The Wealth of Nations by Part 2 Chapter 2 Page 21

his fixed and his circulating capital. While his whole capital remains the same, the smaller the one part, the greater must necessarily be the other. It is the circulating capital which furnishes the materials and wages of labour, and puts industry into motion. Every saving, therefore, in the expense of maintaining the fixed capital, which does not diminish the productive powers of labour, must increase the fund which puts industry into motion, and consequently the annual produce of land and labour, the real revenue of every society.

The substitution of paper in the room of gold and silver money, replaces a very expensive instrument of commerce with one much less costly, and sometimes equally convenient. Circulation comes to be carried on by a new wheel, which it costs less both to erect and to maintain than the old one.