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…of which, the sulphureous River of Tyber has its origine; and seems to have been famous heretofore, for hot Bath’s. Hence a burrow of subterraneous fire, bends back to the Round Mountain; And thence into divers branches. One part whereof tends to the Stiglian Bath’s, and the Lake in the middle Wood, horrible with stench of Brimstone, and for the spectacle …
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/volcanoes/chapter3.php