Seneca was prepared to believe that great changes had been wrought by earthquakes on the face of the land. He cites in support of this view some remarkable examples which had occurred within the times of human history, such as the sinking of the towns of Buris and Helice, the disappearance wholly or partially of the island of Atalanta, and the subsidence of Sidon (256). He refers also to various striking features of landscape in different regions which had been popularly assigned to the work of earthquakes, such as the separation of Ossa and Olympus, the disruption of Sicily from the Italian shore, and the severance of Spain from the continent of Africa (263). That the phenomena of earthquakes are closely connected with those of volcanoes was the general belief in antiquity, and continued to be accepted up to the middle of last century. It was believed in early days that just as the collision of clouds during storms produces the fire seen in lightning, so during the tempestuous agitation of the air within the earth, such heat is generated as to set fire to beds of sulphur or other combustible materials, and thus that rocks are melted and are forced up to the surface by the vast energy of the escaping air.[121] It is to be regretted that Seneca has not left an account of his own opinions on this subject, but from the allusions in the present treatise he may be inferred to have held the prevalent opinion. He alludes in various passages to volcanic eruptions that had taken place in his own time, or not long before, in the Mediterranean basin. An eruption of Etna is briefly noticed, when the mountain was in violent eruption, ejecting such a quantity of fine burning sand and dust as to turn day into night, accompanied with much thunder and lightning (77). This may have been the eruption alluded to in similar language by Cicero, who adds that for two days nobody could see his neighbour.[122] Seneca further cites two eruptions in the Aegean Sea, one of which had taken place in his own time, when a new island was upraised “by the force of air.” He alludes to Thera and Therasia, and the interesting account given by Posidonius of the uprise of an island in the same sea, with attendant circumstances closely resembling those of the eruptions at Santorin in modern times (73, 252). According to Asclepiodotus, the fire, after overcoming the resistance of the thick mass of sea, shot up above sea-level to a height of two hundred paces. [121] This view of the nature of volcanic energy is graphically expressed by Lucretius (_op. cit._ vi. 639–702). [122] _De Nat. Deor._ ii. 38. See also Lucretius (_ib._ vi. 641), who describes the more conspicuous features of an eruption, and concludes with the line ne dubites quin haec animai turbida sit vis (693).