The Alps form a great mountain range, consisting of a main chain, with ramifications, and of several parallel minor chains. They thus form a single connected whole as contrasted with the plains at their base, and nature has made no breaks therein, save at the spots where they sink to comparatively low depressions or passes. But for the sake of practical convenience it has long been usual to select certain of the best marked of these passes to serve as limits within the range, whether to distinguish several great divisions from each other, or to further break up each of these great divisions into smaller groups. As these divisions, great or small, are so to speak artificial, several systems have been proposed according to which the Alps may be divided.
We give below that which seems to us to be the most satisfactory (based very largely on personal acquaintance with most parts of the range), considering, as in the case of the limits of the chain, only its topographical aspect, as it exists at the present day, while leaving it to geologists, botanists and zoologists to elaborate special divisions as required by these various sciences.
Our selected divisions relate only to the High Alps between the Col de Tenda and the route over the Radstadter Tauern, while in each of the 18 subdivisions the less elevated outlying peaks are regarded as appendages of the higher group within the topographical limits of which they rise. We do not attempt to give a complete catalogue of the peaks and passes of the Alps, while in the case of the peaks the culminating point of a lower half-detached group has been included rather than the loftier spurs of the higher and main group; in the case of the passes, the villages or valleys they connect have been indicated, and also the general character of the route over each pass.
As regards the main divisions, three are generally distinguished; the Western Alps (chiefly French and Italian, with a small portion of the Swiss Valais (Canton Wallis)) being held to extend from the Col de Tenda to the Simplon Pass, the Central Alps (all but wholly Swiss and Italian) thence to the Reschen Scheideck Pass, and the Eastern Alps (wholly Austrian and Italian, save the small Bavarian portion at the northwest angle) thence to the Radstadter Tauern route, with a bend outwards towards the south-east, as explained under (2) in order to include the higher summits of the Southeastern Alps. Strictly speaking, we should follow the Reschen Scheideck route down the Adige Valley, but as this would include in the Central Alps the Ortler and some other of the highest Tirolese summits, it is best (remembering the artificial character of the division) to draw a line from Mals southwards either over the Umbrail Pass (the old historical pass) or the Stelvio (well known only since the carriage road was built over it in the first quarter of the 19th century) to the head of the Valtellina, and then over the Aprica Pass (as the Bergamasque Alps properly belong to the Central Alps) to the Oglio valley or the Val Camonica, and down that valley to the Lake of Iseo and Brescid.
Assuming these three main divisions, we can consider in detail the 18 sub-divisions which we distinguish; the first five forming the Western Alps, the next seven the Central Alps, and the rest the Eastern Alps, the heights throughout being given in English feet and representing the latest measurements.
See also: Principal passes of the Alps