If the frontier drew from the seaboard population a certain element, and let it multiply more freely than it would have multiplied at home, the frontier must have made that element more plentiful in the American people, taken as a whole; and this, indeed, appears to be what actually occurred. No one ventures to assert that the Americans are differentiated from the original immigrating stocks by superiority in any form of talent or in any kind of sensibility; but they impress all foreign observers with their high endowment of energy, tenacity of purpose, and willingness to take risks, and these are just the qualities that are fostered and made more abundant by the wilderness. I do not maintain that life in America has added any new trait to the descendants of transplanted Europeans, nor has it filled them all with the pioneer virtues. What I do mean is that, owing to the progressive peopling of the fertile wilderness, certain valuable strains that once were represented in, say, a sixth of the population, might come to be represented in a quarter of it; and the timid, inert sort might shrivel from a fifth of the population to a tenth. Such a shifting in the numerical strength of types would account both for the large contingent of the forceful in the normal American community, and for the prevalence of the ruthless, high-pressure, get-there-at-any-cost spirit which leaves in its wake achievement, prosperity, neurasthenia, Bright's disease, heart failure, and shattered moral standards. CHAPTER II THE CELTIC IRISH From the outbreak of the Revolution until the fourth decade of the nineteenth century there was a lull in immigration. In a lifetime fewer aliens came than now debark in a couple of months. During these sixty years powerful forces of assimilation were rapidly molding a unified people out of the motley colonial population. In the fermenting West, the meeting-place of men from everywhere, elements of the greatest diversity were blending into a common American type which soon began to tinge the streams of life that ran distinct from one another in the seaboard States. Then came another epoch of vast immigration, which has largely neutralized the effect of the nationalizing forces, and has brought us into a state of heterogeneity like to that of the later colonial era. THE HIBERNIAN TIDE