What is the relation between the eternal law, the natural law and the human law?

[Jurisprudence] The eternal law, the natural law and the human law form a continuous series. The whole series may be compared to a tree, with the eternal law for its root, the natural law for its trunk, and the different system of human law for its branches. Wherever, the soil is not too bad and the climate favourable, the tree sends forth its splendid flowers of justice and equity and yields the fruits of peace and order, virtue and happiness.