Berghaus has applied to the eastern and western chains of the Andes of Bolivia the investigation published by me in the Annales des Sciences Naturelles, T. iv. 1825, p. 225-253, of the proportion (very different in different mountain chains), which the general height of the ridge, the crest, or kamm (the mean height of the passes), bears to the highest summits or culminating points. He finds, following Pentland’s map, the mean height of the passes in the eastern chain 12672 French, or 13502 English feet; and in the western chain 13602 French, or 14896 English feet. The culminating points are 19972 and 20971 French, 21286 and 22350 English feet; consequently the ratio of the height of the ridge to that of the culminating point is, in the eastern chain, as 1 : 1.57, and in the western chain as 1 : 1.54. (Berghaus, Zeitschrift für Erdkunde, Band. ix. S. 322-326). This ratio, which is, as it were, the measure of the subterranean elevating force, is very similar to that which exists in the Pyrenees, but very different from the Alps, where the mean height of the passes is less as compared with Mont Blanc. The ratios are, in the Pyrenees, = 1 : 1.43, and in the Alps, = 1 : 2.09. But, according to Fitz Roy and Darwin, the height of the Sahama is still surpassed by 796 French, or 850 English feet, by that of the volcano of Aconcagua, on the north east of Valparaiso, in Chili, in S. lat. 32° 39′. The officers of the Adventure and Beagle, in Fitz Roy’s Expedition, found, in August 1835, the summit of Acongagua between 23000 and 23400 English feet. If we take it at 23200 (equal to 21767 Paris feet), this volcano would be 1667 French, or 1777 English, feet higher than the Chimborazo. (Fitz Roy, Voyages of the Adventure and Beagle, 1839, Vol. ii. p. 481; Darwin, Journal of Researches, 1845, pp. 223 and 291.) According to more recent calculations, the height of Acongagua is given as 22431 French, or 23907 English feet. (Mary Somerville, Physical Geogr. 1849, Vol. ii. p. 425.)