The speaker imagines being something hard and lifeless, a stone, and the poem suggests this stone is grieving for what it used to be: a temple. A place built for reverence has collapsed into rubble, and the speaker seems to carry that loss. The second image is stranger and harsher. "A hanging jack to roast birds" points to a kitchen device that turns meat over a fire, so the speaker has gone from something sacred to something merely useful, even violent.
The last two lines step back and state the common thread: "that heat / could kill anything." Heat is the force running through the poem, and it feels total and indifferent. The mood is bleak and stripped down, with a quiet sense of grief rather than loud despair. The short lines and the lack of explanation leave the reader with a feeling of diminishment. Whatever the speaker once was has been worn down, transformed, or destroyed, and the poem simply lets that fact sit there, like a stone in the sun.