Where sea and river meet, Nature draws no sharp dividing line. Here the indeterminate boundary zone is conspicuous. The fresh water stream merges into brackish estuary, estuary into saltier inlet and inlet into briny ocean. Closely confined sea basins like the Black and Baltic, located in cool regions of slight evaporation and fed from a large catchment basin, approach in their reduced salinity the fresh water lakes and coastal lagoons in which rivers stretch out to rest on their way to the ocean. The muddy current of the Yangtze Kiang colors the Yellow Sea, and warns incoming Chinese junks of the proximity of land many hours before the low-lying shores can be discerned.630 Columbus, sailing along the Caribbean coast of South America off the Orinoco mouth, found the ocean waters brackish and surmised the presence of a large river and therefore a large continent on his left.631

The transitional form between stream and pelagic inlet found in every river mouth is emphasized where strong tidal currents carry the sea far into these channels of the land. The tides move up the St. Lawrence River 430 miles (700 kilometers) or half way between Montreal and Quebec, and up the Amazon 600 miles (1,000 kilometers). Owing to their resemblance to pelagic channels, the estuaries of the American rivers with their salty tide were repeatedly mistaken, in the period of discoveries, for the Northwest Passage to the Pacific. Newport in 1608 explored the broad sluggish course of the James River in his search for a western ocean. Henry Hudson ascended the Hudson River almost as far as Albany, before he discovered that this was no maritime pathway, like the Bosporus or Dardanelles, leading to an ulterior sea. The long tidal course of the St. Lawrence westward into the heart of the continent fed La Salle's dream of finding here a water route to the Pacific, and fixed his village of "La Chine" above the rapids at Montreal as a signpost pointing the way to the Indies and Cathay. In the same way a tidal river at the head of Cook's Inlet on the Alaskan coast was mistaken for a Northeast Passage, not by Captain Cook but by his fellow officers, on his Pacific voyage of 1776-1780; and it was followed for several days before its character as a river was established.632

Rivers have always been the great intermediaries between land and sea, for in the ocean all find their common destination. Until the construction of giant steamers in recent years, sea navigation has always passed without break into river navigation. Sailing vessels are carried by the trade wind 600 miles up the Orinoco to San Fernando. Alexander's discovery of the Indus River led by almost inevitable sequence to the rediscovery of the Eastern sea route, which in turn ran from India through the Strait of Oman and the Persian Gulf up the navigable course of the Euphrates to the elbow of the river at Thapsacus. Enterprising sea folk have always used rivers as natural continuations of the marine highway into the land. The Humber estuary and its radiating group of streams led the invading Angles in the sixth century into the heart of Britain.633 The long navigable courses of the rivers of France exposed that whole country to the depredations of the piratical Northmen in the ninth and tenth centuries. Up every river they came, up the Scheldt into Flanders, the Seine to Paris and the Marne to Meaux; up the Loire to Orleans, the Garonne to Toulouse and the Rhone to Valence.634 So the Atlantic rivers of North America formed the lines of European exploration and settlement. The St. Lawrence brought the French from the ocean into the Great Lakes basin, whose low, swampy watershed they readily crossed in their light canoes to the tributaries of the Mississippi; and scarcely had they reached the "Father of Waters" before they were planting the flag of France on the Gulf of Mexico at its mouth. The Tupi Indians of South America, a genuine water-race, moved from their original home on the Paraguay headstream of the La Plata down to its mouth, then expanded northward along the coast of Brazil in their small canoes to the estuary of the Amazon, thence up its southern tributary, the Tapajos, and in smaller numbers up the main stream to the foot of the Andes, where detached groups of the race are still found.635 So the migrations of the Carib river tribes led them from their native seats in eastern Brazil down the Xingu to the Amazon, thence out to sea and along the northern coast of South America, thence inland once more, up the Orinoco to the foot of the Andes, into the lagoon of Maracaibo and up the Magdalena. Meanwhile their settlements at the mouth of the Orinoco threw off spores of pirate colonies to the adjacent islands and finally, in the time of Columbus, to Porto Rico and Haiti.636 [See map page 101.]

So intimate is this connection between marine and inland waterways, that the historical and economic importance of seas and oceans is noticeably influenced by the size of their drainage basins and the navigability of their debouching rivers. This is especially true of enclosed seas. The only historical importance attached to the Caspian's inland basin is that inherent in the Volga's mighty stream. The Mediterranean has always suffered from its paucity of long river highways to open for it a wide hinterland. This lack checked the spread of its cultural influences and finally helped to arrest its historical development. If we compare the record of the Adriatic and the Black seas, the first a sharply walled cul de sac, the second a center of long radiating streams, sending out the Danube to tap the back country of the Adriatic and the Dnieper to draw on that of the Baltic, we find that the smaller sea has had a limited range of influence, a concentrated brilliant history, precocious and short-lived as is that of all limited areas; that the Euxine has exercised more far-reaching influences, despite a slow and still unfinished development. The Black Sea rivers in ancient times opened their countries to such elements of Hellenic culture as might penetrate from the Greek trading colonies at their mouths, especially the Greek forms of Christianity. It was the Danube that in the fourth century carried Arianism, born of the philosophic niceties of Greek thought, to the barbarians of southern Germany, and made Unitarians of the Burgundians and Visigoths of southern Gaul.637 The Dnieper carried the religion of the Greek Church to the Russian princes at Kief, Smolensk, and Moscow. Owing to the southward course of its great rivers, Russia has found the crux of her politics in the Black Sea, ever since the tenth century when the barbarians from Kiev first appeared before Constantinople. This sea has had for her a higher economic importance than the Baltic, despite the latter's location near the cultural center of western Europe.

In other seas, too, rivers play the same part of extending their tributary areas and therefore enhancing their historical significance. The disadvantages of the Baltic's smaller size and far-northern location, as compared with the Mediterranean, were largely compensated for by the series of big streams draining into it from the south, and bringing out from a vast hinterland the bulky necessaries of life. Hence the Hanseatic League of the Middle Ages, which had its origin among the southern coast towns of the Baltic from Lubeck to Riga, throve on the combined trade of sea and river.638 The mouths of the Scheldt, Rhine, Weser, Elbe and Thames long concentrated in themselves the economic, cultural and historical development of the North Sea basin. So the White Sea, despite its sub-polar location, is valuable to Russia for two reasons; it affords a politically open port, and it receives the Northern Dwina, which is navigable for river steamers from Archangel south to Vologda, a distance of six hundred miles, and carries the export trade of a large territory.639 Similarly in recent years, Bering Sea has gained unwonted commercial activity because the Yukon River serves as a waterway 1,370 miles long to the Klondike gold fields.

The geographic influence of abundant rivers navigable from the sea is closely akin to that of highly articulated coasts. The effect of the Hardanger or Sogne Fiord, admitting ocean steamers a hundred miles into the interior of Norway, is similar to that of the Elbe and Weser estuaries, which admit the largest vessels sixty miles upstream to Hamburg and Bremen. Since river inlets can, to a certain extent, supply the place of marine inlets, from the standpoint of anthropo-geographic theory and of human practice, a land dissected by navigable rivers can be grouped with one dissected by arms of the sea. South America and Africa are alike in the unbroken contour of their coasts, but strongly contrasted in the character of their rivers. Hence the two continents present the extremes of accessibility and inaccessibility. South America, most richly endowed of all the continents with navigable streams, receiving ocean vessels three thousand miles up the Amazon as far as Tabatinga in Peru, and smaller steamers up the Orinoco to the spurs of the Andes, was known in its main features to explorers fifty years after its discovery. Africa, historically the oldest of continents, but cursed with a mesa form which converts nearly every river into a plunging torrent on its approach to the sea, kept its vast interior till the last century wrapped in utmost gloom. China, amply supplied with smaller littoral indentations but characterized by a paucity of larger inlets, finds compensation in the long navigable course of the Yangtze Kiang. This river extends the landward reach of the Yellow Sea 630 miles inland to Hanchow, where ocean-going vessels take on cargoes of tea and silk for Europe and America,640 and pay for them in Mexican dollars, the coin of the coast. Hence it is lined with free ports all the way from Shanghai at its mouth to Ichang, a thousand miles up its course.641

Navigable rivers opening passages directly from the sea are obviously nature-made gates and paths into wholly new countries; but the accessibility with which they endow a land becomes later a permanent factor in its cultural and economic development, a factor that remains constantly though less conspicuously operative when railroads have done their utmost to supplant water transportation. The importance of inland waterways for local and foreign trade and intercourse has everywhere been recognized. The peoples who have long maintained preëminence among the commercial and maritime nations of the world have owed this in no small part to the command of these natural highways, which have served to give the broad land basis necessary for permanent commercial ascendency. This has been the history of England, Holland, France and the recent record of Germany. The medieval League of the Rhine Cities flourished by reason of the Rhone-Rhine highway across western Europe. The Hanseatic League, from Bruges all the way east to Russian Novgorod, owed their brilliant commercial career, not only to the favorable maritime field in the enclosed sea basins in front of them, but also to the series of long navigable rivers behind them from the Scheldt to the Neva and Volchov. Wherefore we find the League, originally confined to coast towns, drawing into the federation numerous cities located far up these rivers, such as Ghent, Cologne, Magdeburg, Breslau, Cracow, Pskof and Novgorod.642

Rivers have played the same part in expediting Russian expansion across the wide extent of Siberia. Here again a severe climate necessitated reliance on furs, the chief natural product of the country, as the basis of trade. These, as the outcome of savage economy, were gathered in from wide areas which only rivers could open up. Therefore, where the Siberian streams flatten out their upper courses east and west against the northern face of the Asiatic plateau, with low watersheds between, the Russian explorer and sable hunter struck their eastward water trail toward the Pacific. The advance, which under Yermak crossed the Ural Mountains in 1579, reached the Yenisei River in 1610 and planted there the town of Turuchansk as a sort of milestone, almost on the Arctic Circle opposite the mouth of the Lower Tunguska, a long eastern tributary. Up this they passed to the Lena in 1627, thence to Bering Sea by the Kolima and Anadyr rivers, because these arctic fields yielded sable, beaver and fox skins in greatest quantity.643 The Lena especially, from its source down to its eastern elbow at Yakutsk, that great rendezvous of Siberian fur traders, was a highway for trapper and Cossack tribute-gatherer.644 From the sources of the Yenisei in Lake Baikal to the navigable course of the Amur was a short step, taken in 1658, though the control of the river, which was claimed by China, was not secured till two hundred years later.645 [See map page 103.]

As the only highways in new countries, rivers constitute lines of least resistance for colonial peoples encroaching upon the territory of inferior races. They are therefore the geographic basis of those streamers of settlement which we found making a fringe of civilization across the boundary zone of savagery or barbarism on the typical colonial frontier. Ethnic islands of the expanding people cluster along them like iron filings on a magnetized wire. Therefore in all countries where navigable rivers have fixed the lines of expansion, as in the United States, the northern part of the Russian Empire, and the eastern or colonial border of Germany and Austria, there is a strong anthropo-geographic resemblance in the frontiers of successive decades or centuries. But in arid or semi-arid regions like South Africa, the western plains of North America, the steppes of Russian and Chinese Turkestan, the river highway motif in expansion is lost in a variety of other geographic and geologic factors, though the water of the streams still attracts trail and settlement.

A river like the Nile, lower Volga, Irtysh or Indus, rising in highlands of abundant rainfall but traversing an arid or desert land, acquires added importance because it furnishes the sole means of water travel and of irrigation. The Nile has for ages constituted the main line of intercourse between the Mediterranean and Equatorial Africa. The Tigris, Euphrates, Indus, and the Niger where it makes its great northern bend into the Sahara near Timbuctoo,646 attest the value to local fertility and commerce inherent in these rivers of the deserts and steppes. Such rivers are always oasis-makers, whether on their way to the sea they periodically cover a narrow flood-plain like that of the Nile, or one ninety miles wide, like that of the Niger's inland delta above Timbuctoo;647 or whether they emerge into a silent sea of sand, like the Murghab of Russian Turkestan, which spreads itself out to water the gardens of Merv.

Even where such rivers have a volume too scanty to float a raft, they yet point the highway, because they alone supply water for man and beast across the desert tract. The Oxus and Sir Daria have from time immemorial determined the great trade routes through Turkestan to Central Asia. The Platte, Arkansas, Cimarron and Canadian rivers fixed the course of our early western trails across the arid plains to the foot of the Rockies; and beyond this barrier the California Trail followed the long-drawn oasis formed by the Humboldt River across the Nevada Desert, the Gila River guided the first American fur-trapping explorers across the burning deserts of Arizona to the Pacific, and the succession of water-holes in the dry bed of the Mohave River gave direction to the Spanish Trail across the Mohave Desert towards Los Angeles. In the same way, Livingstone's route from the Orange River in South Africa to Lake Ngami, under the direction of native guides, ran along the margin of the Kalahari Desert up the dry bed of the Mokoko River, which still retained an irregular succession of permanent wells.648

In the trade-wind regions of the world, which are characterized by seasons of intense drought, we find rivers carrying a scant and variable amount of water but an abundance of gravel and sand; they are known in different localities as wadis, fiumares and arroyos. Their beds, dry for long periods of the year, become natural roads, paved with the gravel which the stream regularly deposits in the wet season. Local travel in Sicily, Italy649 and other Mediterranean countries uses such natural roads extensively. Trade routes across the plateau of Judea and Samaria follow the wadis, because these give the best gradient and the best footing for the ascent.650 Wadis also determine the line of caravan routes across the highlands of the Sahara. In the desert of Southwest Africa, the Khiuseb Is the first river north of the Orange to reach the Atlantic through the barrier dunes of the coast. Hence it has drawn to its valley the trade routes from a wide circle of inland points from Ot-tawe to Windhoek and Rehobeth, and given added Importance to the British coast of Walfish Bay, into which it debouches.651 But just to the north, the broad dry bed of the Swakop offered a natural wagon route into the interior, and has been utilized for the railroad of German Southwest Africa.

The historical importance of a river increases from its source toward its mouth. Its head springs, gushing from the ground, and the ramifying brooks of its highland course yield a widely distributed water supply and thereby exercise a strong influence in locating the dwellings of men; but they play no part in the great movements and larger activities of peoples. Only when minor affluents unite to form the main stream, enlarge it in its lower course by an increasing tribute of water, and extend constantly its tributary area, does a river assume real historical importance. It reaches its fullest significance at its mouth, where it joins the world's highway of the ocean. Here are combined the best geographical advantages—participation in the cosmopolitan civilization characteristic of coastal regions, opportunity for inland and maritime commerce, and a fertile alluvial soil yielding support for dense populations. The predominant importance of the debouchment stretch of a river is indicated by the presence of such cities as London, Rotterdam, Hamburg, Bremen, Bordeaux, Odessa, Alexandria, Calcutta, Rangoon, Bangkok, Hongkong, Canton, Nanking and Shanghai, Montreal and Quebec, New York, Philadelphia, New Orleans, Buenos Ayres and Montevideo. This debouchment stretch gains in practical value and hence in permanent historical importance if it is swept by a scouring tide, which enables the junction of inland and maritime routes to penetrate into the land. Even Strabo recognized this value of tidal reaches.652 Hence in tideless basins like the Baltic and Caribbean, the great river ports have to advance coastward to meet the sea; and the lower course of even mighty streams like the Volga and Nile achieve a restricted importance.653

The control of a river mouth becomes a desideratum or necessity to the upstream people. Otherwise they may be bottled up. Though history shows us countless instances of upstream expansion, nevertheless owing to the ease of downstream navigation and this increasing historical importance from source to mouth, the direction of a river's flow has often determined the course of commerce and of political expansion.

The possibility of radial expansion, which we have found to be the chief advantage of a central location, is greatly enhanced if that central location coincides with a hydrographic center of low relief. The tenth century nucleus of the Russian Empire was found about the low nodal watershed formed by the Valdai Hills, whence radiated the rivers later embodied in the Muscovite domain. Here In Novgorod at the head of the Volchov-Ladoga-Neva system, Pskof on the Velikaya, Tver at the head of the navigable Volga, Moscow on the Oka, Smolensk on the Dnieper, and Vitebsk on the Duna, were gathered the Russians destined to displace the primitive Finnish population and appropriate the wide plains of eastern Europe. Everywhere their conquests, colonization, and commercial relations have followed the downstream course of their rivers. The Dnieper carried the Rus of Smolensk and Kief to the Euxine, into contact with the Byzantine world, and brought thence religion, art, and architecture for the untutored empire of the north. The influence of the Volga has been irresistible. Down its current Novgorod traders in the twelfth century sought the commerce of the Caspian and the Orient; and later the Muscovite princes pushed their conquest of the Tartar hordes from Asia. The Northern Dwina, Onega, Mesen and Petchora have carried long narrow bands of Slav settlement northward to the Arctic Ocean. [See map page 225.] Medieval Russian trade from Hanseatic Pskof and Novgorod, and later Russian dominion followed the Narva and Neva to the Baltic. "The Dnieper made Russia Byzantine, the Volga made It Asiatic. It was for the Neva to make it European."654

In the same way, when the early French explorers and traders of Canada reached the hydrographic center of the continent about Lakes Superior and Michigan, they quickly crossed the low rim of these basins southward to the Mississippi, and northward to the Rainy Lake and Winnipeg system draining to Hudson Bay.655 While it took them from 1608 to 1659 and 1662 to penetrate upstream from Quebec to this central watershed, only nine years elapsed from the time (1673) Marquette reached the westward flowing Wisconsin River to 1682, when La Salle reached the mouth of the Mississippi.

For the western trader, the Mississippi and Ohio were preeminently downstream paths. Gravity did the work. Only small boats, laden with fine commodities of small bulk and large value, occasionally made the forty day upstream voyage from New Orleans to Louisville. Flat boats and barges that were constructed at Pittsburg for the river traffic were regularly broken up for lumber at downstream points like Louisville and New Orleans; for the traders returned overland by the old Chickasaw Trail to the Cumberland and Ohio River settlements, carrying their profits in the form of gold. The same thing happens today, as it also happened two thousand years ago, on the Tigris and Euphrates. The highlander of Armenia or northern Mesopotamia floats down the current in his skin boat or on his brushwood raft, to sell his goods and the wood forming the frame-work of his primitive craft in timberless Bagdad and Busra, as formerly in treeless Babylon. He dries out his skins, loads them on his shoulders or on a mule brought down for the purpose, and returns on foot to his highland village.656 The same preponderance of downstream traffic appears to-day in eastern Siberia. Pedlers on the Amur start in the spring from Stretensk, 2025 miles up the river, with their wares in barges, and drift down with the current, selling at the villages en route, to the river's mouth at Nikolaievsk. Here they dispose of their remaining stock and also of their barges, the lumber of which is utilized for sidewalks, and they themselves return upstream by steamer. The grain barges of western Siberia, like the coal barges of the Mississippi, even within recent decades, are similarly disposed of at the journey's end.657 The tonnage of downstream traffic on the Ohio and Mississippi to-day greatly exceeds that upstream,. The fleet of 56 coal boats, carrying about 70,000 tons, which the great towboat Sprague takes in a single trip from Louisville down to New Orleans, all return empty. Of the 15,226,805 net tons of freight shipped in 1906 on the Ohio system, 13,980,368 tons of coal, stone, sand and lumber were carried in unrigged craft, fitted chiefly for downstream traffic.658

Owing to the strong pull exerted by a river's mouth upon all its basin, current, commerce and people alike tend to reach the ocean. For a nation holding the terrestrial course of a stream, the political fate of its tidal course or mouth must always be a matter of great concern. To the early westerner of the United States, before the acquisition of the Louisiana country, it was of vital importance whether belligerent France or more amenable Spain or the Republic itself should own the mouth of the Mississippi. Germany, which holds 240 miles (400 kilometers) of the navigable Danube,659 can never be indifferent to the political ownership of its mouth, or to the fact that a great power like Russia has edged forward, by the acquisition of Bessarabia in 1878, to the northern or Kilia debouchment channel.660 Such interest shows itself in sustained efforts either to gain political control of the mouth, or to secure the neutrality of the stream by having it declared an international waterway, and thus partially to deprive the state holding its mouth of the advantages of its transit location.

The only satisfactory solution is undivided political ownership. After France pushed eastward to the Rhine in 1648, she warred for three centuries to acquire its mouth. Napoleon laid claim to Belgium and Holland on the ground that their soil had been built up by the alluvium of French rivers. Germany's conquest of Schleswig-Holstein in 1864 was significant chiefly because it dislodged Denmark from the right bank of the lower Elbe, and secured undivided control of this important estuary. The Rhine, which traverses the Empire from north to south and constitutes its greatest single trade route, gives to Germany a more vital interest in Holland than ever France had. Her most important iron and coal mines and manufacturing industries are located on this waterway or its tributaries, the Ruhr, Mosel, Saar and Main. Hence the Rhine is the great artery of German trade and outlet for her enormous exports, which chiefly reach the sea through the ports of Belgium and Holland. These two countries therefore fatten on German commerce and reduce German profits. Hence the Empire, by the construction of the Emden-Dortmund canal, aims to divert its trade from Rotterdam and Antwerp to a German port, and possibly thereby put the screw on Holland to draw her into some kind of a commercial union with Germany.661 Heinrich von Treitschke, in his "Politik," deplores the fact that the most valuable part of the great German river has fallen into alien hands, and he declares it to be an imperative task of German policy to recover the mouth of that stream, "either by a commercial or political union." "We need the entrance of Holland into our customs union as we need our daily bread."662

When the middle and upper course of a river system are shared by several nations, their common interest demands that the control of the mouth be divided, as in the case of the La Plata between Argentine and Uruguay; or held by a small state, like Holland, too weak to force the monopoly of the tidal course. The Treaty of Paris in 1856 extended the territory of Moldavia at the cost of Russia, to keep the Russian frontier away from the Danube.663 Her very presence was ominous. The temptation to giant powers to gobble up these exquisite morsels of territory is irresistible. Hence the advisability of neutralizing small states holding such locations, as in the case of Roumania; and making their rivers international waterways, as in the case of the Orinoco,664 Scheldt, Waal, Rhine and Danube.665 The Yangtze Kiang mouth, where already the treaty ports cluster thick, will probably be the first part of China to be declared neutral ground, and as such to be placed under the protection of the combined commercial powers,666 as is even now foreshadowed by the International Conservancy Board of 1910.667 The United States, by her treaty with Mexico in 1848, secured the right of free navigation on the lower or Mexican course of the Colorado River and the Gulf of California. The Franco-British convention, which in 1898 confirmed the western Sudan to France, also conceded the principle of making the Niger, the sole outlet of this vast and isolated territory, an international waterway, and created two French enclaves in British Nigeria to serve as river ports.668

The mouth of a large river system is the converging point of many lines of inland and maritime navigation. The interests of commerce, especially in its earlier periods of development, demand that the contact here of river and sea be extensive as possible. Nature suggests the way to fulfill this requirement. The sluggish lowland current of a river, on approaching sea level, throws out distributaries that reach the coast at various points and form a network of channels, which can be deepened and rendered permanent by canalization. In such regions the opportunity for the improvement and extension of waterways has been utilized from the earliest times. The ancient Egyptians, Chaldeans, East Indians, and the Gauls of the lower Po for thousands of years canaled the waters of their deltas and coastal lowlands for the combined purpose of irrigation, drainage, and navigation. The great canal system of China, constructed in the seventh century primarily to facilitate Inland intercourse between the northern and central sections of the Empire, extends from the sea at Hangchow 700 miles northward through the coastal alluvium of the Yangtze Kiang, Hoang-ho and Pie-ho to Tientsin, the port of Peking. Only the canal system of the center, important both for the irrigation of the fertile but porous loess and for the transportation of crops, is still in repair. Here the meshes of the canal network are little more than half a mile wide; farmers dig canals to their barns and bring in their produce in barges instead of hay wagons.669 Holland, where the ancient Romans constructed channels in the Rhine delta and where the debouchment courses of the Rhine, Meuse and Scheldt present a labyrinth of waterways, has to-day 1903 miles (3069 kilometers) of canals, which together with the navigable rivers, have been important geographic factors in the historical preëminence of Dutch foreign commerce. So on the lower Mississippi, in the greatest alluvial area of the United States, the government has expended large sums for the improvement of the passes and bayous of the river. The Barataria, Atchafalaya, Terrebonne, Black, Teche and Lafourche bayous have been rendered navigable, and New Orleans has been given canal outlets to the sea through Lakes Salvador, Pontchartrain and Borgne.

As the dividing channels of the lower course point to the feasibility of amplifying the connection with the ocean highway, so the spreading branches of a river's source, which approach other head waters on a low divide, suggest the extension of inland navigation by the union of two such drainage systems through canals. Where the rivers of a country radiate from a relatively low central watershed, as from the Central Plateau of France and the Valdai Hills of Russia, nature offers conditions for extensive linking of inland waterways. Hence we find a continuous passway through Russia from the Caspian Sea to the Baltic by the canal uniting the Volga and Neva rivers; another from the Black Sea up the Dnieper, which by canals finds three different outlets to the Baltic through the Vistula, Niemen and Duna.670 The Northern Dwina, linked, by canals, with the Neva through Lakes Onega and Ladoga, unites the White Sea with the Baltic.671 Sully, the great minister of Henry IV. of France, saw that the relief of the country would permit the linking of the Loire, Seine, Meuse, Saône and Rhine, and the Mediterranean with the Garonne. All his plans were carried out by his successors, but he himself, at the end of the sixteenth century, began the construction of the Briare Canal between the Loire near Orleans and the Seine at Fontainebleau.672 Similarly in the eastern half of the United States, the long, low watershed separating the drainage basin of the St. Lawrence and Great Lakes from that of the Mississippi and the Hudson made feasible the succession of canals completing the "Great Belt" of inland navigation from St. Lawrence and New York bays to the Gulf. Albert Gallatin's famous report of 1808673 pointed out the adaptation of the three low divides to canal communication; but long before this, every line of possible canoe travel by river and portage over swamp or lake-dotted watershed had been used by savages, white explorers and French voyageurs, from Lake Champlain to Lake Winnebago, so that the canal engineer had only to select from the numerous portage paths already beaten out by the moccasined feet of Indian or fur-trader.