplift is one or two thousand feet, far the greater part of their work will be in hard, unweathered material. Now, it was shown that in the Southern Appalachians two peneplains are sulheieutly well pre- served so that we are able to reconstruct their surfaces, and determine the amount of uplift which they have subsequently undergone. In both of these cases the uplift terminating one base-leveling cycle and inaugurating another has been unequal, greatest near the cidmiuating point of the Appalachians, and gradually decreasing southwestward. Moreovei", it seems proba- ble that the elevation of previous i)eneplains in the same region has been of the same character, greatest toward the north, and decreasing soiithwestward : hence the present decrease in altitude of the Southern Appalachian Mountains toward the southwest, and the corresponding increase in the proportion of area occupied by base-leveled valleys, are traced directly to differential uplift in recent geologic periods.

INFLUENCE OF PHYSIOGRAPHY ON SOCXAX, AND INDUSTRIAL DEVELOPMENT.

The physiography of any region determines to a large extent the character of the social and industrial development of its

INl'U'ENCE ON .SOCI.VL UEVELurMENT. oo3

people. It als(j lias an iiiflueiico .soinewhat Ifss diret't oti their moral and intellectual develupnieut. Some of the more obvious ways in which the physiography of the Southern Appalachians has aifected the ijeoplc and institutions will be pointed out.

The first settlenjent of the region was along th(> Atlantic (joast and up the navigable rivers to the "fall line." Here the streams leave their rocky channels on the Piedmont, by a series of rapids and falls, for deep cliannels across the Coastal Plain. At the head of navigation on the rivei's, trading posts wei'e at first established, which have since developed into thriving cities. From these outposts pioneers pushed farther inlaml ov'er the whole Piedmont Plain, and up to the heads of tlie fei'tile valleys among the eastern spurs of the Appalachian Mountains. For a time the Blue Ridge checked furtlier advance westward ; but this was soon crossed, and the interniontane valleys upon its western side occupied. Beyond these were the ragged Unakas, which long presented an insurmountable obstacle to further progre.ss. To th(^ natural difficulties of ti'avel were added the dangers from the warlike (Jhei'okee Indians, who found the thirk, narrow ravines well suited for their mode of waii'are.

Hunters brought back to the eastei-n settlements alluring tales of rich valley lands beyond the mountains, and even before the Revolution a few hardy pioneers had settled iu the Appala- chian Valley. Unable to pass the Unaka Range, two possible routes to the region W(n"e left, — one by way of the James or Roanoke gaps, through the Bhu' Ridge, and thence southwest- ward down the valley ; and the other through northern Georgia, around tlie soutlnM-n end of tTie mountain ranges. The latter I'oiite was little used on account of the hostile Creeks and (,'hero- kees, and nearly the entire immigration of the western portion of the Appalachians came in by the northern route. In the early decades of the century the region was I'apidly settled, chiefly from the Carolinas, Virginia, and (xeorgia. The Cherokees were gi'adually crowded within narrower limits as their rich lands were first coveted and then ajiprojiriated by the whites. Finally, between 1830 and lS4(t, theii- liunting grounds were i)urchased by the Fedei'al Government, and most of the tribe was re- moved to the Indian Territory. A few families of the tiibe refused to leave their old home, and coidd not be dislodged from the remote mountain valleys to which they had retreated. Their descendants still occupy a small reservation in west-

334 THE SOUTHERN APPALACHIANS.

evil North Carolina, only jiartially oivilizcd l>y coutact with their neighbors.

The Appalachian Mountains, and in some measure also the Cumberland Plateaus, thus acted as barriers to the advance of settlement ; so that the tide of immigration was for a time cheeked, and turned from the more direct course to one which oifered less resistance. With the advent of railroads the same lines of least resistance were followed which had directed tlie tide of immigration. The products of the interior sought an outlet to the east ; but from the Koanoke southward for 350 miles the Appalachian Mountains offered a serious obstacle, and not until after 1880 was this portion of the mountain belt crossed by any raih'oad. Past the southern end of the mountains, through north- ern Georgia, there was a natural outlet for the interior across the base-leveled plain already described ; and this was utilized for one of the earliest roads built in the South.

Few obstacles were met in building roads on the Piedmont Plain, and comparatively few in the Ap})alachian Valley. AVhere these natural routes are intersected by the transverse route across the mountain belt, there thriving cities have grown up. Atlanta, the " date City," stands at the portal of the Southern Appalachians, on the only natural route from the Tennessee basin to the southeast.

For a long distance on either side of Chattanooga, both to- ward the north and south, the Cumberland Plateaus present high, steep escarpinents toward the valley, offering serious, if not in- superable, obstacles to east and west roads. Toward the west, however, the plateaus are deepfy cut by transverse streams, along which roads have been built with <-omparative ease. Thus Chattanooga is also a " gate city," standing at the portal through which must pass all traffic between the great Interior Lowlands and the Southern Appalachian Valley.

Ease of communication is so important a factor in modern social development, that regions abundantly supplied "with I'ail- roads advance far beyond those still dependent t)u less I'apid transit : hence there are greater differences between the social conditions in the valleys and among the mountains than could possibly exist when th(> two regions were more nearly on an equality in this respect. The peojde remote from railroads are relatively much more isolated than they were when the only means of travel between the different parts of the country were

INFLUENCE ON SUCl.YL DEVELOPMENT. 335

on horseback or by stage. Many of the people in this region have been scarcely at all affected by the modern industrial and social revolutions which have been going on around them. In some of tlie more remote mountain valleys the mode of life doi's not diffei' essentially from that which jtrevailed throughout most of the country during colonial times. Practically everything consumed in the household is of'domcstic manufacture, and tlit- people have few wants which must be supplied from the out- side world. In these isolated communities are found the direct descendants of early Virginia and Carolina immigrants, Avitii scarcely a trace of foreign admixture. They are perhaps tin- purest stock in the United Statesi. Curious archaic customs and forms of speech are preserved among them which have entirely disappeared elsewhere.

There is still another way in which physiography has affected the people, scarcely less important than by controlling the ease of intercommunication between communities. Until within a few years the people of the Southern Appalachian region have been engaged almost exclusively in agricultural pursuits. Differences in soil and climate have determined the crops which could be raised with profit, and hence mode of cultivation and social con- ditions. Only the lowlands on either side of the Appalachians and the southern portion of the Great Valley were suited to the cultivation of cotton: hence in the highlands, where diversified crops and small farms were the rule, the institution of slavery did not gain a firm footing, as it did in the cotton-raising districts. Some counties of North Carolina even now do not contain a single negro. These tlitt'erent social conditions which prevailed for two generations prior to the Civil War, and which were traceable dii'ectly to i)hysiographic causes, have left effects upon the people which will i-e(|nii'e many years to eradicate.

The industi'ial revolution now in progress in the South, by which it is being converted from a i)ur<^ly agricultural to a manu- facturing region, is due in large part to physiographic causes. Within a belt embracing the eastern portion of the plateau and the western edge of the valley, conditions are extremely favor- able for the cheap production of iron. Fuel from the plateaus, and ore and flux from the valley, are brought together Avitli a minimum of expense; and manufacturing towns are springing up within this l)elt from Virginia to central Alabama.

:i'iHi THE SOUTHERN APPAL-iCHIANS.

Cheap j)ower is even more important tliau abundant raw mate- lials in bixikliiig up manufactures ; and, with modern improved methods for the trausmissit)n of power by electricity, water is to some extent rephicing steam. The Southern A])pakichians are rich in water power. The streams whicli flow westward from the mountain belt hjiv(» large catchment basins in the high inter- montane valleys. In tlieir courses to the A]ipalachian Valley are many rapids, particularly where they l)reak through the Unaka Range; and much of the power now going to waste in these rapids will undoubtedly be utilized before many decades. The manufacturing communities resulting from this utiUzation will be directly due to recent uplift of the Appalachian Moun- tain belt.

It is thus seen that the i)hysiography of the Southern Appa- lachians determined lines of early settlement, and directed the subsequent tide of immigration l)y which the region was peo- {>led; that it determined the lines of traffic and travel, the location of cities, and the relative development of different communities; that it determined the occupations and there- 1 )y the social conditions in different portions of the region ; and, finally, that it must in future exercise an important influence upon its industrial development and the material welfare of its people.

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