Note 23 — LETTER IV.
Reading edition
This passage, in Cornelius Severus's poem upon Etna, seems to confirm my opinion:
"Placantesque etiam cælestia numina thure "Summo cerne jugo, vel quâ liberrimus Ætna "Improspectus hiat; tantarum semina rerum "Si nihil irritet flammas, stupeatque profundum."