Sir Charles Lyell derives an argument against the theory of central heat, from the consideration that it would, in his opinion, involve the existence of tides in the internal fire-ocean, which tides would register themselves in the swellings and subsidences of volcanoes. 'May we not ask,' he says, 'whether, in every volcano during an eruption, the lava which is supposed to communicate with a great central ocean, would not rise and fall sensibly; or whether, in a crater like Stromboli, where there is always melted matter in a state of ebullition, the ebbing and flowing of the liquid would not be constant?' We venture to remark that this argument does not seem unanswerable. No one denies that the crust is at present consolidated to the depth of at least from thirty to eighty miles. The capacity of known chemical forces to produce intense heat in this region is not disputed. The eruptions of now active volcanoes might arise, therefore, from processes going on in a part of the crust separated by solidified strata from the internal reservoir of liquid fire, and not accessible to its tides. We might ask also, in turn, whether observations have been made upon volcanoes in a state of eruption, exact enough to determine whether they are or are not influenced by internal tides? It is affirmed by Mr. David Forbes, in a recent number of _Nature_, that Professor Palmieri stated, as the result of observations made by him during the last eruption of Vesuvius, 'that the moon's attraction occasioned tides in the central zone of molten lava, in quite a similar manner as it causes them in the ocean.' Mr. Forbes adds that 'a further corroboration of this view is seen in the results of an examination of the records of some 7,000 earthquake shocks which occurred during the first half of this century, compiled by Perry, and which, according to him, demonstrate that earthquakes are much more frequent in the conjunction and opposition of the moon than at other times, more so when the moon is near the earth than when it is distant, and also more frequent in the hour of its passage through the meridian.' If these statements are correct--and we have no reason to call them in question--the supposed fact, which Sir Charles presumed to tell in his favour, has been converted into an ascertained fact which tells most forcibly against him. In the latest edition of his 'Principles of Geology,' Sir Charles Lyell seems, in at least one passage, to assume that this controversy is at an end.