has been slowly upheaved in mass, in the same gradual manner as the coasts of the Atlantic and Pacific have risen within the recent period. A multitude of facts in the structure of the Cordillera, on this view, receive a simple explanation." His conclusion is: "Daily it is forced home on the mind of the geologist that nothing, not even the wind that blows, is so unstable as the level of the crust of this earth." [Illustration: LA VENTANA.] The geological character of Argentina is tolerably uniform. The surface is a coating of sandy soil, not usually more than 2 feet thick, which is alluvial and, from a geological point of view, quite modern. In the western districts it is usually bare of vegetation, but in the east it is covered with green herbage more or less thick. Underneath this superficial covering, however, lies the true geological formation, and this consists of argillaceous earth or mud of a reddish colour and interspersed with marly rock called by the inhabitants Tosca rock. It extends to latitude 38° or thereabouts, and is the famous Pampean formation, which Darwin calls Pampean mud. The thickness of this stratum varies considerably; it may average about 40 feet, and geologically it belongs to the Quaternary epoch, otherwise called Diluvian or Post-Pliocene. Its most remarkable feature is the enormous number of mammiferous remains which are to be found embedded in this Pampean mud, and naturalists believe that it would be impossible to dig a deep trench in any direction without disinterring some of these extinct giants. Frequently perfect skeletons are discovered. These ossiferous remains are richest in the province of Buenos Aires and become somewhat less frequent in the north and west. Some observers have marvelled that such huge creatures in such vast numbers were ever able to find nourishment, but that question is not a serious difficulty, for the largest animals are by no means the most voracious, and doubtless, like elephants of to-day, their struggle for existence was not so much against hunger as against the depredations of other animals or natural catastrophes. A much greater puzzle is their disappearance. It has been suggested that they were killed off by the Glacial cold, but it is not obvious, as has been pointed out, why this visitation carried off the mastodons and spared the parrots and hummingbirds. Another theory, put forward by a savant named M. Bravard, opines that a vast simoon overwhelmed them, but such a belief, inadequate and full of difficulties, is refuted by the fact that most of the skeletons are mutilated. Had they been overwhelmed by sand storms, they would have been preserved in almost perfect condition. The notion of drought is also inadequate. Darwin remarks that it is absurd to suppose that the most terrible calamity of this sort could destroy every species from Patagonia to Behring Straits. It is impossible to suppose that prehistoric man hunted down and slew these great creatures.