The Earth as Modified by Human Action

by George P. Marsh

According to Cosimo Ridolfi (Lezioni Orali, ii., p. 424), France obtains three times as much oil from the walnut as from the olive, and nearly as much as from all oleaginous seeds together. He states that the walnut bears nuts at the age of twenty years, and yields its maximum product at seventy, and that a hectare of ground, with thirty trees, or twelve to the acre, is equal to a capital of twenty-five hundred francs.

The nut of this tree is known in the United States as the "English walnut." The fruit and the wood much resemble those of the American black walnut, Juglans nigra, but for cabinet-work the American is the more beautiful material, especially when the large knots are employed. The timber or the European species, when straight-grained, and clear, or free from knots, is, for ordinary purposes, better than that of the American black walnut, but bears no comparison with the wood of the hickory, when strength combined with elasticity is required, and its nut is very inferior in taste to that of the shagbark, as well as to the butternut, which it somewhat resembles.

"The chestnut is more valuable still, for it produces on a sterile soil, which, without it, would yield only ferns and heaths, an abundant nutriment for man."—Lavergne, Economie Rurale de la France, p. 253.

I believe the varieties developed by cultivation are less numerous in the walnut than is the chestnut, which latter tree is often grafted in Southern Europe.

The chestnut crop of France was estimated in 1848 at 3,478,000 hectolitres, or 9,877,520 Winchester bushels, and valued at 13,528,000 francs, or more than two million and a half dollars. In Tuscany the annual yield is computed at about 550,000 bushels.

The Tuscan peasants think the flour of the dried chestnut not less nutritious than Indian cornmeal, and it sells at the same price, or about three cents per English pound, in the mountains, and four cents in the towns.] The maritime pine, which has proved of such immense use in fixing drifting sands in France, may perhaps be better adapted to this purpose than any of the pines of the New World, and it is of great importance for its turpentine, resin, and tar. The epicea, or common fir, Abies picea, Abies excelsa, Picea excelsa, abundant in the mountains of France and the contiguous country, is known for its product, Burgundy pitch, and, as it flourishes in a greater variety of soil and climate than almost any other spike-leaved tree, it might be well worth transplantation. [Footnote: This fir is remarkable for its tendency to cicatrize or heal over its stumps, a property which it possesses in common with some other firs, the maritime pine, and the European larch. When these trees grow in thick clumps, their roots are apt to unite by a species of natural grafting, and if one of them be felled, although its own proper rootlets die, the stump may continue, sometimes for a century, to receive nourishment from the radicles of the surrounding trees, and a dome of wood and bark of considerable thickness be formed over it. The healing is, however, only apparent, for the entire stump, except the outside ring of annual growth, soon dies, and even decays within its covering, without sending out new shoots. See Monthly Report, Department of Agriculture, for October, 1872.] The cork oak has been introduced into California and some other parts of the United States, I believe, and would undoubtedly thrive in the Southern section of the Union. [Footnote: At the age of twelve or fifteen years, the cork-tree is stripped of its outer bark for the first time. This first yield is of inferior quality, and it employed for floats for nets and buoys, or burnt for lampblack. After this, a new layer of cork, an inch or an inch and a quarter in thickness, is formed about one in ten years, and is removed in large sheets without injury to the tree, which lives a hundred and fifty years or more. According to Clave (p. 252), the annual product of a forest of cork oaks is calculated at about 660 kilogrammes, worth 150 frances, to the hectare, which, deducting expenses, leaves a profit of 100 francs. This is about equal to 250 pound weight, and eight dollars profit to the acre. The cork oaks of the national domain in Algeria cover about 500,000 acres, and are let to individuals at rates which are expected, when the whole is rented, to yield to the state revenue of about $2,000,000.

George Sand, in the Histoire de ma Vie, speaks of the cork-forests in Southern France as among the most profitable of rural possessions, and states, what I do not remember to have seen noticed elsewhere, that Russia is the best customer for cork. The large sheets taken from the trees are slit into thin plates, and used to line the walls of apartments in that cold climate. On the cultivation and management of the cork oak, see Des Incendies et de la culture du Chene-liege, in Revue das Eaux et Forets for February, 1869.] the walnut, the chestnut, the cork oak, the mulberry, the olive, the orange, the lemon, the fig, and the multitude of other trees which, by their fruit, or by other products, yield an annual revenue, nature has provided Southern Europe with a partial compensation for the loss of the native forest. It is true that these trees, planted as most of them are at such distances as to admit of cultivation, or of the growth of grass among them, are but an inadequate substitute for the thick and shady wood; but they perform to a certain extent the same offices of absorption and transpiration, they shade the surface of the ground, they serve to break the force of the wind, and on many a steep declivity, many a bleak and barren hillside, the chestnut binds the soil together with its roots, and prevents tons of earth and gravel from washing down upon the fields and the gardens. Fruit-trees are not wanting, certainly, north of the Alps. The apple, the pear, and the prune are important in the economy both of man and of nature, but they are far less numerous in Switzerland and Northern France than are the trees I have mentioned in Southern Europe, both because they are in general less remunerative, and because the climate, in higher latitudes, does not permit the free introduction of shade trees into grounds occupied for agricultural purposes. [Footnote: The walnut, the chestnut, the apple, and the pear are common to the border between the countries I have mentioned, but the range of the other trees is bounded by the Alps, and by a well-defined and sharply drawn line to the west of those mountains. From some peculiarity in the sky of Europe, cultivated plants will thrive, in Northern Italy, in Southern France, and even in Switzerland, under a depth of shade where no crop, not even grass, worth harvesting, would grow in the United States with an equally high summer temperature. Hence the cultivation of all these trees is practicable in Europe to a greater extent than would be supposed reconcilable with the interests of agriculture. Some idea of the importance of the olive orchards may be formed from the fact that Sicily alone, an island scarcely exceeding 10,000 square miles in area, of which one-third at least is absolutely barren, has exported to the single port of Marseilles more than 2,000,000 pounds weight olive-oil per year, for the last thirty years.

According to Cosimo Ridolfi, Lezioni Orali, vol. ii., p. 340, in a favorable soil and climate the average yield of oil from poorly manured trees, which compose the great majority, is six English pounds, while with the best cultivation it rises to twenty-three pounds. The annual production of olive-oil in the whole of Italy is estimated at upwards of 850,000,000 pounds, and if we allow twelve pounds to the tree, we have something more than 70,000,000 trees. The real number of trees is, however, much greater than this estimate, for in Tuscany and many other parts of Italy the average yield of oil per tree does not exceed two pounds, and there are many millions of young trees not yet in bearing. Probably we shall not exaggerate if we estimate the olive trees of Italy at 100,000,000, and as there are about a hundred trees to the acre, the quantity of land devoted to the cultivation of the olive may be taken at a million acres. Although olive-oil is much used in cookery in Italy, lard is preferred as more nutritious. Much American lard is exported to South-eastern Italy, and olive-oil is imported in return.] The multitude of species, intermixed as they are in their spontaneous growth, gives the American forest landscape a variety of aspect not often seen in the woods of Europe, and the gorgeous tints, which nature repeats from the dying dolphin to paint the falling leaf of the American maples, oaks, and ash trees, clothe the hillsides and fringe the water-courses with a rainbow splendor of foliage, unsurpassed by the brightest groupings of the tropical flora. It must be confessed, however, that both the northern and the southern declivities of the Alps exhibit a nearer approximation to this rich and multifarious coloring of autumnal vegetation than most American travellers in Europe are willing to allow; and, besides, the small deciduous shrubs which often carpet the forest-glades of these mountains are dyed with a ruddy and orange glow, which, in the distant landscape, is no mean substitute for the scarlet and crimson and gold and amber of the transatlantic woodland. [Footnote: The most gorgeous autumnal coloring I have observed in the vegetation of Europe has been in the valleys of the Durance and its tributaries in Dauphiny. I must admit that neither in variety nor in purity and brilliancy of tint, does this coloring fall much, if at all, short of that of the New England woods. But there is this difference: in Dauphiny, it is only in small shrubs that this rich painting is seen, while in North America the foliage of large trees is dyed in full splendor. Hence the American woodland has fewer broken lights and more of what painters call breadth of coloring. Besides this, the arrangement of the leafage in large globular or conical masses, affords a wider scale of light and shade, thus aiding now the gradation now the contrast of tints, and gives the American October landscape a softer and more harmonious tone than marks the humble shrubbery of the forest hillsides of Dauphiny.

Thoreau—who was not, like some very celebrated landscape critics of the present day, an outside spectator of the action and products of natural forces, but, in the old religious sense, an OBSERVER of organic nature, living, more than almost any other descriptive writer, among and with her children—had a very eloquent paper on the "Autumnal Tints" of the New England landscape.—See his Excursions, pp. 215 et seqq.

Few men have personally noticed so many facts in natural history accessible to unscientific observation as Thoreau, and yet he had never seen that very common and striking spectacle, the phosphorescence of decaying wood, until, in the latter years of his life, it caught his attention in a bivouac in the forests of Maine. He seems to have been more excited by this phenomenon than by any other described in his works. It must be a capacious eye that takes in all the visible facts in the history of the most familiar natural object.—The Maine Woods, p. 184.]