LAND FROM THE WATERS

[IN a remarkable little book, Man and the Earth (New York, 1906), Nathaniel S. Shaler, late professor in Harvard University, surveyed broadly the resources of the earth, showing how some are inevitably diminishing, and how others may be increased and improved. In the chapter "The Unwon Lands," the subject of irrigation is treated; then comes the chapter on drainage, pp. 87-100, which is here reprinted by kind permission of the author's family and of the publishers, Fox, Duffield and Co.]

How the waters encroach on the lands. When, in the process of building the continents, their surfaces are lifted above the plane of the sea, they normally become dry land, and, unless too arid, are fit for the uses of those flowering plants on which man depends for food. There are, however, a number of accidents which serve to retain a covering of water on these fields so as to make them unsuited to the uses of the higher plant life. The land may rise irregularly, leaving the depressions on its surface which become lakes. Like depressions may be formed by the downward-sinking areas, by the process which geologists term folding. Again, glacial action, by the irregular wearing of the rocks or the curious irregular heaps of débris it leaves on the surface, creates a multitude of hollows, forming lakes, until they are converted into peat bogs. Yet again, in humid countries mosses and even reeds may by their matted vegetation hold the rainfall as in a sponge, so that even hillsides become mantled with the boggy covering. Still further, the seashores have the amphibious zone of the tides, half land and half water, where the two "elements," as the ancients termed them, strive for mastery. The result of these conditions is that, when the critic man comes to survey the lands and judge

them in general very good, he has to note that much of their fields have not effectively escaped the primal realm of the waters-that there is still much for his arts to mend.

Large area reclaimable. It is surprising how large a part of the what-we-call land is so far occupied by water as to make it in its natural state unserviceable for agriculture. In the tropical regions these areas of bog and lake are least extensive; in that realm occupying probably not more than ten per cent. of the area. But in higher latitudes and in proportion as we approach the poles a greater part of the field is permanently inundated, so that from the parallels of 40° to the limits that climate sets on agriculture somewhere near one-fourth of the land area is in its primitive condition unsuited to the uses of man and has to be won to his service by the devices of the engineer.

Drainage in Europe. In Europe, because of the antiquity and high grade of its culture, the process of winning the inundated lands to use has already gone very far, so far, indeed, that in ten centuries the aspect of the land has been greatly changed. Thus in Great Britain, at the time of Alfred the Great, near one-third of the area of the island was beset with marshes or with lands of the bog type. These impenetrable swamps appear in large measure to have formed the boundaries of the separate little kingdoms of the Heptarchy, and to have been even more effective barriers than the open The redemption of these lands probably began in Saxon times, if not earlier, but it appears to have gone forward slowly until the reign of James I, when the population of England began to press upon the means of subsistence and the work of draining the fens was rapidly carried on. As an adventurer in this business Oliver Cromwell, it is said, had his first clash with his sovereign. Along with others he had an important drainage concession from the crown, one that was peculiarly favorable for the reason that a Dutch company had failed in the same undertaking. When Cromwell was successful and in a position to profit largely by his

sea.

success, the impecunious Charles I appropriated a considerable part of his rightful gains. It is not unlikely that this action of the king had in the end to do with his discovery of the important fact that "he had a joint in his neck."

In Holland this process of reclaiming inundated lands has been carried much further than in any other country. When agriculture began in this region about the mouth of the Rhine, probably not one-tenth of the land now tilled was fit for that use. What was not covered with morasses lay beneath the level of the tide. In some fifteen hundred years the stouthearted folk have made the most signal conquest ever effected by man in this winning of a state from the waters of sea and land. Work of the same nature and hardly less extensive has been done all along the lowlands which border the North Sea and the Baltic. Thus the fields of Northeastern Europe, in Great Britain, Ireland, the Low Countries, North Germany, and Scandinavia, which now support the agriculture of at least thirty million hardy people, have been won from bogs, marshes, and the bottom of the sea-areas which in America, save in a local and unimportant way, have been quite overlooked.

Other areas to drain in Europe. The task of winning land from the waters which has been so well done in Northeastern Europe and, in some measure, throughout that so-called continent, is by no means completed. Even in Holland there are great works still under way which some time during the present century will make yet further additions of hundreds of square miles won from the shallows of the sea to its tillable fields. In Russia there are vast areas awaiting the drainage engineer to bring them to the service of men so that they may yield the food for millions of people. Even in Italy, that most ancient seat of high tillage and of crowded population, there are extensive projects for reclaiming inundated areas now under discussion. These facts show us that in the reserves of land to be won before the world is fully peopled, we have to reckon largely on the parts of it which are to be reduced to

service by drainage. This reckoning is hard to make, for the reason that outside of Europe scarcely any attention has been given to the problems of drainage, so that but an approach to the truth is attainable.

Draining the sea floor. First let us note that the most extensive of the inundated lands is the sea floor, and that from its shallower part next the land the important gains of Holland have been made. The conditions which permit such winning are very common along most seashores; an embayed area of shallow water, where the tides have a considerable rise and fall, and where the winds are constant and strong enough to serve for pumping, is always available; but the bottom of the area to be drained must afford the materials for a fertile soil, as it, in fact, very generally does. It is not imperatively necessary that the shallows lie on the shores of a tidal sea so long as windmills close set by the margin of the area to be drained will serve to lower and keep down the water; there then is only the simple question of time and cost to bring the dyke's area into tillage.

The drowned valleys. The conditions of embayed waters of no great depth, and bottoms that will be fertile when drained, are normally found about the mouths of the larger rivers. The reason for this is that a recent geological accident, the newest of all having a world-wide effect, consisted in a general rise of the sea to the extent of some hundred feet, due to the upward movement of a portion of the deepsea floor. The gain of the sea on the land led to the flooding of the valleys of the greater rivers for a long distance upward from their ancient mouths; forming such great reentrants of the sea as we have well preserved in the admirable examples of the Chesapeake and Delaware Bays. In many cases these drowned valleys have been so far filled in with delta deposits, as in the case of the Mississippi, that the alluvial plain again projects out into the sea as at its mouth and at the Nile; more commonly there is an embayment, as in the case of Mobile Bay. In any event this inundated

valley is certain to have more or less extensive areas of shallow water which, as in Holland, may be drained and turned to cultivated fields.

The work of the mangrove trees. Besides the land won from the sea by the plants which develop the marine marshes in the higher latitude, we find in the tropics a group of trees known as mangroves, which have an even more swift and effective method of capturing land in shallow embayments. These trees are fitted to grow in salt-water silt, submerged it may be by some feet at high tide. They have long runnerlike branches which, as they grow, extend outward and downward into the water of the bays until they touch the bottom, where they take root and form new crowns and stems which in like manner send their runners further seaward. In this way a mangrove swamp will speedily close over a shallow bay even if it be some miles in width, covering it with a dense low forest. While the trees are thus marching outward, their seed, long cylinders in form, with grapples at their lower end, catch on the bottom as they drift away from the plant that bore them, rapidly grow to the surface of the water, and found new plantations. Beneath the very dense growth of the mangroves the scouring action of the tides and waves is arrested and a rapid deposit of plant and animal remains takes place, so that what was sea bottom is soon lifted to the state of a fresh-water swamp. As there are numerous varieties of mangroves in the tropical regions, some of which, as in Florida, extend their range to several degrees further toward the poles, the area they occupy and the land they have won from the sea are alike great. There is no basis for a reckoning as to the extent of their work, but it is evident that in the aggregate these fields must amount to some tens of thousand square miles, all of which have been brought by these remarkable plants into the state where the engineer may easily complete the work of converting them to the uses of man.

Area reclaimable from the sea. Although the basis for computation is imperfect, it may fairly be reckoned that in