wichita.edu
…with continual feeding; which breaks out in a number of places. And strange it seemeth to a stranger, that men dare to walk up and down with so great a security: The Earth as hot, as sufferable, being hollow underneath; where the Fire and Water make a horrible rumbling, conjoining together, as if one were fuel to the other: here and there bubling up,…
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/volcanoes/chapter5.php