The line of argument by which, in general, all writers such as those to whom reference was made above have reached their conclusions is as follows. The population of the United States at the time it became a nation was almost wholly of native origin. It was a homogeneous people, of one stock, one language, and one set of traditions, customs, and beliefs. For the first forty years of our national life the increase of population was phenomenal, doubling every twenty-two or twenty-three years. Malthus chose the North American colonies as an example of the extreme possibilities of increase under favorable conditions, and the rate continued for many years after they ceased to be colonies. Between 1790 and 1830 the population increased from less than 4,000,000 to nearly 13,000,000, or 227 per cent in forty years. An estimate made in 1815, based on the first three censuses, reckoned the probable population of the United States in 1900 at 100,235,985. The fact that it was, instead, only 76,303,387, in spite of the incoming of 19,115,221 aliens since 1820, shows that there must have been a tremendous falling-off in the native birth rate. Careful study reveals the fact that the birth rate first began to decline appreciably about 1830, just the period when the effects of immigration first began to be strongly felt in this country, and that it diminished progressively with the swelling volume of the immigration current. Moreover, it was in just those sections where the immigrants congregated most thickly that the fall in the native birth rate was most pronounced, even down to such minor divisions as counties. New England, which, at the time of the Revolution, held the most homogeneous population in the country, and had the highest birth rate, has now the greatest proportion of foreigners and, as far as the natives at least are concerned, the lowest birth rate. To such an extent has this decline gone, that at the present time the native stock in large sections of New England is not even maintaining itself. Coincidences of time and place between the phenomena of immigration and those of the declining birth rate are so numerous and so striking that, in the words of General Walker, they “constitute a statistical demonstration such as is rarely attained in regard to the operation of any social or economic force.”