Sentence:  ... beneath him sound like waves on a desert shore / The voice of slaves beneath the sun, and children bought with money, / That shiver in religious caves beneath the burning fires / Of lust, that <WSD>belch</WSD> incessant from the summits of the earth. 
Meaning of the word marked with <WSD> tags:  To be ejected or emitted ("from" something) with spasmodic force or noise.