What is the meaning of the simile " a bright girdle" in this excerpt from "dover beach" by matthew arnold

The user the did not post the excerpt. The excerpt is given below:
The Sea of Faith
Was once, too, at the full, and round earth's shore
Lay like the folds of a bright girdle furled.
But now I only hear
Its melancholy, long, withdrawing roar,
Retreating, to the breath.

The simile 'a bright girdle' as used in this excerpt SUGGESTS THE GREATNESS OF AN ERA WHEN ENGLAND WAS A WORLD POWER AND COMMERCIAL SUCCESS.
The poem 'Dover Beach is the best known poem of Mathew Arnold, he wrote the poem in 1851 during his visit to the south coast of England, where the cliffs of Dover was located.