In more advanced states of society a like cause leads the surplus population of a civilised state to overflow into new lands, where there is more space, or the soil is more fertile. Thus the inhabitants of Southwestern Scotland, partly, no doubt, at the suggestion of their rulers, crossed over into Ulster, where they occupied the best lands, driving the aboriginal Celts into the rougher and higher districts, where their descendants remain in the glens of Antrim, and in the hilly parts of Down, Derry, and Tyrone. Thus the men of New England moved out to the West and settled in the Mississippi Valley, while the men of Virginia crossed the Alleghanies into Kentucky. Thus the English have colonised Canada and Australia and New Zealand and Natal. Thus the Russians have spread out from their ancient homes on the upper courses of the Dnieper and the Volga all over the vast steppes that stretch to the Black Sea and the Caucasus, as well as into the rich lands of Southwestern Siberia. Thus the surplus peasantry of Germany has gone not only to North America, but also to Southern Brazil and the shores of the Rio de la Plata. [Sidenote: The Need of Native Labour] In another form it is the excess of population over means of subsistence at home that has produced the remarkable outflow of the Chinese through the Eastern Archipelago and across the Pacific into North America, and that has carried the Japanese to the Hawaiian Islands. And here we touch another cause of migration which is indirectly traceable to Nature--namely, the demand in some countries for more labour or cheaper labour than the inhabitants of the country are able or willing to supply. Sometimes this demand is attributable to climatic causes. The Spaniards and Portuguese and English in the New World were unfitted by their physical constitutions for out-of-door labour under a tropical sun. Hence they imported negroes during the sixteenth and two following centuries in such numbers that there are now about eight millions of coloured people in the United States alone, and possibly (though no accurate figures exist) as many more in the West Indies and South America. To a much smaller extent the same need for foreign labour has recently brought Indian coolies to the shores of the Caribbean Sea, and to the hottest parts of Natal, as it brings Polynesians to the sugar plantations of Northern Queensland. [Sidenote: What Determines Race Movements]