Letter to Sir Charles Lyell from Carlo Gemmellaro, principally replying to a letter sent to him by Lyell. He mentions the thickness and incline of lava flows of the Balzo of Aci Reale coming down from the side of Mount Etna, with sketch. He answers specific questions that Lyell has put to him in a previous letter regarding details of Gemmellaro's theory, stating that he does not feel himself obliged to accept the opinions of Waltershausen and mentions the discovery of some rocks at a beach near Mount Etna, which he feels goes against Waltershausen's theory, 01 May 1858.