The plain fact is, that Mr. Sadler has confounded the population of a city with its population “on a given space,”--a mistake which, in a gentleman who assures us that mathematical science was one of his early and favourite studies, is somewhat curious. It is as absurd, on his principle, to say that the fecundity of London ought to be less than the fecundity of Edinburgh, because London has a greater population than Edinburgh, as to say that the fecundity of Russia ought to be greater than that of England, because Russia has a greater population than England. He cannot say that the spaces on which towns stand are too small to exemplify the truth of his principle. For he has himself brought forward the scale of fecundity in towns, as a proof of his principle. And, in the very passage which we quoted above, he tells us that, if we knew how to pursue truth, or wished to find it, we “should have compared these small towns with country places, and the different classes of towns with each other.” That is to say, we ought to compare together such unequal spaces as give results favourable to his theory, and never to compare such equal spaces as give results opposed to it. Does he mean { 298}any thing by “a given space?” Or does he mean merely such a space as suits his argument? It is perfectly clear that, if he is allowed to take this course, he may prove any thing. No fact can come amiss to him. Suppose, for example, that the fecundity of New York should prove to be smaller than the fecundity of Liverpool. “That,” says Mr. Sadler, “makes for my theory. For there are more people within two miles of the Broadway of New York, than within two miles of the Exchange of Liverpool.” Suppose, on the other hand, that the fecundity of New York should be greater than the fecundity of Liverpool. “This,” says Mr. Sadler again, “is an unanswerable proof of my theory. For there are many more people within forty miles of Liverpool than within forty miles of New York.” In order to obtain his numbers, he takes spaces in any combinations which may suit him. In order to obtain his averages, he takes numbers in any combinations which may suit him. And then he tells us that, because his tables, at the first, glance, look well for his theory, his theory is irrefragably proved.