This hymn text by Eliza R. Snow touches on a rather unusual doctrine, which she must have learned at the feet of the Prophet: the concept that from time to time, pieces of the Earth have been flung off into space, only to be regathered in the Millenium.
Astronomers are in general agreement that the Moon was formed about 4.5 billion years ago from a catastrophic collision between the Earth and some Mars-sized planet. Perhaps some day we will understand the full import of what Sister Eliza was alluding to in this strange hymn.
The full text was published in the Times and Seasons, as recorded here: http://www.losthymnsproject.com/14_Texts/Thou-Earth-Wast-Once-a-Glorious-Sphere.pdf
PDF: Thou Earth wast once