Berghaus has applied to the chains of the Andes in Bolivia, the investigation which I published[IQ] regarding the proportion, which varies extremely in different mountain-chains, of the mountain ridge (the mean height of the passes), to the highest summits (or the culminating points). He finds,[IR] according to Pentland’s map, that the mean height of the passes in the eastern chain is 13,505, and in the western chain 14,496 feet. The culminating points are 21,285 and 22,350 feet; consequently the ratio of the height of the ridge to that of the highest summit is, in the eastern chain, as 1 : 1·57, and in the western chain as 1 : 1·54. This ratio, which is, as it were, the measure of the subterranean upheaving force, is very similar to that in the Pyrenees, but very different from the plastic form of the Alps, the mean height of whose passes is far less in comparison with the height of Mont Blanc. In the Pyrenees these ratios are as 1 : 1·43, and in the Alps as 1 : 2·09. But, according to Fitzroy and Darwin, the height of the Sahama is still surpassed by 848 feet by that of the volcano Aconcagua (south lat. 32° 39′), in the north-east of Valparaiso in Chili. The officers of the expedition of the Adventure and Beagle found, in August 1835, that the Aconcagua was between 23,000 and 23,400 feet in height. If we reckon it at 23,200 feet it is 1776 feet, higher than Chimborazo.[IS] According to more recent calculations,[IT] Aconcagua is determined to be 23,906 feet. Our knowledge regarding the systems of mountains, which, north of the parallels of 30° and 31°, are distinguished as the _Rocky Mountains_ and the _Sierra Nevada of California_, has been vastly augmented during the last few years in the astronomico-geographical, hypsometric, geognostic, and botanical departments, by the excellent works of Charles Frémont,[IU] of Dr. Wislizenus,[IV] and of Lieutenants Abert and Peck.[IW] There prevails throughout these North American works a scientific spirit deserving of the warmest acknowledgment. The remarkable plateau, referred to in p. 34, between the Rocky Mountains and the Sierra Nevada of California, which rises uninterruptedly from 4000 to 5000 French (4260 to 5330 English) feet high, and is termed the Great Basin, presents an interior closed river-system, thermal springs, and salt lakes. None of its rivers, Bear River, Carson River, and Humboldt River, find a passage to the sea. That which, by a process of induction and combination, I represented in my great map of Mexico, executed in 1804, as the Lake of Timpanogos, is the _Great Salt Lake_ of Frémont’s map. It is 60 miles long from north to south, and 40 miles broad, and it communicates with the fresh-water Lake of Utah, which lies at a higher level, and into which the Timpanogos or Timpanaozu River enters from the eastward, in lat. 40° 13′. The fact of the Lake of Timpanogos not having been placed in my map sufficiently to the north