Where is this from, what's it mean, and what do you think about it?

Question:

Where is this from, what's it mean, and what do you think about it?

"I am the daughter of Earth and Water,
And the nursling of the sky;
I pass through pores of the oceans and shores;
I change, but I cannot die."

Best Answer - Chosen by Asker:

This is an extract of The Cloud, by Percy Shelley. It was first published in 1820, and the passage you've got is the beginning of the last stanza.

The poem is full of scientific knowledge (hydrological speculations, cloud classification -- quite new at the time), and in the bit that interests you, Shelley's central preoccupation is less with the varying physical manifestations of clouds and more with the animating energy or spirit, which operates invisibly behind each shifting cloud-formation that it adopts. Shelley is intrigued by the cloud's delicately negotiated mode of being between corporeal and spiritual states, in which he finds a symbol for both the workings of the mind and the quest of the human soul.

The lyric's meditation on the metaphysical status of the cloud's spirit is infused by Shelley's knowledge of contemporary science; his imagery of the ??pores of the ocean and the shores?? is derived from hydrological theories by his contemporaries. The dissipation of the cloud's physical presence is not confirmation of a final demise, but an affirmation of the continued existence of its vital, unseen, animating spirit.
In the spirit's capacity to resurrect itself, Shelley finds a reminder of our own limited mortality. I understand it as a hopeful analogy to assert the continued existence of our spirits or minds after our bodies cease to exist.