Join with all nature in manifold witness

In the song Great is Thy faithfulness there is a line that reads

Join with all nature in manifold witness

What does that mean? What is manifold witness?


"Manifold" has the meaning of :

having many different forms, features, or elements:

The fact that the "sun, moon, and stars", are joining the whole of nature as a witness(like in a court)of God's great faithfulness, mercy, and love. Because it is the "whole of nature", this witness is bound to be composed of "many different elements".