The secret of this enormous increase was the habit that the Irish peasantry had begun to learn early in the 17th century of living upon potatoes. From that dietetic peculiarity, it is well known, much of the economic and political history of Ireland depends. At the time when it was losing its tribal organization (rather late in the day, although not so late as in the Highlands of Scotland), the country was in a fair way to pass from the pastoral state to the agricultural and industrial. It is conceivable that, if Ireland had peacefully become an agricultural country, wheaten bread would have become the staple food of the people, as in England in early times and again in later times; or that the standard might have been oatmeal in the northern province, as in Scotland: in which case one may be sure that the population would not have increased as it did. “Since the culture of the potatoes was known,” says a topographer of Kerry in 1756, “which was not before the beginning of the last century, the herdsmen find out small dry spots to plant a sufficient quantity of those roots in for their sustenance, whereby considerable tracts of these mountains are grazed and inhabited, which could not be done if the herdsmen had only corn to subsist on[461].” Twenty years later Arthur Young found an enormous extension of potato culture, the pigs being fed on the surplus crop[462]. The motive, on the part of the landlord or the farmer, was to have the peat bogs on the hill-sides reclaimed by the spade; the surface of peat having been removed, a poor subsoil was exposed, which might be made something of after it had grown several crops of potatoes, but hardly in any other way. Another motive was political; namely, the multiplication by landlords of forty-shilling freeholder dependent votes among the Catholics as soon as they became free to exercise the franchise[463]. Malthus relied so much upon statistics, that he found the case of Ireland, notable though it was, little suited to his method, and dismissed it in a few sentences. But he indicated correctly the grand cause of over-population: “I shall only observe, therefore, that the extended use of potatoes has allowed of a very rapid increase of population during the last century (18th). But the cheapness of this nourishing root, and the small piece of ground which, under this kind of cultivation, will in average years produce the food for a family, joined to the ignorance and depressed state of the people, which have prompted them to follow their inclinations with no other prospect than an immediate bare subsistence, have encouraged marriage to such a degree that the population is pushed much beyond the industry and present resources of the country; and the consequence naturally is, that the lower classes of people are in the most impoverished and miserable state.”