The Project Gutenberg eBook of Man and Nature, by George P. Marsh.

[101] Among the unexpected results of human action, the destruction or multiplication of fish, as well as of other animals, is a not unfrequent occurrence. I shall have occasion to mention on a following page the extermination of the fish in a Swedish river by a flood occasioned by the sudden discharge of the waters of a pond. Williams, in his History of Vermont, i, p. 149, quoted in Thompson's Natural History of Vermont, p. 142, records a case of the increase of trout from an opposite cause. In a pond formed by damming a small stream to obtain water power for a sawmill, and covering one thousand acres of primitive forest, the increased supply of food brought within reach of the fish multiplied them to that degree, that, at the head of the pond, where, in the spring, they crowded together in the brook which supplied it, they were taken by the hands at pleasure, and swine caught them without difficulty. A single sweep of a small scoopnet would bring up half a bushel, carts were filled with them as fast as if picked up on dry land, and in the fishing season they were commonly sold at a shilling (eightpence halfpenny, or about seventeen cents) a bushel. The increase in the size of the trout was as remarkable as the multiplication of their numbers.

[102] Babinet, Études et Lectures, ii, pp. 108, 110.

[103] Thompson, Natural History of Vermont, p. 38, and Appendix, p. 13. There is no reason to believe that the seal breeds in Lake Champlain, but the individual last taken there must have been some weeks, at least, in its waters. It was killed on the ice in the widest part of the lake, on the 23d of February, thirteen days after the surface was entirely frozen, except the usual small cracks, and a month or two after the ice closed at all points north of the place where the seal was found.

[104] See page 89, note, ante.

[105] According to Hartwig, the United Provinces of Holland had, in 1618, three thousand herring busses and nine thousand vessels engaged in the transport of these fish to market. The whole number of persons employed in the Dutch herring fishery was computed at 200,000.

In the latter part of the eighteenth century, this fishery was most successfully prosecuted by the Swedes, and in 1781, the town of Gottenburg alone exported 136,649 barrels, each containing 1,200 herrings, making a total of about 164,000,000; but so rapid was the exhaustion of the fish, from this keen pursuit, that in 1799 it was found necessary to prohibit the exportation of them altogether.—Das Leben des Meeres, p. 182.

In 1855, the British fisheries produced 900,000 barrels, or enough to supply a fish to every human inhabitant of the globe.

On the shores of Long Island Sound, the white fish, a species of herring too bony to be easily eaten, is used as manure in very great quantities. Ten thousand are employed as a dressing for an acre, and a single net has sometimes taken 200,000 in a day.—Dwight's Travels, ii, pp. 512, 515.

[106] The indiscriminate hostility of man to inferior forms of animated life is little creditable to modern civilization, and it is painful to reflect that it becomes keener and more unsparing in proportion to the refinement of the race. The savage slays no animal, not even the rattlesnake, wantonly; and the Turk, whom we call a barbarian, treats the dumb beast as gently as a child. One cannot live many weeks in Turkey without witnessing touching instances of the kindness of the people to the lower animals, and I have found it very difficult to induce even the boys to catch lizards and other reptiles for preservation as specimens. See Appendix, No. 19.

The fearless confidence in man, so generally manifested by wild animals in newly discovered islands, ought to have inspired a gentler treatment of them; but a very few years of the relentless pursuit, to which they are immediately subjected, suffice to make them as timid as the wildest inhabitants of the European forest. This timidity, however, may easily be overcome. The squirrels introduced by Mayor Smith into the public parks of Boston are so tame as to feed from the hands of passengers, and they not unfrequently enter the neighboring houses.

[107] A fact mentioned by Schubert—and which in its causes and many of its results corresponds almost precisely with those connected with the escape of Barton Pond in Vermont, so well known to geological students—is important, as showing that the diminution of the fish in rivers exposed to inundations is chiefly to be ascribed to the mechanical action of the current, and not mainly, as some have supposed, to changes of temperature occasioned by clearing. Our author states that, in 1796, a terrible inundation was produced in the Indalself, which rises in the Storsjö in Jemtland, by drawing off into it the waters of another lake near Ragunda. The flood destroyed houses and fields; much earth was swept into the channel, and the water made turbid and muddy; the salmon and the smaller fish forsook the river altogether, and never returned. The banks of the river have never regained their former solidity, and portions of their soil are still continually falling into the water.—Resa genom Sverge, ii, p. 51.

[108] Wittwer, Physikalische Geographie, p. 142.

[109] To vary the phrase, I make occasional use of animalcule, which, as a popular designation, embraces all microscopic organisms. The name is founded on the now exploded supposition that all of them are animated, which was the general belief of naturalists when attention was first drawn to them. It was soon discovered that many of them were unquestionably vegetable, and there are numerous genera the true classification of which is matter of dispute among the ablest observers. There are cases in which objects formerly taken for living animalcules turn out to be products of the decomposition of matter once animated, and it is admitted that neither spontaneous motion nor even apparent irritability are sure signs of animal life.

[110] See an interesting report on the coral fishery, by Sant' Agabio, Italian Consul-General at Algiers, in the Bollettino Consolare, published by the Department of Foreign Affairs, 1862, pp. 139, 151, and in the Annali di Agricoltura, Industria e Commercio, No. ii, pp. 360, 373.

[111] The fermentation of liquids, and in many cases the decomposition of semi-solids, formerly supposed to be owing purely to chemical action, are now ascertained to be due to vital processes of living minute organisms both vegetable and animal, and consequently to physiological, as well as to chemical forces. Even alcohol is stated to be an animal product. See an interesting article by Auguste Laugel on the recent researches of Pasteur, in the Revue des Deux Mondes, for September 15th, 1863.

[112] The recorded evidence in support of the proposition in the text has been collected by L. F. Alfred Maury, in his Histoire des grandes Forêts de la Gaule et de l'ancienne France, and by Becquerel, in his important work, Des climats et de l'Influence qu'exercent les Sols boisés et non boisés, livre ii, chap. i to iv.

We may rank among historical evidences on this point, if not technically among historical records, old geographical names and terminations etymologically indicating forest or grove, which are so common in many parts of the Eastern Continent now entirely stripped of woods—such as, in Southern Europe, Breuil, Broglio, Brolio, Brolo; in Northern, Brühl, -wald, -wold, -wood, -shaw, -skeg, and -skov.

[113] The island of Madeira, whose noble forests were devastated by fire not long after its colonization by European settlers, derives its name from the Portuguese word for wood.

[114] Browsing animals, and most of all the goat, are considered by foresters as more injurious to the growth of young trees, and, therefore, to the reproduction of the forest, than almost any other destructive cause. "According to Beatson's Saint Helena, introductory chapter, and Darwin's Journal of Researches in Geology and Natural History, pp. 582, 583," says Emsmann, in the notes to his translation of Foissac, p. 654, "it was the goats which destroyed the beautiful forests that, three hundred and fifty years ago, covered a continuous surface of not less than two thousand acres in the interior of the island [of St. Helena], not to mention scattered groups of trees. Darwin observes: 'During our stay at Valparaiso, I was most positively assured that sandal wood formerly grew in abundance on the island of Juan Fernandez, but that this tree had now become entirely extinct there, having been extirpated by the goats which early navigators had introduced. The neighboring islands, to which goats have not been carried, still abound in sandal wood.'"

In the winter, the deer tribe, especially the great American moose deer, subsists much on the buds and young sprouts of trees; yet—though from the destruction of the wolves or from some not easily explained cause, these latter animals have recently multiplied so rapidly in some parts of North America, that, not long since, four hundred of them are said to have been killed, in one season, on a territory in Maine not comprising more than one hundred and fifty square miles—the wild browsing quadrupeds are rarely, if ever, numerous enough in regions uninhabited by man to produce any sensible effect on the condition of the forest. A reason why they are less injurious than the goat to young trees may be that they resort to this nutriment only in the winter, when the grasses and shrubs are leafless or covered with snow, whereas the goat feeds upon buds and young shoots principally in the season of growth. However this may be, the natural law of consumption and supply keeps the forest growth, and the wild animals which live on its products, in such a state of equilibrium as to insure the indefinite continuance of both, and the perpetuity of neither is endangered until man, who is above natural law, interferes and destroys the balance.

When, however, deer are bred and protected in parks, they multiply like domestic cattle, and become equally injurious to trees. "A few years ago," says Clavé, "there were not less than two thousand deer of different ages in the forest of Fontainebleau. For want of grass, they are driven to the trees, and they do not spare them. * * It is calculated that the browsing of these animals, and the consequent retardation of the growth of the wood, diminishes the annual product of the forest to the amount of two hundred thousand cubic feet per year, * * and besides this, the trees thus mutilated are soon exhausted and die. The deer attack the pines, too, tearing off the bark in long strips, or rubbing their heads against them when shedding their horns; and sometimes, in groves of more than a hundred hectares, not one pine is found uninjured by them."—Revue des Deux Mondes, Mai, 1863, p. 157. See also Appendix, No. 21.

Beckstein computes that a park of 2,500 acres, containing 250 acres of marsh, 250 of fields and meadows, and the remaining 2,000 of wood, may keep 364 deer of different species, 47 wild boars, 200 hares, 100 rabbits, and an indefinite number of pheasants. These animals would require, in winter, 123,000 pounds of hay, and 22,000 pounds of potatoes, besides what they would pick up themselves. The natural forest most thickly peopled with wild animals would not, in temperate climates, contain, upon the average, one tenth of these numbers to the same extent of surface.

[115] Even the volcanic dust of Etna remains very long unproductive. Near Nicolosi is a great extent of coarse black sand, thrown out in 1669, which, for almost two centuries, lay entirely bare, and can be made to grow plants only by artificial mixtures and much labor.

The increase in the price of wines, in consequence of the diminution of the product from the grape disease, however, has brought even these ashes under cultivation. "I found," says Waltershausen, referring to the years 1861-'62, "plains of volcanic sand and half-subdued lava streams, which twenty years ago lay utterly waste, now covered with fine vineyards. The ashfield of ten square miles above Nicolosi, created by the eruption of 1669, which was entirely barren in 1835, is now planted with vines almost to the summits of Monte Rosso, at a height of three thousand feet."—Ueber den Sicilianischen Ackerbau, p. 19.

[116] A Relation of a Journey Begun An. Dom. 1610, lib. 4, p. 260, edition of 1627. The testimony of Sandys on this point is confirmed by that of Pighio, Braccini, Magliocco, Salimbeni, and Nicola di Rubeo, all cited by Roth, Der Vesuv., p. 9. There is some uncertainty about the date of the last eruption previous to the great one of 1631. Ashes, though not lava, appear to have been thrown out about the year 1500, and some chroniclers have recorded an eruption in the year 1306; but this seems to be an error for 1036, when a great quantity of lava was ejected. In 1139, ashes were thrown out for many days. I take those dates from the work of Roth just cited.

[117] Except upon the banks of rivers or of lakes, the woods of the interior of North America, far from the habitations of man, are almost destitute of animal life. Dr. Newberry, describing the vast forests of the yellow pine of the West, Pinus ponderosa, remarks: "In the arid and desert regions of the interior basin, we made whole days' marches in forests of yellow pine, of which neither the monotony was broken by other forms of vegetation, nor its stillness by the flutter of a bird or the hum of an insect."—Pacific Railroad Report, vol. vi, 1857. Dr. Newberry's Report on Botany, p. 37.

The wild fruit and nut trees, the Canada plum, the cherries, the many species of walnut, the butternut, the hazel, yield very little, frequently nothing, so long as they grow in the woods; and it is only when the trees around them are cut down, or when they grow in pastures, that they become productive. The berries, too—the strawberry, the blackberry, the raspberry, the whortleberry, scarcely bear fruit at all except in cleared ground.

The North American Indians did not inhabit the interior of the forests. Their settlements were upon the shores of rivers and lakes, and their weapons and other relics are found only in the narrow open grounds which they had burned over and cultivated, or in the margin of the woods around their villages.

The rank forests of the tropics are as unproductive of human aliment as the less luxuriant woods of the temperate zone. In Strain's unfortunate expedition across the great American isthmus, where the journey lay principally through thick woods, several of the party died of starvation, and for many days the survivors were forced to subsist on the scantiest supplies of unnutritious vegetables perhaps never before employed for food by man. See the interesting account of that expedition in Harper's Magazine for March, April, and May, 1855.

Clavé, as well as many earlier writers, supposes that primitive man derived his nutriment from the spontaneous productions of the wood. "It is to the forests," says he, "that man was first indebted for the means of subsistence. Exposed alone, without defence, to the rigor of the seasons, as well as to the attacks of animals stronger and swifter than himself, he found in them his first shelter, drew from them his first weapons. In the first period of humanity, they provided for all his wants: they furnished him wood for warmth, fruits for food, garments to cover his nakedness, arms for his defence."—Études sur l'Économie Forestière, p. 13.

But the history of savage life, as far as it is known to us, presents man in that condition as inhabiting only the borders of the forest and the open grounds that skirt the waters and the woods, and as finding only there the aliments which make up his daily bread.

[118] The origin of the great natural meadows, or prairies as they are called, of the valley of the Mississippi, is obscure. There is, of course, no historical evidence on the subject, and I believe that remains of forest vegetation are seldom or never found beneath the surface, even in the sloughs, where the perpetual moisture would preserve such remains indefinitely. The want of trees upon them has been ascribed to the occasional long-continued droughts of summer, and the excessive humidity of the soil in winter; but it is, in very many instances, certain that, by whatever means the growth of forests upon them was first prevented or destroyed, the trees have been since kept out of them only by the annual burning of the grass, by grazing animals, or by cultivation. The groves and belts of trees which are found upon the prairies, though their seedlings are occasionally killed by drought, or by excess of moisture, extend themselves rapidly over them when the seeds and shoots are protected against fire, cattle, and the plough. The prairies, though of vast extent, must be considered as a local, and, so far as our present knowledge extends, abnormal exception to the law which clothes all suitable surfaces with forest; for there are many parts of the United States—Ohio, for example—where the physical conditions appear to be nearly identical with those of the States lying farther west, but where there were comparatively few natural meadows. The prairies were the proper feeding grounds of the bison, and the vast number of those animals is connected, as cause or consequence, with the existence of those vast pastures. The bison, indeed, could not convert the forest into a pasture, but he would do much to prevent the pasture from becoming a forest.

There is positive evidence that some of the American tribes possessed large herds of domesticated bisons. See Humboldt, Ansichten der Natur, i, pp. 71-73. What authorizes us to affirm that this was simply the wild bison reclaimed, and why may we not, with equal probability, believe that the migratory prairie buffalo is the progeny of the domestic animal run wild?

There are, both on the prairies, as in Wisconsin, and in deep forests, as in Ohio, extensive remains of a primitive people, who must have been more numerous and more advanced in art than the present Indian tribes. There can be no doubt that the woods where such earthworks are found in Ohio were cleared by them, and that the vicinity of these fortresses or temples was inhabited by a large population. Nothing forbids the supposition that the prairies were cleared by the same or a similar people, and that the growth of trees upon them has been prevented by fires and grazing, while the restoration of the woods in Ohio may be due to the abandonment of that region by its original inhabitants. The climatic conditions unfavorable to the spontaneous growth of trees on the prairies may be an effect of too extensive clearings, rather than a cause of the want of woods. See Appendix, No. 22.

[119] In many parts of the North American States, the first white settlers found extensive tracts of thin woods, of a very park-like character, called "oak openings," from the predominance of different species of that tree upon them. These were the semi-artificial pasture grounds of the Indians, brought into that state, and so kept, by partial clearing, and by the annual burning of the grass. The object of this operation was to attract the deer to the fresh herbage which sprang up after the fire. The oaks bore the annual scorching, at least for a certain time; but if it had been indefinitely continued, they would very probably have been destroyed at last. The soil would have then been much in the prairie condition, and would have needed nothing but grazing for a long succession of years to make the resemblance perfect. That the annual fires alone occasioned the peculiar character of the oak openings, is proved by the fact, that as soon as the Indians had left the country, young trees of many species sprang up and grew luxuriantly upon them. See a very interesting account of the oak openings in Dwight's Travels, iv, pp. 58-63.

[120] The practice of burning over woodland, at once to clear and manure the ground, is called in Swedish svedjande, a participial noun from the verb att svedja, to burn over. Though used in Sweden as a preparation for crops of rye or other grain, it is employed in Lapland more frequently to secure an abundant growth of pasturage, which follows in two or three years after the fire; and it is sometimes resorted to as a mode of driving the Laplanders and their reindeer from the vicinity of the Swedish backwoodsman's grass grounds and haystacks, to which they are dangerous neighbors. The forest, indeed, rapidly recovers itself, but it is a generation or more before the reindeer moss grows again. When the forest consists of pine, tall, the ground, instead of being rendered fertile by this process, becomes hopelessly barren, and for a long time afterward produces nothing but weeds and briers.—Læstadius, Om Uppodlingar i Lappmarken, p. 15. See also Schubert, Resa i Sverge, ii, p. 375.

In some parts of France this practice is so general that Clavé says: "In the department of Ardennes it (le sartage) is the basis of agriculture. The northern part of the department, comprising the arrondissements of Rocroi and Mézières, is covered by steep wooded mountains with an argillaceous, compact, moist and cold soil; it is furrowed by three valleys, or rather three deep ravines, at the bottom of which roll the waters of the Meuse, the Semoy, and the Sormonne, and villages show themselves wherever the walls of the valleys retreat sufficiently from the rivers to give room to establish them. Deprived of arable soil, since the nature of the ground permits neither regular clearing nor cultivation, the peasant of the Ardennes, by means of burning, obtains from the forest a subsistence which, without this resource, would fail him. After the removal of the disposable wood, he spreads over the soil the branches, twigs, briars, and heath, sets fire to them in the dry weather of July and August, and sows in September a crop of rye, which he covers by a light ploughing. Thus prepared, the ground yields from seventeen to twenty bushels an acre, besides a ton and a half or two tons of straw of the best quality for the manufacture of straw hats."—Clavé, Études sur l'Économie Forestière, p. 21.

Clavé does not expressly condemn the sartage, which indeed seems the only practicable method of obtaining crops from the soil he describes, but, as we shall see hereafter, it is regarded by most writers as a highly pernicious practice.

[121] The remarkable mounds and other earthworks constructed in the valley of the Ohio and elsewhere in the territory of the United States, by a people apparently more advanced in culture than the modern Indian, were overgrown with a dense clothing of forest when first discovered by the whites. But though the ground where they were erected must have been occupied by a large population for a considerable length of time, and therefore entirely cleared, the trees which grew upon the ancient fortresses and the adjacent lands were not distinguishable in species, or even in dimensions and character of growth, from the neighboring forests, where the soil seemed never to have been disturbed. This apparent exception to the law of change of crop in natural forest growth was ingeniously explained by General Harrison's suggestion, that the lapse of time since the era of the mound builders was so great as to have embraced several successive generations of trees, and occasioned, by their rotation, a return to the original vegetation.

The successive changes in the spontaneous growth of the forest, as proved by the character of the wood found in bogs, is not unfrequently such as to suggest the theory of a considerable change of climate during the human period. But the laws which govern the germination and growth of forest trees must be further studied, and the primitive local conditions of the sites where ancient woods lie buried must be better ascertained, before this theory can be admitted upon the evidence in question. In fact, the order of succession—for a rotation or alternation is not yet proved—may move in opposite directions in different countries with the same climate and at the same time. Thus in Denmark and in Holland the spike-leaved firs have given place to the broad-leaved beech, while in Northern Germany the process has been reversed, and evergreens have supplanted the oaks and birches of deciduous foliage. The principal determining cause seems to be the influence of light upon the germination of the seeds and the growth of the young tree. In a forest of firs, for instance, the distribution of the light and shade, to the influence of which seeds and shoots are exposed, is by no means the same as in a wood of beeches or of oaks, and hence the growth of different species will be stimulated in the two forests. See Berg, Das Verdrängen der Laubwälder im Nördlichen Deutschland, 1844. Heyer, Das Verhalten der Waldbäume gegen Licht und Schatten, 1852. Staring, De Bodem van Nederland, 1856, i, pp. 120-200. Vaupell, Om Bögens Indvandring i de Danske Skove, 1857. Knorr, Studien über die Buchen-Wirthschaft, 1863.

[122] There are, in Northern Italy and in Switzerland, joint-stock companies which insure against damage by hail, as well as by fire and lightning. Between the years 1854 and 1861, a single one of these companies, La Riunione Adriatica, paid, for damage by hail in Piedmont, Venetian Lombardy, and the Duchy of Parma, above 6,500,000 francs, or nearly $200,000 per year.

[123] The paragrandine, or, as it is called in French, the paragrêle, is a species of conductor by which it has been hoped to protect the harvests in countries particularly exposed to damage by hail. It was at first proposed to employ for this purpose poles supporting sheaves of straw connected with the ground by the same material; but the experiment was afterward tried in Lombardy on a large scale, with more perfect electrical conductors, consisting of poles secured to the top of tall trees and provided with a pointed wire entering the ground and reaching above the top of the pole. It was at first thought that this apparatus, erected at numerous points over an extent of several miles, was of some service as a protection against hail, but this opinion was soon disputed, and does not appear to be supported by well-ascertained facts. The question of a repetition of the experiment over a wide area has been again agitated within a very few years in Lombardy; but the doubts expressed by very able physicists as to its efficacy, and as to the point whether hail is an electrical phenomenon, have discouraged its advocates from attempting it.

[124] Cenni sulla Importanza e Coltura dei Boschi, p. 6.

[125] Memoria sui Boschi, etc., p. 44.

[126] Travels in Italy, chap. iii.

[127] Le Alpi che cingono l'Italia, i, p. 377.

[128] "Long before the appearance of man, * * * they [the forests] had robbed the atmosphere of the enormous quantity of carbonic acid it contained, and thereby transformed it into respirable air. Trees heaped upon trees had already filled up the ponds and marshes, and buried with them in the bowels of the earth—to restore it to us after thousands of ages in the form of bituminous coal and of anthracite—the carbon which was destined to become, by this wonderful condensation, a precious store of future wealth."—Clavé, Études sur l'Économie Forestière, p. 13.

This opinion of the modification of the atmosphere by vegetation is contested.

[129] Schacht ascribes to the forest a specific, if not a measurable, influence upon the constitution of the atmosphere. "Plants imbibe from the air carbonic acid and other gaseous or volatile products exhaled by animals or developed by the natural phenomena of decomposition. On the other hand, the vegetable pours into the atmosphere oxygen, which is taken up by animals and appropriated by them. The tree, by means of its leaves and its young herbaceous twigs, presents a considerable surface for absorption and evaporation; it abstracts the carbon of carbonic acid, and solidifies it in wood, fecula, and a multitude of other compounds. The result is that a forest withdraws from the air, by its great absorbent surface, much more gas than meadows or cultivated fields, and exhales proportionally a considerably greater quantity of oxygen. The influence of the forests on the chemical composition of the atmosphere is, in a word, of the highest importance."—Les Arbres, p. 111. See Appendix, No. 23.

[130] Composition, texture and color of soil are important elements to be considered in estimating the effects of the removal of the forest upon its thermoscopic action. "Experience has proved," says Becquerel, "that when the soil is bared, it becomes more or less heated [by the rays of the sun] according to the nature and the color of the particles which compose it, and according to its humidity, and that, in the refrigeration resulting from radiation, we must take into the account the conducting power of those particles also. Other things being equal, silicious and calcareous sands, compared in equal volumes with different argillaceous earths, with calcareous powder or dust, with humus, with arable and with garden earth, are the soils which least conduct heat. It is for this reason that sandy ground, in summer, maintains a high temperature even during the night. We may hence conclude that when a sandy soil is stripped of wood, the local temperature will be raised. After the sands follow successively argillaceous, arable, and garden ground, then humus, which occupies the lowest rank. If we represent the power of calcareous sand to retain heat by 100, we have, according to Schubler,

For [silicious?] sand	95.6
" arable calcareous soil	74.8
" argillaceous earth	68.4
" garden earth	64.8
" humus	49.0

"The retentive power of humus, then, is but half as great as that of calcareous sand. We will add that the power of retaining heat is proportional to the density. It has also a relation to the magnitude of the particles. It is for this reason that ground covered with silicious pebbles cools more slowly than silicious sand, and that pebbly soils are best suited to the cultivation of the vine, because they advance the ripening of the grape more rapidly than chalky and clayey earths, which cool quickly. Hence we see that in examining the calorific effects of clearing forests, it is important to take into account the properties of the soil laid bare."—Becquerel, Des Climats et des Sols boisés, p. 137.

[131] "The Washington elm at Cambridge—a tree of no extraordinary size—was some years ago estimated to produce a crop of seven millions of leaves, exposing a surface of two hundred thousand square feet, or about five acres of foliage."—Gray, First Lessons in Botany and Vegetable Physiology, as quoted by Coultas, What may be learned from a Tree, p. 34.

[132] See, on this particular point, and on the general influence of the forest on temperature, Humboldt, Ansichten der Natur, i, 158.

[133] The radiating and refrigerating power of objects by no means depends on their form alone. Melloni cut sheets of metal into the shape of leaves and grasses, and found that they produced little cooling effect, and were not moistened under atmospheric conditions which determined a plentiful deposit of dew on the leaves of vegetables.

[134] Becquerel, Des Climats, etc., Discours Prélim. vi.

[135] Travels, i, p. 61.

[136] Le Alpi che cingono l'Italia, pp. 370, 371.

[137] Bergsöe, Reventlovs Virksomhed, ii, p. 125.

[138] Becquerel, Des Climats, etc., p. 179.

[139] Ibid., p. 116.

[140] The following well-attested instance of a local change of climate is probably to be referred to the influence of the forest as a shelter against cold winds. To supply the extraordinary demand for Italian iron occasioned by the exclusion of English iron in the time of Napoleon I, the furnaces of the valleys of Bergamo were stimulated to great activity. "The ordinary production of charcoal not sufficing to feed the furnaces and the forges, the woods were felled, the copses cut before their time, and the whole economy of the forest was deranged. At Piazzatorre there was such a devastation of the woods, and consequently such an increased severity of climate, that maize no longer ripened. An association, formed for the purpose, effected the restoration of the forest, and maize flourishes again in the fields of Piazzatorre."—Report by G. Rosa, in Il Politecnico, Dicembre, 1861, p. 614.

Similar ameliorations have been produced by plantations in Belgium. In an interesting series of articles by Baude, entitled "Les Cotes de la Manche," in the Revue des Deux Mondes, I find this statement: "A spectator placed on the famous bell tower of the cathedral of Antwerp, saw, not long since, on the opposite side of the Schelde only a vast desert plain; now he sees a forest, the limits of which are confounded with the horizon. Let him enter within its shade. The supposed forest is but a system of regular rows of trees, the oldest of which is not forty years of age. These plantations have ameliorated the climate which had doomed to sterility the soil where they are planted. While the tempest is violently agitating their tops, the air a little below is still, and sands far more barren than the plateau of La Hague have been transformed, under their protection, into fertile fields."—Revue des Deux Mondes, January, 1859, p. 277.

[141] Cenni sulla Importanza e Coltura dei Boschi, p. 31.

[142] La Provence au point de vue des Torrents et des Inondations, p. 19.

[143] Ueber die Entwaldung der Gebirge, p. 28.

[144] Becquerel, Des Climats, etc., p. 9.

[145] Salvagnoli, Rapporto sul Bonificamento delle Maremme Toscane, pp. xli, 124.

[146] Il Politecnico, Milano, Aprile e Maggio, 1863, p. 35.

[147] Salvagnoli, Memorie sulle Maremme Toscane, pp. 213, 214.

[148] Except in the seething marshes of the tropics, where vegetable decay is extremely rapid, the uniformity of temperature and of atmospheric humidity renders all forests eminently healthful. See Hohenstein's observations on this subject, Der Wald, p. 41.

There is no question that open squares and parks conduce to the salubrity of cities, and many observers are of opinion that the trees and other vegetables with which such grounds are planted contribute essentially to their beneficial influence. See an article in Aus der Natur, xxii, p. 813.

[149] Memoria sui Boschi di Lombardia, p. 45.

[150] Économie Rurale, i, p. 22.

[151] Rossmässler, Der Wald, p. 158.

[152] Ibid., p. 160.

[153] The low temperature of air and soil at which, in the frigid zone, as well as in warmer latitudes under special circumstances, the processes of vegetation go on, seems to necessitate the supposition that all the manifestations of vegetable life are attended with an evolution of heat. In the United States, it is common to protect ice, in icehouses, by a covering of straw, which naturally sometimes contains kernels of grain. These often sprout, and even throw out roots and leaves to a considerable length, in a temperature very little above the freezing point. Three or four years since, I saw a lump of very clear and apparently solid ice, about eight inches long by six thick, on which a kernel of grain had sprouted in an icehouse, and sent half a dozen or more very slender roots into the pores of the ice and through the whole length of the lump. The young plant must have thrown out a considerable quantity of heat; for though the ice was, as I have said, otherwise solid, the pores through which the roots passed were enlarged to perhaps double the diameter of the fibres, but still not so much as to prevent the retention of water in them by capillary attraction. See App. 24.