The theory of interest was wrapped in utter obscurity, until Hume and Smith dispelled the vapor. - Jean-Baptiste Say

An uniformity of weights and measures, arranged upon mathematical principles, would be a benefit to the whole commercial world, if it were wise enough to adopt such an expedient.

Labour, upon whichever of those operations it be bestowed, is productive, because it concurs in the creation of a product. Thus the labour of the philosopher, whether experimental or literary, is productive; the labour of the adventurer or master-manufacturer is productive, although he perform no actual manual work; the labour of every operative workman is productive, from the common day-labourer in agriculture, to the pilot that governs the motion of a ship.

capital cannot be more beneficially employed, then in strengthening and aiding the productive powers of nature.