The growth is more apparent, or, in other words, the border zone is widest and most irregular, where a superior people intrudes upon the territory of an interior race.  Such was the broad zone of thinly scattered farms and villages amid a prevailing wilderness and hostile Indian tribes which, in 1810 and 1820, surrounded our Trans-Allegheny area of continuous settlement in a one to two hundred mile wide girdle.  Such has been the wide, mobile frontier of the Russian advance in Siberia and until recently in Manchuria, which aimed to include within a dotted line of widely separated railway-guard stations, Cossack barracks, and penal colonies, the vast territory which later generations were fully to occupy.  Similar, too, is the frontier of the Dutch and English settlements in South Africa, which has been pushed forward into the Kaffir country—­a broad belt of scattered cattle ranches and isolated mining hives, dropped down amid Kaffir hunting and grazing lands.  Broader still was that shadowy belt of American occupation which for four decades immediately succeeding the purchase of Louisiana stretched in the form of isolated fur-stations, lonely trappers’ camps, and shifting traders’ rendezvous from the Mississippi to the western slope of the Rockies and the northern watershed of the Missouri, where it met the corresponding nebulous outskirts of the far-away Canadian state on the St. Lawrence River.

The same process with the same geographical character has been going on in the Sahara, as the French since 1890 have been expanding southward from the foot of the Atlas Mountains in Algeria toward Timbuctoo at the cost of the nomad Tuaregs.  Territory is first subdued and administered by the military till it is fully pacified.  Then it is handed over to the civil government.  Hence the advancing frontier consists of a military zone of administration, with a civil zone behind it, and a weaker wavering zone of exploration and scout work before it.[337] Lord Curzon in his Romanes lecture describes the northwest frontier of India as just such a three-ply border.

[Sidenote:  Economic factors in expanding frontiers.]

The untouched resources of such new countries tempt to the widespread superficial exploitation, which finds its geographical expression in a broad, dilating frontier.  Here the man-dust which is to form the future political planet is thinly disseminated, swept outward by a centrifugal force.  Furthermore, the absence of natural barriers which might block this movement, the presence of open plains and river highways to facilitate it, and the predominance of harsh conditions of climate or soil rendering necessary a savage, extensive exploitation of the slender resources, often combine still further to widen the frontier zone.  This was the case in French Canada and till recent decades in Siberia, where intense cold and abundant river highways stimulated the fur trade to the practical exclusion of all other activities, and substituted