In the immense extent of land east of the Andes, comprehending more than 480,000 square sea leagues, of which 92,000 are a mountainous tract of country, no group rises to the region of perpetual snow; none even attains the height of 1400 toises. This lowering of the mountains in the eastern region of the New Continent extends as far as 60 degrees north latitude; while in the western part, on the prolongation of the Cordillera of the Andes, the highest Summits rise in Mexico (latitude 18 degrees 59 minutes) to 2770 toises, and in the Rocky Mountains (latitude 37 to 40 degrees) to 1900 toises. The insulated group of the Alleghenies, corresponding in its eastern position and direction with the Brazil group, does not exceed 1040 toises.* (* The culminant point of the Alleghenies is Mount Washington in New Hampshire, latitude 44 1/4 degrees. According to Captain Partridge its height is 6634 English feet.) The lofty summits, therefore, thrice exceeding the height of Mont Blanc, belong only to the longitudinal chain which bounds the basin of the Pacific Ocean, from 55 degrees south to 68 degrees north latitude, that is to say, the Cordillera of the Andes. The only insulated group that can be compared with the snowy summits of the equinoctial Andes, and which attains the height of nearly 3000 toises, is the Sierra de Santa Marta; it is not situated on the east of the Cordilleras, but between the prolongation of two of their branches, those of Merida and Veragua. The Cordilleras, where they bound the Caribbean Sea, in that part which we designate by the name of Coast Chain of Venezuela, do not attain the extraordinary height (2500 toises) which they reach in their prolongation towards Chita and Merida. Considering separately the groups of the east, those of the shore of Venezuela, of the Parime, and Brazil, we see their height diminish from north to south. The highest summits of each group are the Silla de Caracas (1350 toises), the peak of Duida (1300 toises), the Itacolumi and the Itambe* (900 toises). (* According to the measure of MM. Spix and Martius the Itambe de Villa de Principe is 5590 feet high.) But, as I have elsewhere observed, it would be erroneous to judge the height of a chain of mountains solely from that of the most lofty summits. The peak of the Himalayas, accurately measured, is 676 toises higher than Chimborazo (* The Peak Iewahir, latitude 30 degrees 22 minutes 19 seconds; longitude 77 degrees 35 minutes 7 seconds east of Paris, height 4026 toises, according to MM. Hodgson and Herbert.); Chimborazo is 900 toises higher than Mont Blanc; and Mont Blanc 653 toises higher than the peak of Nethou.* (* This peak, called also peak of Anethou or Malahita, or eastern peak of Maladetta, is the highest summit of the Pyrenees. It rises 1787 toises and consequently exceeds Mont Perdu by 40 toises.) These differences do not furnish the relative average heights of the Himalayas, the Andes, the Alps and the Pyrenees, that is, the height of the back of the mountains, on which arise the peaks, needles, pyramids, or rounded domes. It is that part of the back where passes are made, which furnishes a precise measure of the minimum of the height of the great chains. In comparing the whole of my measures with those of Moorcroft, Webb, Hodgson, Saussure and Ramond, I estimate the average height of the top of the Himalayas, between the meridians of 75 and 77 degrees, at 2450 toises; the Andes* (at Peru, Quito and New Grenada), at 1850 toises (* In the passage of Quindiu, between the valley of the Magdalena and that of the Rio Cauca, I found the culminant point (la Garita del Parama) to be 1798 toises; it is however, regarded as one of the least elevated. The passages of the Andes of Guanacas, Guamani and Micuipampa, are respectively 2300, 1713, and 1817 toises above sea-level. Even in 33 degrees south latitude the road across the Andes between Mendoza and Valparaiso is 1987 toises high. I do not mention the Col de l'Assuay, where I passed, near la Ladera de Cadlud, on a ridge 2428 toises high, because it is a passage on a transverse ridge joining two parallel chains.); the summit of the Alps and Pyrenees at 1150 toises. The difference of the mean height of the Cordilleras (between 5 degrees north and 2 degrees south latitude) and the Swiss Alps, is consequently 200 toises less than the difference of their loftiest summits; and in comparing the passes of the Alps, we see that their average height is nearly the same, although peak Nethou is 600 toises lower than Mont Blanc and Mont Rosa. Between the Himalaya* (* The passes of the Himalaya that lead from Chinese Tartary into Hindostan (Nitee-Ghaut, Bamsaru, etc.) are from 2400 to 2700 toises high.) and the Andes, on the contrary, (considering those chains in the limits which I have just indicated), the difference between the mean height of the ridges and that of the loftiest summits presents nearly the same proportions.
Taking an analogous view of the groups of mountains at the east of the Andes, we find the average height of the coast-chain of Venezuela to be 750 toises; of the Sierra Parime, 500 toises; of the Brazilian group, 400 toises; whence it follows that the mountains of the eastern region of South America between the tropics are, when compared to the medium elevation of the Andes, in the relation of one to three.
The following is the result of some numerical statements, the comparison of which affords more precise ideas on the structure of mountains in general.* (* The Cols or passes indicate the minimum of the height to which the ridge of the mountains lowers in a particular country. Now, looking at the principal passes of the Alps of Switzerland (Col Terret, 1191 toises, Mont Cenis, 1060 toises; Great Saint Bernard, 1246 toises; Simplon, 1029 toises; and on the neck of the Pyrenees, Benasque, 1231 toises; Pinede, 1291 toises; Gavarnic, 1197 toises; Cavarere, 1151 toises; it would be difficult to affirm that the Pyrenees are lower than the average height of the Swiss Alps.)
TABLE OF HEIGHTS OF VARIOUS RANGES.
COLUMN 1 : NAMES OF THE CHAINS OF MOUNTAINS. COLUMN 2 : THE HIGHEST SUMMITS IN TOISES. COLUMN 3 : MEAN HEIGHT OF THE RIDGE IN TOISES. COLUMN 4 : PROPORTION OF THE MEAN HEIGHT OF THE RIDGES TO THAT A THE HIGHEST SUMMITS.
Himalayas (between north latitude : 4026 : 2450 : 1 : 1.6. 30 degrees 18 minutes and 31 degrees 53 minutes, and longitude 75 degrees 23 minutes and 77 degrees 38 minutes)
Cordillera of the Andes (between : 3350 : 1850 : 1 : 1.8. latitude 5 and 2 degrees south)
Alps of Switzerland : 2450 : 1150 : 1 : 2.1.
Pyrenees : 1787 : 1150 : 1 : 1.5.
Littoral Chain of Venezuela : 1350 : 750 : 1 : 1.8.