There is now, certainly, no labour to be performed by water-carriers. But suppose that five hundred years ago, when there were a small number of persons who gained their living by such drudgery, they had determined to prevent the bringing of water by pipes into London. Suppose also that they had succeeded; and that up to the present day we had no pipes or other mechanical aids for supplying the water. It is quite evident that if this misfortune had happened--if the welfare of the many had been retarded (for it never could have been finally stopped) by the ignorance of the few--London, as we have already shown, would not have had a twentieth part of its present population; and the population of every other town, depending as population does upon the increase of _profitable_ labour, could never have gone forward. How then would the case have stood as to the amount of labour engaged in the supply of water? A few hundred, at the utmost a few thousand, carriers of water would have been employed throughout the kingdom; while the smelters and founders of iron of which water-pipes are made, the labourers who lay down these pipes, the founders of lead who make the service-pipes, and the plumbers who apply them; the carriers, whether by water or land, who are engaged in bringing them to the towns, the manufacturers of the engines which raise the water, the builders of the houses in which the engines stand--these, and many other labourers and mechanics who directly and indirectly contribute to the same public advantage, could never have been called into employment. To have continued to use the power of the water-carriers would have rendered the commodity two hundred times dearer than it is supplied by mechanical power. The present cheapness of production, by mechanical power, supplies employment to an infinitely greater number of persons than could have been required by a perseverance in the rude and wasteful system which belonged to former ages of ignorance and wretchedness. When a severe frost chokes up the small water-pipes that conduct the useful stream into each house, what anxiety and trouble is there in every thoroughfare! The main pipes are not frozen; and the supply is to be got in pails and pitchers from a plug in the pavement, where a temporary cock is inserted. How gladly is this device resorted to! But imagine it to be the labour of every day, and what an amount of profitable time would be deducted from domestic employ! [Illustration: Plug in a frost.]