John Bates Clark,
Essentials of Economic Theory
“ They move labor from place to place in the system and they transfer capital to and fro in the same way. If we think of our table of groups and subgroups as representing the whole of this great industrial world, we must think of labor and capital as in a perpetual flow from subgroup to subgroup, making some industries larger and others smaller by reason of every such movement. The great force of labor and the fund of capital are like restless seas whose currents carry the water composing them now hither and now yon as the direction and force of the moving influences change. ”
