II.  The Mons Matrona (Mont Genevre Pass, 6080 feet or 1854 meters [Transcriber’s Note:  printer’s error incorrectly printed as kilometers.]) between the headstream of the Dora Riparia and that of the Durance, which was the best highway for armies.  III.  The Little St. Bernard (7075 feet or 2157 meters), from Aosta on the Dora Baltea over to the Isere and down to Lugdunum (Lyons).  IV.  The Great St. Bernard (8109 feet or 2472 meters) route, which led northward from Aosta over the Pennine Alps to Octodurus at the elbow of the upper Rhone, where Martigny now stands.  Across the broad double rampart of the Central Alps the Roman used chiefly the Brenner route, which by a low saddle unites the deep reentrant valleys of the Adige and Inn rivers, and thus surmounts the barrier by a single pass.  However, a short cut northward over the Chalk Alps by the Fern Pass made closer connection with Augusta Vindelicorum (Augsburg).  The Romans seem to have been ignorant of the St. Gotthard, which, though high, is the summit of an unbroken ascent from Lake Maggiore up the valley of the Ticino on one side, and from Lake Lucerne up the Reuss on the other.

Mountains which spread out on a broad base in a series of parallel chains, and through which no long transverse valleys offer ready transit, form serious barriers to every phase of intercourse.  The lofty boundary wall of the Pyrenees, a folded mountain system of sharp ranges and difficult passes, has successfully separated Spain from continental Europe; it has given the Iberian Peninsula, in the course of a long history, closer relations with Morocco than with its land neighbor France.  It thus justifies the French saying that “Africa begins at the Pyrenees.”  The Andalusian fold mountains stretching across southern Spain in a double wall from Trafalgar to Cape Nao, accessible only by narrow and easily defended passes, enabled the Moors of Granada to hold their own for centuries against the Spaniard Christians.  The high thin ridges of the folded Jura system, poor in soil and sparsely populated, broken by occasional “cluses” or narrow water-gaps admitting the rivers from one elevated longitudinal valley to another, have always been a serious hindrance to traffic.[1222]

[Sidenote:  Circuitous routes through folded mountains.]

Such mountains can be crossed only by circuitous routes from pass to pass, ascending and descending each range of the system.  The Central Alps, grooved by the longitudinal valleys of the upper Rhone, Rhine and Inn, make transit travel a series of ups and downs.  The northern range must be crossed by some minor pass like the Gemmi, (7553 feet) or Panixer (7907 feet) to the longitudinal valleys, and the southern range again by the Simplon (6595 feet), San Bernadino (6768 feet), Spluegen (6946 feet) or Septimer (7582 feet) to the Po basin.  Across the corrugated highland of the Hindu Kush, lying between the plains of the Indus and the Oxus, the caravans of western Asia seek