the raw products of the soil, in an advancing community, steadily tend to rise in price. Now, the most elementary truths of political economy show that this could not happen, unless the cost of production, measured in labour, of those products, tended to rise. If the application of additional labour to the land was, as a general rule, attended with an increase in the proportional return, the price of produce, instead of rising, must necessarily fall as society advances, unless the cost of production of gold and silver fell still more: a case so rare, that there are only two periods in all history when it is known to have taken place; the one, that which followed the opening of the Mexican and Peruvian mines; the other, that in which we now live. At all known periods, except these two, the cost of production of the precious metals has been either stationary or rising. If, therefore, it be true that the tendency of agricultural produce is to rise in money price as wealth and population increase, there needs no other evidence that the labour required for raising it from the soil tends to augment when a greater quantity is demanded.
I do not go so far as Mr. Carey: I do not assert that the cost of production, and consequently the price, of agricultural produce, always and necessarily rises as population increases. It tends to do so; but the tendency may be, and sometimes is, even during long periods, held in check. The effect does not depend on a single principle, but on two antagonizing principles. There is another agency, in habitual antagonism to the law of diminishing return from land; and to the consideration of this we shall now proceed. It is no other than the progress of civilization. I use this general and somewhat vague expression, because the things to be included are so various, that hardly any term of a more restricted signification would comprehend them all.
Of these, the most obvious is the progress of agricultural knowledge, skill, and invention. Improved processes of agriculture are of two kinds: some enable the land to yield a greater absolute produce, without an equivalent increase of
