tended to cheapen bread as much as a very important discovery in agriculture would have done; and any great improvement in the construction of corn-mills, would have, in proportion, a similar influence. The effects of cheapening locomotion have been already considered. There are also engineering inventions which facilitate all great operations on the earth's surface. An improvement in the art of taking levels is of importance to draining, not to mention canal and railway making. The fens of Holland, and of some parts of England, are drained by pumps worked by the wind or by steam. Where canals of irrigation, or where tanks or embankments are necessary, mechanical skill is a great resource for cheapening production.
Those manufacturing improvements which cannot be made instrumental to facilitate, in any of its stages, the actual production of food, and therefore do not help to counteract or retard the diminution of the proportional return to labour from the soil, have, however, another effect, which is practically equivalent. What they do not prevent, they yet, in some degree, compensate for.
The materials of manufacture being all drawn from the land, and many of them from agriculture, which supplies in particular the entire material of clothing; the general law of production from the land, the law of diminishing return, must in the last resort be applicable to manufacturing as well as to agricultural history. As population increases, and the power of the land to yield increased produce is strained harder and harder, any additional supply of material, as well as of food, must be obtained by a more than proportionally increasing expenditure of labour. But the cost of the material forming generally a very small portion of the entire cost of the manufacture, the agricultural labour concerned in the production of manufactured goods is but a small fraction of the whole labour worked up in the commodity. All the rest of the labour tends constantly and strongly towards diminution, as the amount of production increases. Manufactures are vastly
