liberty of asking if you have any idea as to the cause of the large quantity of carbonic acid which you have been so good as to inform us exists in most of the waters in this country?” The stranger replied, “I certainly have formed an opinion on this subject, which I willingly state to you.  It can, I think, be scarcely doubted that there is a source of volcanic fire at no great distance from the surface in the whole of southern Italy; and, this fire acting upon the calcareous rocks of which the Apennines are composed, must constantly detach from them carbonic acid, which rising to the sources of the springs, deposited from the waters of the atmosphere, must give them their impregnation and enable them to dissolve calcareous matter.  I need not dwell upon Etna, Vesuvius, or the Lipari Islands to prove that volcanic fires are still in existence; and there can be no doubt that in earlier periods almost the whole of Italy was ravaged by them; oven Rome itself, the eternal city, rests upon the craters of extinct volcanoes; and I imagine that the traditional and fabulous record of the destruction made by the conflagration of Phaeton in the chariot of the sun and his falling into the Po had reference to a great and tremendous igneous volcanic eruption, which extended over Italy and ceased only near the Po at the foot of the Alps.  Be this as it may, the sources of carbonic acid are numerous, not merely in the Neapolitan, but likewise in the Roman and Tuscan states.  The most magnificent waterfall in Europe, that of the Velino, near Terni, is partly fed by a stream containing calcareous matter dissolved by carbonic acid, and it deposits marble, which crystallises even in the midst of its thundering descent and foam in the bed in which it falls.  The Anio or Teverone, which almost approaches in beauty to the Velino in the number and variety of its falls and cascatelle, is likewise a calcareous water; and there is still a more remarkable one which empties itself into this river below Tivoli, and which you have probably seen in your excursions in the campagna of Rome, called the lacus Albula or the lake of the Solfatara.”  Ambrosio said, “We remember it well, we saw it this very spring; we were carried there to examine some ancient Roman baths, and we were struck by the blue milkiness of the water, by the magnitude of the source, and by the disagreeable smell of sulphuretted hydrogen which everywhere surrounded the lake.”  The stranger said, “When you return to Latium I advise you to pay another visit to a spot which is interesting from a number of causes, some of which I will take the liberty of mentioning to you.  You have only seen one lake, that where the ancient Romans erected their baths, but there is another a few yards above it, surrounded by very high rushes, and almost hidden by them from the sight.  This lake sends down a considerable stream of tepid water to the larger lake, but this water is less strongly impregnated with carbonic acid; the largest lake is