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…her self with underground; in her inward parts, for the necessary uses and occasions of her exterior, &c. As was at the beginning observ’d. The reason of this flame is thus set down by Ovid. A Rozen Mould these fiery flames begin,And Clayze Brinstone aids that Fire within:Yet when the slimy Soyl, consumed, shallYeeld no more food to feed the Fire…
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/volcanoes/chapter6.php