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…of Putzol, or Puteoli, near Naples, by Athanas. Kircher, his own Observation, An. 1638. In the Year 1638, passing by Naples, I could not let slip the opportunity of inquiring and looking into these sulphureous Plains, so much celebrated in all Ages: Which the Antients called the Phlegraean Plains. Having therefore got through a subterraneous passage, which…
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/volcanoes/chapter5.php