As to the first supposition, it may be conceded that, in the course of time, a period must necessarily come when the spontaneous fertility of the newer-settled States will cease to yield grain with the same bountiful abundance it has done hitherto. But, when may that period be expected to arrive?--to what extent has exhaustion already taken place?--and what is the rate of its progress? For a reply, we have only to point to that vast territory, bounded by the lakes on the north and Ohio on the south, comprising the five States of Ohio, Indiana, Illinois, Michigan, and Wisconsin--a territory eight times the size of England and Wales, with a population about equal to that of Scotland, containing 180,000,000 acres of arable land, a large portion of which is of surprising fertility--and ask whether it is possible to believe that it has already reached the turning point of its wheat-productiveness,[1] or can by any possibility do so for centuries to come? Why, the extent of land advertised in these five States for sale, (which forms only a fraction of what still remains in the hands of government,) is greater by a fourth than the whole area of England; and of the territory that has been actually sold, it is estimated that five-sevenths is still unreclaimed from the wilderness. Then look at the means of transport provided for conveying the overflowing abundance of those rich alluvial regions to the markets of the East, by way of the two great outlets--the lakes on the north, and the Mississippi on the south. The cost of such transport is no doubt considerable; the conveyance of a quarter of wheat from the centre of Illinois to Boston, by New Orleans, averages about 16s. 6d. But, nevertheless, so trifling is the original cost of production, that immense quantities of corn do annually reach the eastern seaboard by this route, a considerable portion of which is re-shipped to Liverpool, and sold there at prices greatly below its cost of production in this country. The annexed table[2] shows the remarkable fact, that, of the whole quantity of grain exported from the United States in the five years 1842-6, twelve-thirteenths of the wheat, about one-half of the flour, and a large proportion of the Indian corn, came from the two ports of New York and Philadelphia alone. Now, as we know that these large supplies were not grown within the confines of the Eastern States, and _must_ have been brought from the westward, the inference is obvious that the two causes insisted on by Professor Johnston--the distance of the virgin soils, and the expense of transport--are as yet inoperative; or at least that they have not prevented the transmission of grain to the east in such vast quantities, as not only to meet the wants of all the population of that part of the Union, but to afford an average surplus for exportation to other countries equivalent to the annual maintenance of a million and a half of men. We need