[Sidenote: Mountains as transit regions.]

Mountain regions, like deserts and seas, become mere transit districts, which man traverses as quickly as possible. Hence they often lie as great inert areas in the midst of active historical lands, and first appear upon the historical stage in minor roles, when they are wanted by the plains people as a passway to desirable regions beyond. Then, as a rule, only their transit routes are secured, while the less accessible regions are ignored. Caesar makes no mention of the Alps, except to state that he has crossed them, until some of the mountain tribes try to block the passage of Roman merchants or armies; then they become important enough to be conquered. It was not till after the Cimbri in 102 B.C. invaded Italy by the Brenner route, that the Romans realized the value of Rhaetia (Tyrol) as a thoroughfare from Italy to Germany, and began its conquest in 36 B.C. This was the same value which the Tyrol so long had for the old German Empire and later for Austria,—merely to secure connection with the Po Valley. The need of land communication with the Rhone Valley led the Romans to attack the Salyes, who inhabited the Maritime Alps, and after eighty years of war to force from them the concession of a narrow transit strip, twelve stadia or one and a half miles wide, for the purpose of making a road to Massilia.[1188] The necessity of controlling such transit lands has drawn British India into the occupation of mountain Baluchistan, Kashmir and Sikkim, just as it has caused the highlands of Afghanistan to figure actively in the expansion policy of both India and Russia. The conquest of such transit lands has always been attended by road building, from the construction of the Roman highway through the Brenner Pass to the modern Russian military road through the Pass of Dariel across the Caucasus, and the yet more recent Indian railroad to Darjeeling, with the highway extension beyond to the Tibetan frontier through Himalayan Sikkim.

Such mountain regions attain independent historical importance when their population increases enough to form the nucleus of a state, and to acquire additional territory about the highland base either by conquest or voluntary union, while they utilize their naturally protected location and their power to grant safe transit to their allies, as means to secure their political autonomy. Therefore to mountain regions so often falls the role of buffer states. Such were medieval Burgundy and modern Savoy, which occupied part of the same territory, Navarre which in the late Middle Ages controlled the important passway around the western end of the Pyrenees, and Switzerland which commands the passes of the central Alps. The position of such mountain states is, however, always fraught with danger, owing to the weakness inherent in their small area and yet smaller allowance of productive soil, to their diverse ethnic elements, and the forces working against political consolidation in their deeply dissected surface. Political solidarity has a hard, slow birth in the mountains.

[Sidenote: Transition forms of relief between highlands and lowlands.]

In view of the barrier character of mountains, a fact of immense importance to the distribution of man and his activities is the rarity of abrupt, ungraded forms of relief on the earth's surface. The physiographic cause lies in the elasticity of the earth's crust and the leveling effect of weathering and denudation. Everywhere mountains are worn down and rounded off, while valleys broaden and fill up to shallow trough outlines. Transition forms of relief abound. Human intercourse meets therefore few absolute barriers on the land; but these few reveal the obstacles to historical movement in perpendicular reliefs. The mile-high walls of the Grand Canon of the Colorado are an insuperable obstacle to intercourse for a stretch of three hundred miles. The glacier-crowned ridge of the Bernese Alps is crossed by no wagon road between the Grimsel Pass and the upper Rhone highway around their western end, a distance of 100 kilometers (62 miles). The Pennine Alps have no pass between the Great St. Bernard and the Simplon, a distance of 90 kilometers (54 miles).

[Sidenote: Importance of transition slopes.]

Gentle transition slopes or terrace lands facilitate almost everywhere access to the lowest, most habitable and therefore, from the human standpoint, most important section of mountains. They combine the ease of intercourse characteristic of plains with many advantages of the mountains, and especially in warm climates they unite in a narrow zone both tropical and temperate vegetation. The human value of these transition slopes holds equally of single hills, massive mountain systems, and continental reliefs. The earth as a whole owes much of its habitability to these gently graded slopes. Continents and countries in which they are meagerly developed suffer from difficulty of intercourse, retarded development and poverty of the choicest habitable areas. This is one disadvantage of South Africa, emphasized farther by a poor coastline. The Pacific face of Australia would gain vastly in historical importance, if the drop from the highlands to the ocean were stretched out into a broad slope, like that which links our Atlantic coastal plain with the Appalachian highlands. There each river valley shows three characteristic anthropo-geographical sub-divisions—the active seaports and tide-water tillage of its lower course, the contrasted agriculture of its hilly course, the upland farms, waterpower industries and mines of its headstream valleys, each landscape giving its population distinctive characteristics. The same natural features, with the same effect upon human activities and population, appear in the long seaward slopes of France, Germany and northern Italy.

[Sidenote: Piedmont belts as boundary zones.]

At the base of the mountains themselves, where the bold relief begins, is always a piedmont zone of hilly surface but gentler grade, at whose inner or upland edge every phase of the historical movement receives a marked check. Here is a typical geographical boundary, physical and human. It shifts slightly in different periods, according to the growing density of population in the plains below and improved technique in industry and road-making. It is often both an ethnic and cultural boundary, because at the rim of the mountains the geologic and economic character of the country changes.[1189] The expanding peoples of the plains spread over the piedmont so far as it offers familiar and comparatively favorable geographic conditions, scatter their settlements along the base of the mountains, and here fix their political frontier for a time, though later they may advance it to the crest of the ridge, in order to secure a more scientific boundary. The civilized population of the broad Indus Valley spread westward up the western highlands, only so far as the shelving slopes of the clay and conglomerate foothills, which constitute the piedmont of the Suleiman and Kirthar Mountains, afforded conditions for their crops. Thus from the Arabian Sea for 600 miles north to the Gomal River, the political frontier of India was defined by the line of relief dividing the limestone mountains from the alluvial plain, the marauding Baluch and Afghan hill tribes from the patient farmers of the Sind.[1190] This line remained the border of India from pre-British days till the recent annexation of Baluchistan.

These piedmont boundaries are most clearly defined in point of race and civilization, where superior peoples from the lowlands are found expanding at the cost of retarded mountain folk. Romans and Rhaetians once met along a line skirting the foot of the eastern Alps, as Russians to-day along the base of the Caucasus adjoin the territories of the heterogeneous tribes occupying that mountain area.[1191] [See map page 225.] The plains-loving Magyars of Hungary have pushed up to the rim of mountainous Siebenburgen or Transylvania from Arad on the Maros River to Sziget on the upper Theiss, while the highland region has a predominant Roumanian population. A clearly defined linguistic and cultural boundary of Indo-Aryan speech and religion, both Hindu and Mohammedan, follows the piedmont edges of the Brahmaputra Valley, and separates the lowland inhabitants from the pagans of Tibeto-Burman speech occupying the Himalayan slope to the north and the Khasia Mountains to the south. The highland race is Mongoloid, while the Bengali of an Aryan, Dravidian and Mongoloid blend fill the river plain.[1192] Such piedmont boundary lines tend to blur into bands or zones of ethnic intermixture and cultural assimilation. The western Himalayan foothills show the blend of Mongoloid and Aryan stocks, where the vigorous Rajputs of the plains have encroached upon the mountaineer's land.[1193] Of almost every mountain folk it can be assumed that they once occupied their highlands to the outermost rim of the piedmont, and retired to the inner rim of this intermediary slope only under compulsion from without.

[Sidenote: Density of population in piedmont belts.]

The piedmont boundary also divides two areas of contrasted density of population. Mountain regions are, as a rule, more sparsely settled than plains. The piedmont is normally a transition region in this respect; but where high mountains rise as climatic islands of adequate water supply out of desert and steppes, they concentrate on their lower slopes all the sedentary population, making their piedmonts zones of greatest density. Low mountains in arid regions become centers of population; here their barrier nature vanishes. In the Sudanese state of Darfur, the Marra Mountains are the district best watered and most thickly populated. Nowhere higher than 6000 feet (1850 meters), they afford running water at 4000 feet elevation and water pools in the sandy beds of their wadis at 3200 feet. Below this, water disappears from the surface, and can be found only in wells whose depth and scarcity increase with distance from the central mountains.[1194] The neighboring kingdom of Wadai shows similar conditions and effects.[1195] In the heart of Australia, where utter desert reigns, the Macdonnell Ranges form the nucleus of the northern area occupied by the Arunta tribe of natives; farther north the Murchison Range, usually abounding in water-holes, is the center and stronghold of the Warramunga tribe.[1196]

Mineral wealth or waterpower in the mountains serves to collect an urban and industrial population along their rim, as we see it about the base of the Erz Mountains in Saxony, the Riesen range in Silesia, the coal-bearing Pennine Mountains of northwestern England, and the highlands of southern Wales, all which piedmont zones show a density of over 150 to the square kilometer (385 to the square mile). Hence the original Swiss Confederation, which included only the mountain cantons of Schwyz, Uri and Unterwalden, was greatly strengthened by the accession of the piedmont cantons of Lucerne, Zurich, Zug and Bern in the early fourteenth century, as later by St. Gall, Aargau and Geneva. These marginal cantons to-day show a density of population exceeding 385 to the square mile, and rising to 1356 in the canton of Geneva.

[Sidenote: Piedmont towns and roads.]

Piedmont belts tend strongly towards urban development, even where rural settlement is sparse. Sparsity of population and paucity of towns within the mountains cause main of traffic to keep outside the highlands, but close enough to their base to tap their trade at every valley outlet. On the alluvial fans or plains of these valley outlets, where mountain and piedmont road intersect, towns grow up. Some of them develop into cities, when they command transverse routes of communication quite across the highlands. The ancient Via Aemilia traced the northern base of the Apennines from Ariminum on the Adriatic to Dertona at the foot of the Ligurian range back of Genoa, and connected a long line of Roman colonies. The modern railroad follows almost exactly the course of the old Roman road,[1197] while a transverse line southward across the Apennines, following an ancient highway over the Poretta Pass to the Arno Valley, has maintained the old preeminence of Bologna. A line of towns, connected by highways or railroads, according to the economic development of the section, defines the bases of the Pyrenees, Alps, Jura, Apennines, Harz, Vosges, Elburz and numerous other ranges. Along the Elburz piedmont runs the imperial road of Persia from Tabriz through Teheran to Meshed. In arid regions these piedmont roads are an unfailing feature, but their towns shrink to rural settlements, except at the junction of transmontane routes.

[Sidenote: Piedmont termini of transmontane routes.]

Piedmont cities draw their support from plain, mountain and transmontane region, relying chiefly on the fertile soil of the level country to feed their large populations. Sometimes they hug the foot of the mountains, as Bologna, Verona, Bergamo, Zurich, Denver and Pittsburg do; sometimes, like Milan, Turin, and Munich, they drop down into the plain, but keep the mountains in sight. They flourish in proportion to their local resources, in which mineral wealth is particularly important, and to the number and practicability of their transmontane connections. Hence they often receive their stamp from the mountains behind them as well as from the bordering plain. The St. Gotthard route is flanked by Lucerne on the north and Milan on the south. The Brenner has its urban outlets at Munich and Verona. Narbonne and Barcelona form the termini of the route over the eastern Pyrenees; Toulouse commands the less used central passes, and Bayonne the western. Tiflis is situated in the great mountain trough connecting the Black Sea and the Caspian; but over the Caucasus by the Pass of Dariel come the influences which make it a Russian town. Peshawar, situated in the mountain angle of the Punjab, depends more upon the Khaibar Pass and its connections thereby with Central Asia than upon the plains of the Indus; its population, in appearance and composition nearly as much Central Asiatic as Indian, is engaged in traffic between the Punjab and the whole trans-Hindu Kush country.[1198]

Where a mountain system describes a semi-circular course, its transit routes tend to converge on the inner side, and at their foci fix the sites of busy commercial centers. Turin draws on a long series of Alpine and Apennine routes from the Pass of Giovi (1548 feet or 472 meters) leading up from Genoa on the south, to the Great St. Bernard on the north. Milan gets immense support from the St. Gotthard and Simplon railroads over the Alps, besides wagon routes over several minor passes. Kulm, Balkh and Kunduz in the piedmont of northern Afghanistan are fed by twenty or more passes over the Hindu Kush and Pamir. Bukhara is the remoter focus of all these routes, and also of the valley highways of the western Tian Shan. It therefore occupies a location which would make it one of the great emporiums of the world, were it not for the expanse of desert to the west and the scantiness of its local water supply, which is tapped farther upstream for the irrigation of Samarkand. In its bazaars are found drugs, dyes and teas from India; wool, skins and dried fruit from Afghanistan; woven goods, arms, and books from Persia; and Russian wares imported by rail and caravan. English goods, which formerly came in by the Kabul route from India, have been excluded since Russia established a protectorate over the province of Bukhara. Across the highlands to the east, the cities of Kashgar and Yarkand, situated in that piedmont zone of vegetation where mountain and desert meet, are enclosed by a vast amphitheater formed by the Tian Shan, the Pamir Highlands, and the Karakorum range. Stieler's atlas marks no less than six trade routes over the passes of these mountains from Kashgar to the headstreams of the Sir-daria and Oxus, and six from Yarkand to the Oxus and Indus. Kashgar is a meeting ground of many nationalities. To its bazaars come traders from China, India, Afghanistan, Bukhara, and Russian Turkestan.[1199] The Russian railway up the Sir-daria to Andizhan brings European goods within relatively easy reach of the Terek Davan Pass, and makes serious competition for English wares entering by the more difficult Karakorum Pass from India.[1200]

[Sidenote: Cities of coastal piedmonts.]

Where mountains drop off into a desert, as these Central Asiatic ranges do, their piedmont cities are confined to a narrow zone between mountains and arid waste. Bordering two transit regions of scant population and through travel, they become natural outfitting points, centers of exchange rather than production. Where mountains drop off into the sea and the piedmont therefore becomes a coastal belt, again it borders two transit regions; but here the ports of the desert are replaced by maritime ports, which command the world thoroughfare of the ocean. They therefore tend to concentrate population and commerce wherever a good harbor coincides with the outlet of a transmontane route, as in Genoa and Bombay.

[Sidenote: Piedmonts as colonial or backwoods frontiers.]

Since mountains are inhospitable to every phase of the historical movement, they long remain regions of retardation. Hence to their bordering plains they sustain the relation of young undeveloped lands, so that life in their piedmont belts tends to show for a long time all the characteristics of a new colonial frontier. The rim of the Southern Appalachians abundantly illustrates this principle even to-day. During the westward expansion of the American people from 1830 to 1850, the eastern rim of the Rocky Mountains was dotted with trading posts like that of the Missouri Fur Company at the forks of the Missouri River, Forts Laramie and Platte on the North Fork of the Platte, Vrain's Fort and Fort Lancaster on the South Fork, Bent's Fort at the mountain exit of the Arkansas River, and Barclay's in the high Mora Valley of the upper Canadian. These posts gathered in the rich pelts which formed the one product of this highland area susceptible of bearing the cost of transportation to the far away Missouri River. Though they developed into way-stations on the overland trails, when the movement of population to California and Oregon in the forties and fifties made the Rocky Mountains a typical highland transit region, yet they long remained frontier posts.[1201] Later the abundant water supply of this piedmont district, as compared with the arid plains below, and the mineral wealth of the mountains concentrated here an agricultural and industrial population.

In Sze Chuan province of western China, the piedmont of a vast highland hinterland shows a similar development. Here the towns of Matang, Sungpan, Kuan Hsien, and even the capital Chengtu, situated in the high Min Valley at the foot of the mountains walling them in on the west, are emporiums for trade with the Tibetans, who bring hither furs, hides and wool from their plateau pastures, and musk from the musk deer on the Koko Nor plains.[1202] Just to the north, Sian (Singan), capital of the highland province of Shensi, concentrates the fur trade of a large mountain wilderness to the west. Several blocks on the main street form a great fur market for the sale of mink and other skins used to line the official robes of mandarins.[1203]

[Sidenote: Mountain carriers.]

Like seas, deserts, and other geographical transit regions, mountains too under primitive conditions develop their professional carriers. These collect in the piedmont, where highway and mule train cease, and where the steep track admits only human beasts of burden, trained by their environment to be climbers and packers. These mountain carriers are found on the Pacific face of the coast ranges of North and South America from the peninsula of Alaska to the Straits of Magellan. They are able to pack from 100 to 160 pounds up a steep grade. The Chilkoot Indians, men, women and children, did invaluable service on the White Horse and Chilkoot passes during the early days of the Klondike rush. They had devised a well-arranged harness, which enabled them better to carry their loads. Farther south in British Columbia the piedmont tribes had once a like importance; there they operated especially from the town of Hope on the lower Frazer River as a distributing center. The Mexican carrier is so efficient and so cheap that he enters into serious competition with modern schemes to improve transportation, especially as the rugged relief of this country makes those schemes expensive.[1204] The Indians of the eastern slope of the Andes pack India rubber, in loads of 150 pounds each, from the upper Purus and Madeira rivers up to the Andean plateau at a height of 15,000 feet, and there transfer their burdens to mules for transport down to the Peruvian port of Mollendo.[1205]

The retarded mountain peoples on the borders of the Central Asia plateau employ the same primitive means of transportation. The roads leading from the Sze Chuan province of western China over the mountain ranges to Tibet are traversed by long lines of porters, men, women and children, laden with bales of brick tea,[1206] the strongest of them shouldering 350 pounds. The Bhutia coolies of Sikkim act as carriers on military and commercial expeditions on the track across the Himalayas between Darjeeling and Shigatze. Colonel Younghusband found that these Bhutias, who were paid by the job, would carry a pack of 250 to 300 pounds, or three times the usual burden of a Central Asia carrier. Landon cites the case of a Bhutia lady who was said to have carried a piano on her head from the plains up to Darjeeling (7150 feet).[1207] In Nepal, women and girls, less often men, have long been accustomed to carry travellers and merchandise over the Himalayan ranges.[1208] In the marginal valleys of the Himalayas, like Kashmir and Baltistan, the natives are regularly impressed for begar or carrier service on the English military roads to strategic points on the high mountain frontier of the Indian Empire.[1209] So the Igorots of the Luzon province of Benguet pack all goods and supplies from Naguilian in the lowlands up 4000 feet in a distance of 25 miles to their little capital of Baguio; for this service they are now paid one peso (46 cents in 1901) a day with food, or ten times as much as under the Spanish rule.[1210]

[Sidenote: Power of mountain barriers to block or deflect.]

If the historical movement slackens its pace at the piedmont slope, higher up the mountain it comes to a halt. Only when human invention has greatly improved communication across the barrier are its obstacles in part overcome. The great highland wall stretching across southern Europe from the Bay of Biscay to the Black Sea long cut off the solid mass of the continent from the culture of the Mediterranean lands. Owing to these mountains Central Europe came late into the foreground of history, not till the Middle Ages. Even the penetrating civilization of Greece reached it only by long detours around the ends of the mountain barrier; by Massilia and the Rhone, by Istria and the Danube, Greek commerce trickled through to the interior of the continent.

Where mountains fail to check, they deflect the historical movement. The wall of the Carpathians, bulwark of Central Europe, split the westward moving Slav hordes in the 6th century, diverting one southward up the Danube Valley to the Eastern Alps, and turning one northward along the German lowlands.[1211] The northward expansion of the Romans, rebuffed by the high double wall of the Central Alps, was bent to the westward over the Maritime, Cottine and Savoy Alps, where the barrier offered the shortest and easiest transmontane routes. Hence Germany received the elements of Mediterranean culture indirectly through Gaul, second-hand and late. The ancient Helvetians, moving southward from northern Switzerland into Gaul, took a route skirting the western base of the Alps by the gap at Geneva, and thus threatened Roman Provincia. Caesar's campaigns into northern Gaul were given direction by the massive Central Plateau of France.[1212] The rugged and infertile area of the Catskills long retarded the westward movement in colonial New York and deflected it northward through the Mohawk depression, which therefore had its long thin line of settlements when the neighboring Catskills were still a "bare spot."

[Sidenote: Significance of mountain valleys.]

In their valleys, mountains lose something of their barrier nature, and approximate the level of the plains. Here they harbor oases of denser population and easier intercourse. Valleys favor human settlement through the milder climate of their lower elevation, the accumulation of soil on their floors, their sheltered environment, and their command of such routes of communication as the highlands afford. They are the avenues into and within a mountain system, and therefore radically influence its history by their direction and location. The Central Plateau of France, through the valleys of the Alliers and upper Loire, is most accessible from the north; therefore in that direction it has maintained its most important historical connections,[1213] from the days of Caesar and Vercingetorix. The massive highland region of Transylvania, which opens long accessible valleys westward toward the plains of the Theiss and Danube, has since the eleventh century received thence Hungarian immigration and political dominion.[1214] Its dominant Roumanian population, however, seems to have fled thither from the Tartar-swept plains to the southeast.

The anthropo-geography of mountain valleys depends upon the structure of the highlands themselves, whether they are fold mountains, whose ranges wall in longitudinal valleys, or dissected plateaus, whose valleys are mostly transverse river channels leading from the hydrographic center out to the rim of the highlands. Longitudinal valleys are not only long, but also broad as a rule and often show a nearly level floor.[1215] They therefore form districts of considerable size, fertility, and individuality, and play distinct historical roles in the history of their respective highlands. Such are the upper Rhone Valley with its long line of flourishing towns and villages, the Hither Rhine, the Inn of the Tyrol and the Engadine, the fertile trough of the meandering Isere above Grenoble,[1216] the broad Orontes-Leontes valley between the Lebanon and Anti-Lebanon where Kadesh and Baalbec were once the glory of northern Syria. Such is the central trough of the Appalachian Mountains, known as the Great Appalachian Valley, seventy-five miles wide, subdivided into constituent valleys of similar character by parallel, even-crested ridges following the trend of the mountains. These are drained by broad, leisurely rivers, bordered by fertile farms and substantial towns. Transverse valleys, on the other hand, are generally narrow, with steep slopes rising almost from the river's edge and supporting only small villages and farms. A comparison of the spacious, smooth-floored valley of Andermatt with the wild Reuss gorge, of the fertile and populous Shenandoah Valley in the Southern Appalachians with the canon of the Kanawha in the Cumberland Plateau, makes the contrast striking enough.

[Sidenote: Longitudinal valleys.]

Longitudinal valleys, by reason of their length and their branching lateral valleys, are the natural avenues of communication within the mountains themselves. They therefore give a dominant direction to such phases of the historical movement as succeed in passing the outer barrier. The series of parallel ranges which strike off from the eastern end of the Tibetan plateau southward into Farther India have directed along their valleys the main streams of Mongolian migration and expansion, heading them toward the river basins of Burma and Indo China, and away from India itself.[1217] While Tibetan elements have during the ages slowly welled over the high Himalayan brim and trickled down toward the Gangetic plain, Burma has been deluged by floods of Mongolians pouring down the runnels of the land. A carriage road follows the axis of the Central Alps from Lake Geneva to Lake Constance by means of the upper Rhone, Andermatt, and upper Rhine valleys, linked by the Furca and Oberalp passes. The Roman and Medieval routes northward across the Central Alps struck the upper Rhine Valley above Coire, (the ancient Curia Rhaetorum); this natural groove gave them a northeastward direction, and made them emerge from the mountains directly south of Ulm, which thereby gained great importance. The trade routes from Damascus and Palmyra which once entered the Orontes-Leontes trough in the Lebanon system found their Mediterranean termini south near Tyre or north near Antioch, and thus contributed to the greatness of those ancient emporiums. The Great Appalachian Valley used to be a highway for the Iroquois Indians, when they took the warpath against the Cherokee tribes of Tennessee. Later it gave a distinct southwestward trend to pioneer movements of population within the mountains, blending in its common channel the Quakers, Germans and Scotch-Irish from Pennsylvania, with the English and Huguenot French of the more southern colonies. In the Civil War its fertile fields were swept by marching armies, all the way from Chattanooga to Gettysburg.

[Sidenote: Passes in mountain barriers.]

The barrier nature of mountains depends upon their height and structure, whether they are massive, unbroken walls like the Scandinavian Alps and the Great Smoky range; or, like the Welsh Highlands and the Blue Ridge, are studded with low passes. The Pyrenees, Caucasus and Andes, owing to the scarcity and great height of their passes, have always been serious barriers. The Pyrenees divide Spain from France more sharply than the Alps divide Italy from France; owing to their rampart character, they form the best and most definite natural boundary in Europe.[1218] Epirus and Aetolia, fenced in by the solid Pindus range, took little part in the common life of ancient Greece; but the intermittent chains of Thessaly offered a passway between Macedon and Hellas. The Alps have an astonishing number of excellent passes, evenly distributed for the most part. These, in conjunction with the great longitudinal valleys of the system, offer transit routes from side to side in any direction. The Appalachian system is some three hundred miles broad and thirteen hundred miles long, but it has many easy gaps among its parallel ranges, so that it offered natural though circuitous highways to the early winners of the West. The long line (400 miles) of the Hindu Kush range, high as it is, forms no strong natural boundary to India, because it is riddled with passes at altitudes from 12,500 to 19,000 feet.[1219] The easternmost group of these passes lead down to Kashmir, and therefore lend this state peculiar importance as guardian of these northern entrances to India.[1220] The Suleiman Mountains along the Indo-Afghan frontier are an imperfect defence for the same reason. They are indented by 289 passes capable of being traversed by camels. The mountain border of Baluchistan contains 75 more, the most important of which focus their roads upon Kandahar. Hence the importance to British India of Kandahar and Afghanistan. Across this broken northwest barrier have come almost all the floods of invasion and immigration that have contributed their varied elements to the mixed population of India. Tradition, epic and history tell of Asiatic highlanders ever sweeping down into the warm valley of the Indus through these passes; Scythians, Aryans, Greeks, Assyrians, Medes, Persians, Turks, Tartars, and Mongols have all traveled these rocky roads, to rest in the enervating valleys of the peninsula.[1221]

[Sidenote: Breadth of mountain barriers.]

Mountains folded into a succession of parallel ranges are greater obstructions than a single range like the Erz, Black Forest, and Vosges, or a narrow, compact system like the Western Alps, which can be crossed by a single pass. Owing to this simple structure the Western Alps were traversed by four established routes in the days of the Roman Empire. These were: I. The Via Aurelia between the Maritime Alps and the sea, where now runs the Cornice Road. II. The Mons Matrona (Mont Genevre Pass, 6080 feet or 1854 meters [Transcriber's Note: printer's error incorrectly printed as kilometers.]) between the headstream of the Dora Riparia and that of the Durance, which was the best highway for armies. III. The Little St. Bernard (7075 feet or 2157 meters), from Aosta on the Dora Baltea over to the Isere and down to Lugdunum (Lyons). IV. The Great St. Bernard (8109 feet or 2472 meters) route, which led northward from Aosta over the Pennine Alps to Octodurus at the elbow of the upper Rhone, where Martigny now stands. Across the broad double rampart of the Central Alps the Roman used chiefly the Brenner route, which by a low saddle unites the deep reentrant valleys of the Adige and Inn rivers, and thus surmounts the barrier by a single pass. However, a short cut northward over the Chalk Alps by the Fern Pass made closer connection with Augusta Vindelicorum (Augsburg). The Romans seem to have been ignorant of the St. Gotthard, which, though high, is the summit of an unbroken ascent from Lake Maggiore up the valley of the Ticino on one side, and from Lake Lucerne up the Reuss on the other.

Mountains which spread out on a broad base in a series of parallel chains, and through which no long transverse valleys offer ready transit, form serious barriers to every phase of intercourse. The lofty boundary wall of the Pyrenees, a folded mountain system of sharp ranges and difficult passes, has successfully separated Spain from continental Europe; it has given the Iberian Peninsula, in the course of a long history, closer relations with Morocco than with its land neighbor France. It thus justifies the French saying that "Africa begins at the Pyrenees." The Andalusian fold mountains stretching across southern Spain in a double wall from Trafalgar to Cape Nao, accessible only by narrow and easily defended passes, enabled the Moors of Granada to hold their own for centuries against the Spaniard Christians. The high thin ridges of the folded Jura system, poor in soil and sparsely populated, broken by occasional "cluses" or narrow water-gaps admitting the rivers from one elevated longitudinal valley to another, have always been a serious hindrance to traffic.[1222]

[Sidenote: Circuitous routes through folded mountains.]

Such mountains can be crossed only by circuitous routes from pass to pass, ascending and descending each range of the system. The Central Alps, grooved by the longitudinal valleys of the upper Rhone, Rhine and Inn, make transit travel a series of ups and downs. The northern range must be crossed by some minor pass like the Gemmi, (7553 feet) or Panixer (7907 feet) to the longitudinal valleys, and the southern range again by the Simplon (6595 feet), San Bernadino (6768 feet), Spluegen (6946 feet) or Septimer (7582 feet) to the Po basin. Across the corrugated highland of the Hindu Kush, lying between the plains of the Indus and the Oxus, the caravans of western Asia seek the market of the Punjab by a circuitous route through the Hajikhak Pass (12,188 feet) or famous Gates of Bamian over the main range of the Hindu Kush, by the Unai Pass over the Paghman Mountains to Kabul at 5740 feet, and then by gorges of the Kabul River and the Khaibar Pass (6825 feet) down to Peshawar. This road presents so many difficulties that caravans from Turkestan to India prefer another route from Merv up the valley of the Heri-Rud through the western hills of the Hindu Kush to Herat, thence diagonally southeast across Afghanistan to Kandahar, and thence by the Bolan Pass down to the Sind. The broad, low series of forested mountains consisting of the Vindhyan and Kaimur Hills, reinforced by the Satpura, Kalabet, Gawilgarh ranges, Mahadeo Hills, Maikal Range and Chutia Nagpur Plateau as a secondary ridge to the south, forms a double barrier across the base of peninsular India. It divides the Deccan from Hindustan so effectually that it has sufficed to set limits to any Aryan advance en masse southward. It kept southern India isolated, and admitted only later Aryan influences which filtered through the barrier. To people accustomed to treeless plains, these wide belts of wooded hills were barrier enough. Even a few years ago their passes were dreaded by cartmen; most of the carriage of the country was effected by pack-bullocks. Even when roads were cleared through the forests, they were likely to be rendered impassable by torrential rains.[1223]

[Sidenote: Dominant trans-montane routes.]

Where a broad, complex mountain system contracts to narrow compass, or is cut by deep reentrant valleys leading up to a single pass, the transmontane route here made by nature assumes great historical Importance. The double chain of the mighty Caucasus, from 120 to 150 miles wide and 750 miles long, stretches an almost insuperable barrier between the Black Sea and the Caspian. But nearly midway between these two seas it is constricted to only 60 miles by a geographical and geological gulf, which penetrates from the steppes of Russia almost to the heart of the system.[1224] This gulf forms the high valley of the Terek River, beyond whose headstream lies the Dariel defile (7503 feet or 2379 meters), which continues the natural depression across to the short southern slope. All the other passes of the Caucasus are 3000 meters or more high, lie above snow line and are therefore open only in summer. The Dariel Pass alone is open all the year around.[1225] Here runs the great military road from Vladicaucas to Tiflis, which the Russians have built to control their turbulent mountaineer subjects; and here are located the Ossetes, the only people among the variegated tribes of the whole Caucasus who occupy both slopes. All the other tribes and languages are confined to one side or the other.[1226] Moreover, the Ossetes, occupying an exposed location in their highway habitat, lack the courage of the other mountaineers, and yielded without resistance to the Russians. In this respect they resemble the craven-spirited Kashmiri, whose mountain-walled vale forms a passway from Central Asia down to the Punjab.

[Sidenote: Brenner route.]

The Pass of Dariel, owing to its situation in a retarded Brenner corner of Asia, has never attained the historical importance which attaches to the deep saddle of the Brenner Pass (4470 feet) in the Central Alps. Uniting the reentrant valleys of the Inn and Adige rivers only 2760 feet above the Inn's exit from the mountains upon the Bavarian plateau, it forms a low, continuous line of communication across the Central Alps. The Brenner was the route of the Cimbri invading the Po Valley, and later of the Roman forces destined for frontier posts of the Empire on the upper Danube. In the Middle Ages it was the route for the armies of the German Emperors who came to make good their claim to Italy. By this road came the artists and artisans of the whole north country to learn the arts and crafts of beauty-loving Venice. From the Roman road-makers to the modern railroad engineer, with the concomitant civilization of each, the Brenner has seen the march of human progress.

[Sidenote: Pass of Belfort.]

Farther to the west, the wall of highlands stretching across southern Europe is interrupted by a deep groove formed by the mountain-flanked Rhone Valley and the Pass of Belfort, or Burgundian Gate, which lies between the Vosges and Jura system, and connects the Rhone road with the long rift valley of the middle Rhine. This pass, broad and low (350 meters or 1148 feet) marks the insignificant summit in the great historic route of travel between the Mediterranean and the North Sea, from the days of ancient Etruscan merchants to the present. This was the route of the invading Teuton hordes which the Roman Marius defeated at Aquae Sextiae, and later, of the Germans under Ariovistus, whom Caesar defeated near the present Muehlhausen. Four centuries afterward came the Alamannians, Burgundians and other Teutonic stocks, who infused a tall blond element into the population of the Rhone Valley.[1227] The Pass of Belfort is the strategic key to Central Europe. Here Napoleon repeatedly fixed his military base for the invasion of Austria, and hither was directed one division of the German army in 1870 for the invasion of France. The gap is traversed to-day by a canal connecting the Doubs and the Rhine and by a railroad, just as formerly by the tracks of migrating barbarians.

[Sidenote: Mohawk route.]

The natural depression of the Mohawk Valley, only 445 feet (136 meters) above sea level, is the only decided break across the entire width of the long Appalachian system. This fact, together with its ready accessibility from the Hudson on the east and Lake Ontario on the west, lent it importance in the early history of the colonies, as well as in the later history of New York. It was an easy line of communication with the Great Lakes, and gave the colonists access to the fur trade of the Northwest, then in the hands of the French. So when French and English fought for supremacy in the New World, the Mohawk and Hudson valleys were their chief battleground; elsewhere the broad Appalachian barrier held them apart. Again in the Revolution, control of the Mohawk-Hudson route was the objective of the British armies mobilized on the Canadian frontier, because it alone would enable them to co-operate with the British fleet blockading the coast cities of the colonies. In the War of 1812, it was along this natural transmontane highway that supplies were forwarded to the remote frontier, to support Perry's fight for control of the Great Lakes. The war demonstrated the strategic necessity of a protected, wholly American line of water communication between the Hudson and our western frontier, while the commercial and political advantage was obvious. Hence a decade after the conclusion of the war, this depression was traced by the Erie Canal, through which passed long lines of boats to build up the commercial greatness of New York City.

[Sidenote: Height in mountain barriers.]

Other structural features being the same, mountains are barriers also in proportion to their height; for, with few exceptions, the various anthropo-geographic effects of upheaved areas are intensified with increase of elevation. Old, worn-down mountains, like the Appalachians and the Ural, broad as they are, have been less effective obstacles than the towering crests of the Alps and Caucasus. The form of the elevation also counts. Easy slopes and flat or rounded summits make readier transit regions than high, thin ridges with escarpment-like flanks. Mountains of plateau form, though reaching a great altitude, may be relatively hospitable to the historical movement and even have a regular nomadic population in summer. The central and western Tian Shan system is in reality a broad, high plateau, divided into a series of smoothly floored basins and gently rolling ridges lying at an elevation of 10,000 to 12,000 feet above the sea. Its pamirs or plains of thick grass, nourished by the relatively heavy precipitation of this high altitude, and forming in summer an island of verdure in the surrounding sea of sun-scorched waste, attract the pastoral nomads from all the bordering steppes and deserts.[1228] Thus it is a meeting place for a seasonal population, sparse and evanescent, but its uplifted mass holds asunder the few sedentary peoples fringing its piedmont. The corrugated dome of the Pamir highland, whose valley floors lie at an elevation of 11,000 to 13,000 feet, draws to its summer pastures Kirghis shepherds from north, east and west; and their flocks in turn attract the raids of the marauding mountaineers occupying the Hunza Valley to the south. The Pamir, high but accessible, was a passway in the tenth century for Chinese caravans bound from "Serica" or the "Land of Silk" to the Oxus River and the Caspian. Here Marco Polo and many travelers after him found fodder for their pack animals and food for themselves, because they could always purchase meat from the visiting shepherds. The possibilities of the Pamir as a transit region are apparent to Russia, who in 1886 annexed most of it to the government of Bukhara.

[Sidenote: Contrasted accessibility of opposite slopes.]

Mountains are seldom equally accessible from all sides. Rarely does the crest of a system divide it symmetrically. This means a steep, difficult approach to the summit from one direction, and a longer, more gradual, and hence easier ascent from the other. It means also in general a wide zone of habitation and food supply on the gentler slope, a better commissary and transport base whence to make the final ascent, whether in conquest, trade or ethnic growth. Mountain boundaries are therefore rarely by nature impartial. They do not umpire the great game of expansion fairly. They lower the bars to the advancing people on one side, and hold them relentlessly in place to the other. To the favored slope they give the strategic advantage of a swift and sudden descent beyond the summit down the opposite side. The political boundary of France along the watershed of the Vosges Mountains is backed by a long, gradual ascent from the Seine lowland and faces a sharp drop to the rift valley of the middle Rhine, Its boundary along the crest of the Alps from Mont Blanc to the Mediterranean brings over two-thirds of the upheaved area within the domain of France, and gives to that country great advantages of approach to the Alpine passes at the expense of Italy. With the exception of the ill-matched conflict between the civilized Romans and the barbarian Gauls, it is a matter of history that from the days of Hannibal to Napoleon III, the campaigns over the Alps from the north have succeeded, while those from the steep-rimmed Po Valley have miscarried. The Brenner route favored alike the Cimbri hordes in 102 B.C. and later the medieval German Emperors invading Italy from the upper Danube. The drop from the Brenner Pass to Munich is 2800 feet; to Rovereto, an equally distant point on the Italian side, the road descends 3770 feet.

[Sidenote: Its ethnic effects.]

The inequality of slope has ethnic as well as political effects, especially where a latitudinal direction also makes a sharp contrast of climate on the two sides of the mountain system. Except in the Roman period, the southern face of the Alps has been an enclosing wall to the Italians. The southern cultivator penetrated its high but sunny valleys only when forced by poverty, while the harsh climate on the long northern slope effectively repelled him. On the other hand, Switzerland has overstepped the Alpine crest in the province of Ticino and thrust its political boundary in a long wedge down to the lowland of the Po near Como; and the Alpine race, spilling everywhere over the mountain rim into the inviting Po basin, has given to this lowland population a relatively broad skull, blond coloring and tall figure, sharply contrasted with the pure Mediterranean race beyond the crest of the Apennines.[1229]

The long northward slope of the Alps in Switzerland and Tyrol, and the easy western grade toward France, have enabled Germanic and Gallic influences of various kinds to permeate the mountains. A strong element of blond, long-headed Germans mingles in the population of the Aar and Rhine valleys up to the ice-capped ridge of the Glarner and Bernese Alps,[1230] while the virile German speech has pushed yet farther south to the insuperable barrier of the Monte Rosa group. The abrupt southward slope of the Himalayas has repelled ethnic expansion from the river lowlands of northern India, except in the mountain valleys of the Punjab streams and Nepal, where the highland offered asylum to the Rajput race when dislodged by a later Aryan invasion, or when trying their energies in expansion and conquest.[1231] The Tibetan people, whose high plateaus rise almost flush with the Himalayan passes, have everywhere trickled through and given a Mongoloid mountain border to Aryan India,[1232] even though their speech has succumbed to the pervasive Aryan language of the piedmont, and thus confused the real ethnic boundary. [See map page 102.] The retarded and laborious approach of British "influence" up this steep ascent to Lhassa, as opposed to the long established suzerainty of the Chinese Emperor in Tibet, can be attributed in part to the contrasted accessibility from north and south.

[Sidenote: Persistence of barrier nature.]

Mountains influence the life of their inhabitants and their neighbors fundamentally and variously, but always reveal their barrier nature. For the occupants of one slope they provide an abundant rainfall, hold up the clouds, and rob them of their moisture; to the leeward side they admit dry winds, and only from the melting snow or the precipitation on their summits do they yield a scanty supply of water. The Himalayas are flanked by the teeming population of India and the scattered nomadic tribes of Tibet. Mountains often draw equally clear cut lines of cleavage in temperature. The Scandinavian range concentrates upon Norway the warm, soft air of the Atlantic westerlies, while just below the watershed on the eastern side Sweden feels all the rigor of a sub-Arctic climate. In history, too, mountains play the same part as barriers. They are always a challenge to the energies of man. Their beauty, the charm of the unknown beyond tempts the enterprising spirit; the hardships and dangers of their roads daunt or baffle the mediocre, but by the great ones whose strength is able to dwarf these obstacles is found beyond a prize of victory. Such were Hannibal, Napoleon, Suvaroff, Genghis Khan, and those lesser heroes of the modern work-a-day world who toiled across the Rockies and Sierras in the feverish days of '49, or who faced the snows of Chilkoot Pass for the frozen gold-fields of the Yukon.

[Sidenote: Importance of mountain passes.]

For migrating, warring and trading humanity therefore, the interest of the mountains is centered in the passes. These are only dents or depressions in the great up-lifted crest, or gaps carved out by streams, or deeper breaches in the mountain wall; but they point the easiest pathway to the ultramontane country, and for this reason focus upon themselves the travel that would cut across the grain of the earth's wrinkled crust. Their influence reaches far. The Brenner, by its medieval trade, made the commercial greatness of Augsburg, Ratisbon, Nuremberg, and Leipzig to the north, and promoted the growth of Venice to the south. The Khaibar Pass and the Gates of Herat in Afghanistan have for long periods dominated the Asiatic policy of Russia and British India. The Mohawk depression and Cumberland Gap for decades gave direction to the streams of population moving westward into the Mississippi basin in the early history of the Republic. Where Truckee Pass (7017 feet) makes a gash in the high ridge of the Sierra Nevada, the California Trail in 1844 sought the line of least resistance across the barrier mass, and deposited its desert-worn immigrants about the Sacramento Valley and San Francisco Bay. There they made a nucleus of American population in Mexican California, and in 1846 became the center of American revolt.

[Sidenote: Persistent influence of passes.]

Though modern engineering skill, especially when backed by a political policy, may cause certain passes to gain in historical importance at the cost of others, the rule holds that passes are never quite insignificant. Their influence is persistent through the ages. They are nature-made thoroughfares, traversed now by undisciplined hordes of migrating barbarians, now by organized armies, now by the woolly flocks and guardian dogs of the nomad shepherd, now by the sumpter mule of the itinerant merchant, now by the wagon-trains of over-mountain settlers, now by the steam engine panting up the steep grade. Nowhere does history repeat itself so monotonously, yet so interestingly as in these mountain gates. In the Pass of Roncesvalles, notching the western Pyrenees between Pamplona in Spain and St. Etienne in France, fell the army of Charlemagne surprised and beset by the mountain tribes in 778;[1233] through this breach the Black Prince in 1367 led his troops to the victory of Navarette; in the Peninsular War a division of Wellington's army in 1813 moved northward up this valley, driving the French before them; and by this route Soult advanced southward across the frontier for the relief of the French forces shut up in Pamplona. The history of Palestine may be read in epitome in the annals of the Vale of Jezreel, where the highlands of Palestine sink to a natural trough before rising again to the hill country of Galilee and the mountain range of high Lebanon. This was the avenue for war and trade between the Nile and Euphrates, between Africa and Asia. Here the Canaanites expanded eastward from the coast, cutting off northern Israel in Galilee from Samaria and Judea. Here Gideon turned back the incursions of the Midianites or western Arabs. Here was the open road for Assyrians, Egyptians, for Greek armies under Antiochus, and Roman armies under Pompey, Mark Antony, Vespasian and Titus. Hither came the Saracens from the east in 634 A. D. to rout the Greek army, and later the Crusaders from the west, to secure with castle and fortress this key to the Holy Land. Finally, hither came Napoleon from Egypt in 1799 on his way to the Euphrates.[1234]

[Sidenote: Geographic factors in the historical importance of passes.]

The historical importance of passes tends to increase with the depth of the depression, since the lowest gap in a range relegates the others to only occasional or local use; and with their rarity, in consequence of which intercourse between opposite slopes is concentrated upon one or two defiles. The low dips of the Central American Cordilleras to 262 feet (80 meters) at Panama, 151 feet (46 meters) in the Nicaraguan isthmus, and 689 feet (210 meters) at Tehuantepec, present a striking contrast both orographically and historically to the South American Andes, where from the equator to the Uspallata or Bermejo Pass (12,562 feet or 3842 meters) back of Valparaiso, a stretch measuring 33 degrees of latitude, the passes all reach or exceed 10,000 feet or 3000 meters. The southern or Pennine range of the Alps, stretching as a snow-wrapped barrier from Mont Blanc 90 miles to the central Alpine dome of the St. Gotthard, is notched only by the Great St. Bernard and Simplon passes, which have therefore figured conspicuously in war and trade, since very early times. The Pass of Thermopylae, as the only route southward along the flank of the Pindus system, figures in every land invasion of Greece from Xerxes to the Greek war of independence. All movements back and forth across the Caucasus wall have been confined to the Pass of Dariel and the far lower Pass of Derbent, or Pylae Albaniae; of the ancients, which lies between the Caspian and the last low spurs of the mountains as they drop down to the sea. The latter, as the easier of the two passes, has had a longer and richer history. It alone enabled the ancient Persians temporarily to force a wedge of conquest to the northern foot of the Caucasus, and it has been in all ages a highway for peoples entering Persia and Georgia from the north. It has so far been the only practicable route for a railway from the Russian steppes to the southern base of the Caucasus. While Vladicaucas and Tiflis have direct connection by the military highway over the Pass of Dariel, the railroad between these two points makes a detour of 300 miles to the east.

[Sidenote: Intermarine mountains.]

Intermarine mountains as a rule offer the easiest passways where they sink to meet the flanking seas. The Pyrenees are crossed by only two railroads, the Bayonne-Burgos line, along the shore of the Bay of Biscay, and the Narbonne-Barcelona line, overlooking the Mediterranean. Between these extremities the passes are very high and only two are practicable for carriages, the Col de la Perche (5280 feet or 1610 meters) between the valleys of the Tet and the upper Segre, and the Port de Canfranc (7502 feet or 2288 meters) on the old Roman road from Saragossa to Oloron. The coastal road around the eastern end of the Cheviot Hills has been the great intermediary between England and Scotland. It was the avenue for early Teutonic expansion into the Scotch Lowlands, the thoroughfare for all those armies which for centuries made Berwick a chronic battleground.

For purposes of trade these intermarine mountains are less serious barriers, because they can be avoided by an easier and cheaper sea route. Hence on each side of such ranges grow up active ports, like Narbonne and Barcelona, Bayonne and Bilbao with San Sebastian, on the piedmont seaboard of the Pyrenees; Petrovsk and Baku on the Caspian rim of the Caucasus, balancing the Crimean ports and Poti with Trebizond on the Black Sea. Analogous is the position of Genoa and Marseilles in relation to the Maritime Alps. Such ports are inevitably the object of attack in time of hostilities. In the Peninsular War almost the first act of the French was to seize Barcelona, San Sebastian and Bilbao; and throughout the seven years of the conflict these points were centers of battle, blockade and siege. If Russia ever tries to wrench the upper Euphrates Valley from Turkey, Trebizond will repeat the history of Barcelona in the Peninsular War.

[Sidenote: Pass roads between regions of contrasted production]

As the world's roads are used primarily for commerce, pass routes rank in importance according to the amount of trade which they forward; and this in turn is decided by the contrast in the lands which they unite. The passes of the Alps and the Pass of Belfort have been busy thoroughfares from the early Middle Ages, because they facilitate exchanges between the tropical Mediterranean and the temperate regions of Central Europe. Or the contrast may be one of economic and social development. The Mohawk depression forwards the grain of the agricultural Northwest in return for the manufactured wares of the Atlantic seaboard. The passes of the Asiatic ranges connect the industrial and agricultural lowlands of India and China with the highland pastures of Mongolia, Tibet, Afghanistan and Russian Turkestan. Hence they forward the wool, skins, felts, cloth and carpets of the wandering shepherds in exchange for the food stuffs and industrial products of the fertile, crowded lowlands. Where passes open a highway for inland countries to the sea, their sphere of influence is greatly increased. San Francisco, New York, Marseilles, Genoa, Venice, Beirut and Bombay are seaports which owe their importance in no small degree to dominant pass routes into their hinterland.

[Sidenote: Passes determine trans-montane roads.]

In plains and lowlands highways may run in any direction expediency suggests, but in mountain regions the pass points the road. In very high ranges there is no appeal from this law; but in lower systems and especially in old mountains which have been rounded and worn down by ages of denudation, economic and social considerations occasionally transcend orographical conditions in fixing the path of highways. Scarcely less important than pass or gap is the avenue of approach to the same. This is furnished by lateral or transverse valleys of erosion. The deeper their reentrant angles cut back into the heart of the highlands, the more they facilitate intercourse and lend historical importance to the pass route. The Alpine passes which are approached by a single valley from each side are those crossed by railroads to-day,—Mont Cenis, Simplon, St. Gotthard and the Brenner. The Alpine chain is trenched on its inner or southern side by a series of transverse erosion valleys, such as the Dora Baltea, Sesia, Tosa, Ticino, Adda, Adige, and Tagliamento, which carry roads up to the chief Alpine passes. The coincidence of the Roman and medieval roads over the Alps with the modern railroads is striking, except in the single point of elevation. Railroads tend to follow lower levels. Modern engineering skill enables them to tunnel the crest, to cut galleries in the perpendicular walls of gorges, and to embank mountain torrents against the spring inundation of the roadbed, where it drops to the valley floor.

[Sidenote: Navigable river approaches to passes.]

Where gaps are low and the approaching waters are navigable, at least for the small craft of early days, they combine to enhance the historical importance of their routes. The Mohawk River, navigable for the canoe of Indian and fur trader, greatly increased travel and traffic through the Mohawk depression. The Pass of Belfort is the greatest historic gateway of western Europe, chiefly because it unites the channels of the Rhone, Saone and Rhine. Lake Lucerne brings the modern tourist by boat to the foot of the railroad ascent to the St. Gotthard Pass, as the long gorge of Lake Maggiore receives him at the southern end. Lake Maggiore is the water outlet also of the Simplon Pass from the upper Rhone, the Lukmanier (6288 feet or 1917 meters) from the Hither Rhine, and the San Bernadino (6766 feet or 2063 meters) from the Hinter Rhine.[1235] This geographical fact explains the motive of Swiss expansion in the fifteenth century in embracing the Italian province of Ticino and the upper end of Lake Maggiore. A significance like that of the Swiss and Italian lakes for the Alpine passes appears emphasized in the Sogne Fiord of Norway. This carries a marine highway a hundred miles into the land; from its head, roads ascend to the only two dents in the mountain wall south of the wide snowfield of the Jotun Fjeld, and they lead thence by the valleys of Hallingdal and Valders down to the plains of Christiania.

[Sidenote: Types of settlements in the valley approaches.]

Genuine mountain passes have only emergency inhabitants—the monks and dogs of the hospice, the road-keepers in their refuge huts or cantoniere, or the garrison of a fort guarding these important thoroughfares. The flanking valleys of approach draw to themselves the human life of the mountains. Their upper settlements show a certain common physiognomy, born of their relation to the barren transit region above, except in those few mountain districts of advanced civilization where railroads have introduced through traffic over the barrier. At the foot of the final ascent to the pass, where often the carriage road ends and where mule-path or foot-trail begins, is located a settlement that lives largely by the transmontane travel. It is a place of inns, hostelries, of blacksmith shops, where in the busy season the sound of hammer and anvil is heard all night; of stables and corrals crowded with pack and draft animals; of storehouses where the traveler can provide himself with food for the journey across the barren, uninhabited heights. It is the typical outfitting point such as springs up on the margin of any pure transit region, whether mountain or desert. Such places are Andermatt and Airolo, lying at an altitude of 4000 feet or more on the St. Gotthard road, St. Moritz below the Maloja Pass, Jaca near the Pass de Canfranc over the Pyrenees, Kugiar and Shahidula[1236] at an elevation of 10,775 feet or 3285 meters on the road up to the Karakorum Pass (18,548 feet or 5655 meters), which crosses the highest range of the Himalayas between Leh in the upper Indus Valley and Yarkand in Chinese Turkestan.

[Sidenote: Lower settlements.]

Farther down the transverse valley the type of settlement changes where side valleys, leading down from other passes, converge and help build up a distributing center for a considerable highland area. Such a point is Chiavenna in northern Italy, located above the head of Lake Como at the junction of the Mera and Liro valleys, which lead respectively to the Spluegen and Maloja passes. It lies at an altitude of 1090 feet (332 meters) and has a population of 4000. Such a point is Aosta (1913 feet or 583 meters elevation) in the Dora Baltea Valley, commanding the Italian approaches to the Great St. Bernard Pass, and the less important Col de Fenetre leading to the upper Rhone, the Little St. Bernard highway to the valley of the Isere, and Col de la Seigne path around the Mont Blanc range to the valley of the Arve. Aosta was an important place in the Roman period and has to-day a population of about 8000. Kokan, in the upper Sir-Daria Valley in Russian Turkestan, commands the approach to the passes of the western Tian Shan and the northern Pamir. Its well-stocked bazaars, containing goods from Russia, Persia and India, testify to its commercial location.

[Sidenote: Pass cities and their markets.]

When the highland area is very broad and therefore necessitates long transit journeys, genuine pass cities develop at high altitudes, and become the termini of the transmontane trade. Such is the Leh (11,280 feet or 3439 meters) on the caravan route from Central Asia over the Karakorum Pass down to Kashmir, and such is Srinagar (5252 feet or 1603 meters) in Kashmir. To their markets come caravans from Chinese Turkestan, laden with carpets and brick tea, and Tibetan merchants from Lhassa, bringing wool from their highland pastures to exchange for the rice and sugar of lowland India.[1237] Leh is conveniently situated about half way between the markets of India and Central Asia. Therefore it is the terminus for caravans arriving from both regions, and exchange place for products from north and south. Seldom do caravans from either direction go farther than this point. Here the merchants rest for a month or two and barter their goods. Tents of every kind, camels, yaks, mules and horses, coolie transports of various races, men of many languages and many religions, give to this high-laid town a truly cosmopolitan stamp in the summer time when the passes are open.[1238] Kabul, which lies at an altitude of nearly 6000 feet near the head of the Kabul River, is the focus of numerous routes over the Hindu Kush, and dominates all routes converging on the northwest frontier of the Punjab.[1239] It is therefore the military and commercial key to India. Its narrow winding streets are obstructed by the picturesque kafilas of Oriental merchants, stocked with both Russian goods from the Oxus districts and British goods from India in evidence of its intermediary location.[1240]

Occasionally a very high market develops for purely local use. The Indian Himalayan province of Kumaon contains the market town of Garbyang, at an elevation of 10,300 feet or about 3000 meters, on the Kali River road leading by the Lipu Lekh Pass (16,780 feet or 5115 meters) over to Tibet. It has grown up as a trade center for the Dokpa Tibetans, who will not descend below 10,000 feet because their yak and sheep die at a lower altitude.[1241] Farther east in the Sikkim border, Darjeeling (7150 feet or 2180 meters elevation) is center of the British wool trade with Tibet.

Often the exchange point moves nearer the summit of the pass, dividing the journey more equally between the two areas of production. Here develops the temporary summer market. High up on the route between Leh and Yarkand is Sasar, a place of unroofed enclosures for the deposit of cotton, silk and other goods left there by the caravans plying back and forth between Leh and Sasar, or Sasar and Yarkand.[1242] Nearly midway on the much frequented trade route between Leh and Lhassa, at a point 15,100 feet (nearly 500 meters) above sea level, just below the Schako Pass, lies Gartok in western Tibet, in summer a busy market surrounded by a city of tents, and the summer residence of the two Chinese viceroys, who occupy the only two substantial dwellings in the place. Here at the end of August is held a great annual fair, which is attended by traders from India, Kashmir, Mongolia, Chinese Turkestan, China proper, and Lhassa; but by November the place is deserted. The traders disperse, and the few residents of Gartok, together with the viceroys, retire down the Indus Valley to the more sheltered village of Gargunza (14,140 feet or 4311 meters elevation), which represents the limits of permanent settlement in these altitudes.[1243] The Sutlej Valley route from the Punjab to Lhassa is capped near its summit at an altitude of about 5000 meters by the summer market, of Gyanema, whose numerous types of tents indicate the various homes of the traders from Lhassa to India.[1244]

[Sidenote: Pass peoples.]

Natural thoroughfares, whether river highways or mountain pass routes, draw to themselves migration, travel, trade and war. They therefore early assume historical importance. Hence we find that peoples controlling transmontane routes have always been able to exert an historical influence out of proportion to their size and strength; and that in consequence they early become an object of conquest to the people of the lowlands, as soon as these desire to control such transit routes. The power of these pass tribes is often due to the trade which they command and which compensates them for the unproductive character of their country. In the eastern Himalayas the Tomos of the Chumbi Valley are intermediaries of trade between Darjeeling and Tibet, In the western Himalayas, the Kumaon borderland of northern India, which commands some of the best passes, has made its native folk or Bhutias bold merchants who jealously monopolize the trade over the passes to the Tibetan markets. They stretch for a zone of thirty miles south of the boundary from Nepal to Garhwal along the approach to every pass, each sub-group having its particular trade route.[1245]

[Sidenote: Transit duties.]

It is always possible for such pass tribes to levy a toll or transit duty on merchandise, or in lieu of this to rob. Caesar made war upon the Veragri and Seduni, who commanded the northern end of the Great St. Bernard Pass, in order to open up the road over the Alps, which was traversed by Roman merchants magno cum periculo magnisque cum portoriis.[1246] The Salassi, who inhabited the upper Dora Baltea Valley and hence controlled the Little St. Bernard wagon road leading over to Lugdunum or Lyons, regularly plundered or taxed all who attempted to cross their mountains. On one occasion they levied a toll of a drachm per man on a Roman army, and on another plundered the treasure of Caesar himself. After a protracted struggle they were crushed by Augustus, who founded Aosta and garrisoned it with a body of Praetorian cohorts to police the highway.[1247] The Iapodes in the Julian Alps controlled the Mount Ocra or Peartree Pass, which carried the Roman wagon road from Aquileia over the mountains down to the valley of the Laibach and the Save. This strategic position they exploited to the utmost, till Augustus brought them to subjection as a preliminary to Roman expansion on the Danube.[1248]

Turning to another part of the world, we find that the Afghan tribes commanding the passes of the Suleiman Mountains have long been accustomed to impose transit duties upon caravans plying between Turkestan and India. The merchants have regularly organized themselves into bands of hundreds or even thousands to resist attack or exorbitant exactions. The Afghans have always enforced their right to collect tolls in the Khaibar and Kohat passes, and have thus blackmailed every Indian dynasty for centuries. In 1881 the British government came to terms with them by paying them an annual sum to keep these roads open.[1249] Just to the south the Gomal Pass, which carries the main traffic road over the border mountains between the Punjab and the Afghan city of Ghazni, is held by the brigand tribe of Waziris, and is a dangerous gauntlet to be run by every armed caravan passing to and from India.[1250] The Ossetes of the Caucasus, who occupy the Pass of Dariel and the approaching valleys, regularly preyed upon the traffic moving between Russia and Georgia, till the Muscovite government seized and policed the road.[1251]

[Sidenote: Strategic power of pass states.]

The strategic importance of pass peoples tends early to assume a political aspect. The mountain state learns to exploit this one advantage of its ill-favored geographical location. The cradle of the old Savoyard power in the late Middle Ages lay in the Alpine lands between Lake Geneva and the western tributaries of the Po River. This location controlling several great mountain routes between France and Italy gave the Savoyard princes their first importance.[1252] The autonomy of Switzerland can be traced not less to the citadel character of the country and the native independence of its people, than to their political exploitation of their strategic position. They profited, moreover, by the wish of their neighbors that such an important transit region between semi-tropical and temperate Europe should be held by a power too weak to obstruct its routes. The Amir of Kabul, backed by the rapacious Afridi tribes of the Suleiman Mountains, has been able to play off British India against Russia, and thereby to secure from both powers a degree of consideration not usually shown to inferior nations. Similarly in colonial America, the Iroquois of the Mohawk depression, who commanded the passway from the Hudson to the fur fields of the Northwest and also the avenue of attack upon the New York settlements for the French in Canada, were early conciliated by the English and used by them as allies, first in the French wars and afterward in the Revolution.

NOTES TO CHAPTER XV

[1186] For physical effects, see Angelo Mosso, Life of Man on the High Alps. Translated from the Italian. London, 1898.

[1187] W.Z. Ripley, Races of Europe, pp. 463-465. New York, 1899.

[1188] Strabo, Book IV, chap. VI, 3.

[1189] W.Z. Ripley, Races of Europe, pp. 31-32. New York, 1899.

[1190] Sir Thomas Holdich, India, pp. 32-33. London, 1905.

[1191] W.Z. Ripley, The Races of Europe, Map p. 439. New York, 1899.

[1192] Imperial Gazetteer of India, Vol. I, pp. 294-295. Oxford, 1907. Sir Thomas Holdich, India, relief map on p. 171 compared with linguistic map p. 201. London, 1905.

[1193] Census of India for 1901, Risley and Gait, Vol. I, Part I, p. 2. Calcutta, 1903. B.H. Baden-Powell, The Indian Village Community, pp. 40, 130, 131. London, 1896.

[1194] Count Gleichen, The Egyptian Sudan, Vol. I, pp. 184, 185, 190. London, 1905.

[1195] Gustav Nachtigal, Sahara und Sudan, Vol. III, pp. 178, 188-192. Leipzig, 1889.

[1196] Spencer and Gillen, The Northern Tribes of Central Australia, pp. 6, 13. London, 1904.

[1197] W. Deecke, Italy, p. 365. London, 1904.

[1198] Sir Thomas Holdich, India, pp. 295-296. London, 1905. G.W. Steevens, In India, pp. 202-204. New York, 1899.

[1199] Francis Younghusband, The Heart of a Continent, pp. 138, 140, 145, 272-273. London, 1904.

[1200] E. Huntington, The Pulse of Asia, p. 87. Boston, 1907.

[1201] E.C. Semple, American History and Its Geographic Conditions, pp. 184-185. Boston, 1903.

[1202] Isabella Bird Bishop, The Yangtze Valley and Beyond, Vol. II, pp. 70-72, 88, 91. London, 1900.

[1203] Francis H. Nichols, Through Hidden Shensi, pp. 170-171. New York, 1902.

[1204] Otis T. Mason, Primitive Travel and Transportation, pp. 450-454, 474-475. Smithsonian Report, Washington, 1896.

[1205] Col. George E. Church, The Acre Territory and the Caoutchouc Regions of Southwestern Amazonia, Geog. Jour. May, 1904. London.

[1206] M. Huc, Journey through the Chinese Empire, pp. 39-40. New York, 1871.

[1207] Perceval Landon, The Opening of Tibet, pp. 54-55. New York, 1905.

[1208] Jean Baptiste Tavernier, Travels in India. Vol. II, p. 264. Translated from the French of 1676. London, 1889.

[1209] E.F. Knight, Where Three Empires Meet, pp. 231, 274, 276, 286-289. London, 1897.

[1210] Census of the Philippine Islands, Vol. I, p. 544. Washington, 1905.

[1211] Joseph Partsch, Central Europe, p. 134. London, 1903.

[1212] M.S.W. Jefferson, Caesar and the Central Plateau of France, Journal of Geog., Vol. VI, p. 113. New York, 1897.

[1213] P. Vidal de la Blache, Tableau de la Geographie de la France, p. 276. Paris, 1903.

[1214] E.A. Freeman, Historical Geography of Europe, Vol. I, p. 450-453. London, 1882.

[1215] William Morris Davis, Physical Geography, p. 183. Boston, 1899.

[1216] P. Vidal de la Blache, Tableau de la Geographie de la France, p. 260, map p. 261. Paris, 1903.

[1217] Indian Census for 1901, Risley and Gait, Vol. I, Part I, pp. 1, 2, Calcutta, 1905.

[1218] Hans Helmolt, History of the World, Vol. IV, p. 479. New York, 1902.

[1219] Sir Thomas Holdich, India, p. 67, cartogram of Hindu Kush orography. London, 1905.

[1220] Ibid., pp. 102-104.

[1221] Ibid., p. 26.

[1222] J. Partsch, Central Europe, p. 27. London, 1903.

[1223] B.H. Baden-Powell, The Indian Village Community, pp. 40-45, 111, 116. London, 1896.

[1224] H.R. Mill, International Geography, pp. 394-395. New York, 1902.

[1225] Gottfried Merzbacher, Aus den Hochregionen des Kaukasus, pp. 73-78. Leipzig, 1901.

[1226] W.Z. Ripley, The Races of Europe, p. 438. New York, 1899.

[1227] Ibid., Maps pp. 143, 147, text p. 148.

[1228] E. Huntington, The Pulse of Asia, pp. 106-109. Boston, 1907.

[1229] W.Z. Ripley, The Races of Europe, pp. 249-253. New York, 1899.

[1230] Ibid., p. 282 and cartogram, p. 284.

[1231] Sir Thomas Holdich, India, p. 201. London, 1905. Imperial Gazetteer of India, Vol. I, p. 295. Oxford, 1907.

[1232] Census of India, 1901, Ethnographic Appendices, Vol. I, p. 60, by H. H. Risley, Calcutta, 1903. C. A. Sherring, Western Tibet and the British Borderland, pp. 341-353. London, 1906.

[1233] B. Lavisse, Histoire de France, Vol. II, Part 1, p. 294. Paris, 1903.

[1234] George Adam Smith, Historical Geography of the Holy Land, pp. 383, 384, 391-400, 407, 409. New York, 1897.

[1235] Wilhelm Deecke, Italy, pp. 20, 21. London, 1904.

[1236] Francis Younghusband, The Heart of a Continent, pp. 150, 194, 199. London, 1904.

[1237] E.F. Knight, Where Three Empires Meet, pp. 12, 88, 157-159, 231. London, 1897.

[1238] Ibid., pp. 173, 177.

[1239] Sir Thomas Holdich, India, map p. 85, pp. 86, 89. London, 1905.

[1240] Vambery, Reise in Mittelasien, pp. 371-375. Leipzig, 1973.

[1241] C.A. Sherring, Western Tibet and the British Borderland, p. 136. London, 1906.

[1242] O.P. Crosby, Tibet and Turkestan, pp. 112-116. New York, 1903.

[1243] Elisee Reclus, Asia, Vol. II, pp. 50-51. C.A. Sherring, Western Tibet and the British Borderland, pp. 146-148, 152, 157, 300-303. London, 1906.

[1244] Ibid., pp. 326-327.

[1245] Ibid., pp. 4, 61-64, 310-311.

[1246] Bella Gallico, Book III, chap. I.

[1247] Strabo, Book IV, chap. VI, 1, 11.

[1248] Strabo, Book IV, chap. VI, 10.

[1249] Sir Thomas Holdich, The Indian Borderland, p. 48. London, 1909.

[1250] H.R. Mill, International Geography, p. 467. New York, 1902.

[1251] Pallas, Travels Through the Southern Provinces of Russia, Vol. I, p. 431. London, 1812.

[1252] E.A. Freeman, Historical Geography of Europe, Vol. I, pp. 286-287. London, 1882.



CHAPTER XVI

INFLUENCES OF A MOUNTAIN ENVIRONMENT

[Sidenote: Zones of altitude.]

There are zones of latitude and zones of altitude. To every mountain region both these pertain, resulting in a nice interplay of geographic factors. Every mountain slope from summit to piedmont is, from the anthropo-geographical standpoint, a complex phenomenon. When high enough, it may show a graded series of contrasted complementary locations, closely interdependent grouping of populations and employments, every degree of density from congestion to vacancy, every range of cultural development from industrialism to nomadism. The southern slope of the Monte Rosa Alps, from the glacier cap at 4500 meters to the banks of the Po River, yields within certain limits a zonal epitome of European life from Lapland to the Mediterranean. The long incline from the summit of Mount Everest (8840 meters) in the eastern Himalayas, through Darjeeling down to sea level at Calcutta, comprises in a few miles the climatic and cultural range of Asia from Arctic to Tropic.

[Sidenote: Politico-economic value of varied relief.]

For the state, a territory of varied relief is highly beneficial, because it combines manifold forms of economic activity, a wide range of crops, areas of specialized production mutually interdependent. It induces a certain balance of urban and lief, rural life, which contributes greatly to the health of the state.[1253] The steep slopes of Dai Nippon, fertile only under spade tillage, will forever insure Japan the persistence of a numerous peasantry. For geological and geographical reasons, as from national motives, therefore, Japan will probably never sacrifice its farmer to its industrial class, as England has done. On the other hand, contrasted reliefs on a great territorial scale tend to invade political solidarity. Tidewater and mountain Virginia were poor running-mates for a century before the Civil War, and then the mountain region broke out of harness. Geographical contrasts made the unification of Germany difficult, and yet they have added to the economic and national strength of the Empire. The history of Switzerland shows the high Alpine cantons always maintaining a political tug of war with the cantons of the marginal plain, and always suffering a defeat which was their salvation.

[Sidenote: Relief and climate.]

The chief effect of a varied relief is a varied climate. This changes with altitude in much the same way as with latitude. Heat and absolute humidity diminish, generally speaking, as height increases, while rainfall becomes greater up to a certain level. The effect of ascending and descending currents of air is to diminish the range of temperature on mountain slopes and produce rather an oceanic type of climate. The larger and more uniform a climatic district, the more conspicuously do even slight elevations form climatic islands, like the Harz Mountains in the North German lowlands. A land of monotonous relief has a uniform climate, while a region rich in vertical articulations is rich also in local varieties of climate.[1254] A highland of considerable elevation forms a cold district in the Temperate Zone, a temperate one in the Tropics, and a moist one in a desert or steppe. Especially in arid and torrid belts does the value of elevation for human life increase.

[Sidenote: Altitude zones of economic and cultural development.]

The highlands of Mexico, South America and the Himalayan rim of India show stratified zones of tropical, temperate, and arctic climate, to which plant, animal and human life conform. The response is conspicuous in the varying density of population in the successive altitude zones. Central Asia shows a threefold cultural stratification of its population, each attended by the appropriate density, according to location in steppe, piedmont and mountain. The steppes have their scattered pastoral nomads; the piedmonts, with their irrigation streams, support sedentary agricultural peoples, concentrated at focal points in commercial and industrial towns; the higher reaches of the mountains are occupied by sparse groups of peasants and shepherds, wringing from upland pasture and scant field a miserable subsistence. The same stratification appears in the Atlas Mountains, intensified on the southern slope by the contrast between the closely populated belt of the piedmont and the wandering Tuareg tribes of the Sahara on the one hand, and the sparse Berber settlements of the Atlas highlands on the other. The long slope of Mount Kilimanjaro in German East Africa descends to a coastal belt of steppe and desert, inhabited by Swahili cattle-breeders. Its piedmont, from 1000 feet above the plain up to 2400 feet, constitutes a zone of rich irrigated plantations and gardens, densely populated by peaceful folk of mingled Bantu and Hamitic blood. At 6000 feet, where forests cease, are found the kraals, cattle, sheep and goats of the semi-nomadic Masai of doubtful Hamitic stock, who raid the coastal lowlands for cattle, and purchase all their vegetable food from the tillage belt.[1255] [See maps page 105 and 487.]



This stratification assumes marked variations in the different geographical zones. In Greenland life is restricted to the piedmont coastal belt; above this rises the desert waste of the ice fields. Norway shows a tide-washed piedmont, containing a large majority of the population; above this, a steep slope sparsely inhabited; and higher still, a wild plateau summit occupied in summer only by grazing herds or migrant reindeer Lapps. Farther south the Alps show successive tiers of rural economy, again with their appropriate density of settlement. On their lower slope is found the vineyard belt, a region of highly intensive tillage, large returns upon labor, and hence of closely distributed settlement. Above that is the zone of field agriculture, less productive and less thickly peopled. Higher still is the wide zone of hay farming and stock-raising, supporting a sparse, semi-nomadic population and characterized by villages which diminish with the altitude and cease beyond 2000 meters. On Aetna, located in the tropical Mediterranean, three girdles of altitude have long been recognized,—the girdle of agriculture, the forest belt, and the desert summit. But the tourist who ascends Aetna, passes from the coast through a zone of orange and lemon groves, which are protected by temporary matting roofs against occasional frosts; then through vineyards and olive orchards which rise to 800 meters; then through a belt of summer crops rising to 1550 meters, and varied between 1400 and 1850 meters elevation by stretches of chestnut groves, whose green expanse is broken here and there by the huts of the forest guards, the highest tenants of the mountain. From these lonely dwellings down to the sea, density of population increases regularly to a maximum of over 385 to the square mile (150 to the square kilometer) near the coast.

[Sidenote: Altitude and density belts in tropical highlands.]

In the tropical highlands of Mexico, Central and South America, on the other hand, concentration of population and its concomitant cultural development begin to appear above the 2000 meter line. Here are the chief seats of population. Mexico has three recognized altitude zones, the cold, the temperate and the hot, corresponding to plateau, high slopes and coastal piedmont up to 1000 meters or 3300 feet; but the first two contain nine-tenths of the people. While the plateau has in some sections a population dense as that of France, the lowlands are sparsely peopled by wild Indians and lumbermen. Ecuador has three-fourths of its population crowded into the plateau basins (mean elevation 8000 feet or 2500 meters), enclosed by the ranges of the Andes. Peru presents a similar distribution, with a comparatively dense population on a plateau reaching to 11,000 feet (3500 meters) or more, though its coastal belt, being healthful, dry, and fairly well supplied with irrigation streams from the Andes, is better developed than any other similar district in tropical America.[1256] In Bolivia, 72 per cent of the total population live at an altitude of 6000 to 14,000 feet, while five out of the nine most densely peopled provinces lie at elevations over 11,000 feet.[1257] [See map page 9.]

From Mexico to central Chile, the heavy rains from the trade-winds clothe the slopes with dense forests, except on the lee side of the high Andean wall of Peru and Chile, and reduce much of the piedmont to malarial swamp and jungle. The discouragement to primitive tillage found in the unequal fight with a tropical forest, the dryer, more bracing and healthful climate of the high intermontane basins, their favorable conditions for agriculture by irrigation, and their naturally defined location stimulating to early cultural development, all combined to concentrate the population of prehistoric America upon the high valleys and plateaus. In historic times these centers have persisted, because the civilized or semi-civilized districts could be best exploited by the Spanish conquerors and especially because they yielded rich mineral wealth. Furthermore, the white population which has subsequently invaded tropical America has to a predominant degree reinforced the native plateau populations, while the imported negroes and mulattoes have sought the more congenial climatic conditions found in the hot lowlands.

[Sidenote: Increasing density with motive of protection.]

The relativity of geographical advantages in different historical periods warns us against assuming in all times a sparsity of population in mountains, even when the adjoining lowlands offer many attractions of climate and soil. In ages of incessant warfare, when the motive of safety has strongly influenced distribution of population, protected mountain sites have attracted settlement from the exposed plains, and thus increased the relative density of population on the steep slopes. The corrugated plateau of Armenia and Kurdistan, located on the uneasy political frontier of Russia, Persia and Asiatic Turkey, exposed for centuries to nomadic invasion from the east, shows a sparser population on its broad intermontane plains than on the surrounding ranges. Security makes the latter the choicer places of residence. Hence they are held by the overbearing and marauding Kurds, late-comers into the land, while the older and numerically weaker Armenians cower down on the lower levels.[1258] Here is an inversion of the usual order. The militantly stronger intruders, with no taste for agriculture, have seized the safer and commanding position on the hills, descending in winter with their cattle and horses to pasture and prey upon field and granary of the valley folk, whose better soil is a questionable advantage.