But, while the British census makes no attempt at estimating the property of the people, the independent estimates of statistical writers vary hopelessly and irreconcilably. Mr. J. R. McCulloch, one of the foremost accredited writers on economic science, lays it down as a dictum, that "sixty years is the shortest time in which the capital of an old and densely-peopled country can be expected to be doubled." Yet Joseph Lowe assumes the wealth of the United Kingdom to have doubled in eighteen years, from 1823 to 1841; while George R. Porter, in his widely-accredited book on the "Progress of the Nation," and Leoni Levi, a publicist of high reputation, make out, (by combining their estimates) that the private wealth of England increased fifty per cent. in seventeen years, at which rate it would double in about twenty-nine years, instead of sixty, as laid down by Mr. McCulloch. Mr. Levi calculates the aggregate private wealth of Great Britain in 1858, at $29,178,000,000, being a fraction less than the guesses of the census enumerators at the national wealth of the United States, twelve years later, in 1870. Can one guess be said to be any nearer the fact than the other? May we not be pardoned for treating all estimates as utterly fallacious that are not based upon known facts and figures? Why do we hear so much of the "approximate correctness" of so many statistical tables, when, in point of fact, the primary data are incapable of proof, and the averages and conclusions built upon them are all assumed? "Statisticians," says one of the fraternity, "are generally held to be eminently practical people; on the contrary, they are more given to theorizing than any other class of writers; and are generally less expert in it." In the presence of such gross discrepancies as these, by statisticians of the highest repute, and among such a practical people as the English, what value can be attached to the mere estimates of wealth which have been attempted in the census of the United States? The careful Superintendent of the Census of 1870 and 1880, the late Francis A. Walker, writes concerning it: "At the best, these figures represent but the opinion of one man, or of a body of men, in the collection of material, and in the calculation of the several elements of the public wealth." And in the last Census Report for 1890, the results of the so-called "census of wealth," are cautiously submitted, "as showing in a general way a continuous increase in the wealth of the nation, the exact proportions of which cannot be measured."