but on the west of Bas-Atrato, there is scarcely a ridge in the plain. We do not find in this country a group of interposed mountains like that which links (between Barquisimeto, Nirgua and Valencia) the eastern chain of New Grenada (that of Suma Paz and the Sierra Nevada de Merida) to the Cordillera of the shore of Venezuela. The Cordillera of the Andes, considered in its whole extent, from the rocky wall of the island of Diego Ramirez to the isthmus of Panama, is sometimes ramified into chains more or less parallel, and sometimes articulated by immense knots of mountains. We distinguish nine of those knots, and consequently an equal number of branching-points and ramifications. The latter are generally bifurcations. The Andes are twice only divided into three chains; in the knot of Huanuco, near the source of the Amazon, and the Huallaga (latitude 10 to 11 degrees) and in the knot of the Paramo de las Papas (latitude 2 degrees), near the source of the Magdalena and the Cauca. Basins, almost shut in at their extremities, parallel with the axis of the Cordillera and bounded by two knots and two lateral chains, are characteristic features of the structure of the Andes. Among these knots of mountains some, for instance those of Cuzco, Loxa and Los Pastos, comprise 3300, 1500 and 1130 square leagues, while others no less important in the eye of the geologist are confined to ridges or transversal dykes. To the latter belong the Altos de Chisinche (latitude 0 degrees 40 minutes south) and the Los Robles (latitude 2 degrees 20 minutes north), on the south of Quito and Popayan. The knot of Cuzco, so celebrated in the annals of Peruvian civilization, presents an average height of from 1200 to 1400 toises, and a surface nearly three times greater than the whole of Switzerland. The ridge of Chisinche, which separates the basins of Tacunga and Quito, is 1580 toises high, but scarcely a mile broad. The knots or groups which unite several partial chains have not the highest summits, either in the Andes or, for the most part, in the great mountain ranges of the old continent; it is not even certain that there is always in those knots a widening of the chain. The greatness of the mass, and the height so long attributed to points whence several considerable branches issue, was founded either on theoretic ideas or on false measures. The Cordilleras were compared to rivers that swell as they receive a number of tributary streams.