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…Campagna di Roma, which is full of sulphurous Crater’s. through the Minturnan Marshes to Sumo: whence a continued Mine of Sulphur, through the Roman Plain exerts itself, in divers places, but chiefly, in a certain Lake of unsearchable profundity, four miles distant from the City Tivoli, as also the most famous of the sixteen swimming Islands thereabouts,…
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/volcanoes/chapter3.php