nation in the mountains.  The Overhill and Middle towns, numbering together thirty-three and situated wholly in the mountains, comprised four-fifths of their fighting force in 1775, while the nine towns distributed in the flat lands of Georgia and South Carolina were small and unimportant.  The Indians themselves distinguished these two divisions of their country, the one as Otarre or mountainous, and the others as Ayrate or low.[1259] Similarly in ancient Gaul the three strongest tribes, the Sequani, Aedui, and Arverni, all had a large mountain nucleus.  The Sequani held the Jura range with part of the Saone Valley; the Aedui held the northeast corner of the Central Plateau and some lands on the Saone, while the Arverni inhabited the western and central portion of the same highland.  In a period of constant tribal migrations and war, the occupants of these high, protected locations were better able to defend themselves, and they maintained an adequate food supply by holding some of the adjoining lowland.  Archaeologists generally agree that in central and southern Italy settlement first took place in the mountains, gradually extending thence down into the plains.  The superiority of the upland climate, the more abundant rainfall, the greater security against attack offered by mountain sites, and the excellent soil for agriculture resulting from the geological make-up of the Apennines, all combined to draw thither primitive and later settlement.[1260] [See map page 559.] Similarly in Britain of the Bronze Age, before the peoples of Aryan speech began to swarm over the island, the primitive inhabitants, involved in constant clan or tribal warfare, placed their villages on the hills, and left in the indestructible terraces on their slopes the evidences of a vanished race and an outgrown social order.[1261]

[Sidenote:  Geographic conditions affecting density of mountain population.]

The advance of civilization, which brought the ancient pirate-ridden city from the inner edge of the coastal zone down to the wave-washed strand, also drew the hill town down to the plain, and the mountain population from their inaccessible strongholds to the more accessible and productive valleys.  These facts contain a hint.  The future investigation of archaeological remains in high mountain districts may reveal at considerable elevations the oldest and hence lowest strata of prehistoric development, strata which, in the more attractive valleys, have been obliterated or overlaid by later invasions of peoples and cultures.  Ignoring this temporary attraction of population to protected mountain locations in ages of persistent warfare, we find that a comparison of many countries reveals a decreasing food supply and decreasing density of population, with every increase of height above a certain altitude, except in favored mining regions and in some tropical lands, where better climatic conditions and freedom from malaria distribute settlements far above the steaming and forest-choked lowlands.  The density of population in mountains is influenced also by the composition of the soil, which affects its fertility; by the grade and exposure of the slopes, which determine the ease and success of tillage; by the proximity of the highlands to teeming centers of lowland population, and by the general economic development of the people.