appearance of rock formation, until we reach the isolated Mount Lambare, where basaltic rock shows itself. From Asuncion throughout Paraguay up to the Rio Appa we find, at various points, banks presenting argillaceous strata and precipitous sections of silex and limestone. On the other hand, assuming Buenos Ayres as our startingpoint, and moving northward, on the west bank of the Parana and Paraguay, we find a continuous pampa throughout the extent of thirteen degrees of latitude, interrupted only at one point, and that an isolated hill of mica schist one hundred feet in height, with a base of not more than three hundred in diameter. This occurs at the distance of about twelve miles above Asuncion, and contains the quarry which is alluded to as furnishing a good quality of stone for building. The country south of the Salado is more elevated, and apparently of older date than that north of this river, which we assume as the southern boundary of the Chaco. But the nearest approach to rock formation throughout the whole extent of this region is แ tosca," which is found in great quantities on the shores of La Plata, near the city of Buenos Ayres; at various points in both the Salado and Vermejo, it forms the beds of those rivers. Beyond, or north of the Rio Appa, the country both east and west of the RETIREMENT OF THE SEA. 439 Paraguay assumes very much the same character, low and of recent date, broken only by isolated hills, some of them rising almost to the proportions of mountains from the water's edge. At Pan de Azucar the formation is syenite; at Olimpo, basaltic rock; at Coimbra, limestone, white marble, and sandstone, with apparent impressions of moss resembling arborescent marble; at Corumba, limestone. Here we had evidently, however, entered upon a formation differing from that of the Chaco. Detached spurs and isolated ranges of mountains west of the river, divided and intersected by low flat lands, quite submerged at the season of high water, lead the imagination to picture them, at some anterior date, as islands in what we may conceive this vast region of La Plata once to have been an inland sea. From the north of Patagonia along the eastern slopes of the Andean range, skirting the pampa northward to within the Province of Chiquitos, turning east, along the sierras which divide the valley of the Amazon from that of La Plata, to the Paraguay, descending the latter to its tributary, the Appa, and ascending this to its source, following the Cordillera de Maracayn to the Salto Grande of the Parana; descending this river to Missiones, thence across to the Uruguay throughout its course, and to the capes by which the great estuary pours its waters into the Atlantic, we trace out what is supposed to have been the limits of a great gulf. Then came a gradual subsidence, and water-courses found their beds in valleys and in the gentle lowlands of the Chaco. We may regard this as a distinct period in the retirement of these waters, for as yet we suppose the sea to be far above its present shore-line. The rivers of La Plata were then born, and Sir Woodbine Parrish finds their outlet in the Callera de Arriola, where the fossil remains he procured for the British Museum were discovered. From this point, in the lapse of time, as the earth encroached upon the these riverine waters found a more extended course, and may yet, with the flight of years or ages, overflow the limits assigned them by modern geography. Strata of marine shells found at various depths attest the revolutions that have been going on for ages. And upon a vast section of the bed of this ancient sea has been formed the alluvial structure of the pampas. sea, Near the shores of La Plata marine remains are frequently visible, but as we ascend from its mouth the alluvium increases in 440 THE PAMPA COUNTRY. depth. Near Santa Fé, three hundred miles from the ocean, Mr. Darwin discovered a stratum of marine shells, over which was an alluvial bed, forty or fifty feet deep, containing remains of extinct mammalia. Then again, as he remarks, "On the cliff-bound shores of Entre Rios the line can be distinguished where the estuary mud first encroached upon the deposits of the ocean.' But in no place is this alluvial deposit more distinctly marked than upon the Vermejo, with its banks rising to the height of thirty and forty feet in the level country of the Chaco. Three beds or strata were always distinguishable; the upper and the lower varying in color and character, while the centre was at all points the same; a vein of estuary mud, ordinarily at the depth of fifteen or twenty feet below the surface, at times forming a thick deposit, at others thinning out to a mere line. At one point of the river I obtained, ten feet from the surface, from a stratum of indurated clay, a specimen which has the appearance of roots and grass, and at another we found fresh-water fossil shells of very minute size. The formation of the pampa country of La Plata has scarcely received the consideration and analysis to which its peculiar features may certainly lay claim. Travelers have noted and surmised, and writers have surmised from these, but a satisfactory treatise would seem still to be wanting, to establish with some reliability how and when occurred the physical changes in this great alluvion, some of which are of very recent date. The origin of its saline deposits is a subject of interesting inquiry. Bland, one of the United States Commissioners in 1818 to Buenos Ayres, says the pampa formation "may have been gently lifted just above the level of the ocean, and left with a surface so unbroken and so flat as not yet to have been sufficiently purified of its salt and acrid matter either by filtration or washing." It is admitted, however, that a more reasonable hypothesis for the saline impreg nation of various portions of the Chaco may be found in the washing, during the season of rains, from the extensive salt-fields in the valleys and on the eastern slopes of the Cordilleras. Hence flow the head waters of the rivers, which, by filtration or evaporation, impregnate the adjacent soil and form saline lagoons, the sources of other streams of less magnitude. We know that salts on the outer crusts of the earth have been continuously found in lowlands and highlands, in springs and pools, at considerable elevations. Shells and marine remains similar to those found throughout this SEA AND LAND CHANGES. 441 vast basin have been discovered from the tops of the Andes to the mountains of China. All creation tells of a diluvial, and again points out to us an alluvial period. That the Chaco country is an alluvial formation rests beyond a doubt. Mr. Darwin enumerates nine distinct quadrupeds, the remains of which he discovered at Bahia Blanca in the province of Buenos Ayres. The state of preservation in which they were found, and other minor circumstances, prove that they were not tossed and swallowed up by some internal convulsion of nature, but were slowly and gradually entombed by the earthy matter, still encroaching upon the sea and rescuing from its waste of waters a land of fertility. The physical revolutions the surface of the earth has been undergoing were long ago proved from the accounts of Strabo, of Herodotus, and a host of ancient writers. The land has continuously encroached upon the sea, and in turn the sea has encroached upon the land. Herodotus thought that Egypt might once have been a long and narrow gulf. There are certainly undoubted proofs here, as in many places elsewhere, of the receding of the water. Strabo discussed the possibility of the coast of Asia Minor having in course of time considerably extended itself into the sea, and Admiral Beaufort has pointed out the inlets that have been filled up and the islands that have joined to the main land since the days of that ancient geographer. Ravenna, Notre Dame des Ports, and numerous other towns, which were once sea-ports, are now several miles inland. The ancient town of Port Valois, the Portus Valesiæ of the Romans, was once situated at the mouth of the Rhine, but, from the extensive delta formed by the sediment brought down that river, now stands a mile and a half from the water. On the other hand, the temple of Serapis and other structures in the Bay of Baix are remarkable evidences of the fall of the earth and the rise of the sea. The filling up of the River La Plata and the extension of the delta of the Parana are changes that have not totally escaped observation, although they have not been noted with any degree of accuracy. Buenos Ayres may yet, like the cities just mentioned, become an inland town. The author of the Argentina, speaking of the depth of water between San Gabriel and the present site of Buenos Ayres, says, "De ancho nueve leguas o mas tiene El rio pora qui y muy hondable, 442 FERTILITY OF THE SOIL La nave hasta aqui segura viene "The river 's here nine leagues or more, As though 'twere an open sea." We are left to conjecture what the poet's notions were of the depth of water; but it is not probable that he would have applied the term "muy hondable" to eighteen or twenty feet of water, almost in an open sea; and we may fairly infer that since the period when Centenera ascended the river, about three centuries ago, the detritus brought down by its current has gradually filled up the bed to its present level. What the amount of this deposit can have been we are left to imagine. Little doubt, however, can be entertained but this filling up has been and still continues the silent work of time, and that as each day La Plata pours its sea of waters out into the ocean, layers of mud and vegetable matter sift to its shallow bottom. All the great rivers of La Plata flow from the finest mineral districts of the world; but this valley has yet richer mines in its varied and fertile soil, and in the wealth of the vegetable kingdom, which is marvelous. In ascending continuously from the Capes of La Plata to Martin Garcia, from the fragrant isles of the Parana to the fruitful wilds of Brazil, in river and land explorations of over eight thousand miles, we found every indigenous variety of tropical vegetation; passed forests of precious woods, interrupted only by extended plains carpeted with vigorous grasses and capable of supporting an incalculable number of horned cattle. Again I entered populous districts, and witnessed a demonstration of all the capabilities of the soil for agricultural wealth; but the inhabitants of these districts, not stimulated to exertion by exterior commerce, have heretofore pursued agriculture only as a means of supplying the demand for home consumption. When small fields of cotton, tobacco, and sugar are suf ficient for the wants of a few families, there is no inducement to form great plantations; but having seen these articles grown to the perfection of maturity, with but little culture, and even spontaneously, I can readily imagine that in a few years they would become staples. We brought home sections of a variety of woods, and of their indestructible qualities I had some opportunity of judging in my |