Definition of "undeclining"

In vain! In vain! wild storms will rise and o'er your fabrics sweep,Yet when loud thunders wake the wave, and deep replies to deep,When in your path, Hope's broken prism doth shed its parting ray,Spring up and fix your tearful eye on undeclining day.

1842, Lydia Sigourney, Poems, "This is not your rest.", page 79