Letter to Sir Charles Lyell from Carlo Gemmellaro replying to earlier letters from Lyell to the Gemmellaro family containing questions relating to the geology of Mount Etna. Gemmellaro diagrees with Lyell that the pressure of subsequent layers of lava depress those beneath, with sketch, and mentions the geographical locations of certain features with respect to the map of Wolfgang Sartorius Von Waltershausen which Gemmellaro feels to be accurate, 21 May 1858.