AGNANO, LAGO D', a small circular lake, near Naples, about two miles in circumference, and evidently the crater of a volcano, now filled with water. On its banks are the stufe, or natural vapour-baths of San Germano, and on its opposite shore is the famous Grotta del Cane, from the floor of which carbonic acid is continually evolved, in such quan-
tivity as to kill dogs that enter it, while a man, on account of his erect posture, escapes wholly the effect of the gas. (See Spallanzani's Travels.) This grotto is a small artificial excavation 12 feet long by 4 or 5 wide, and 6 feet high, seemingly made for obtaining puzzolano, or earthy volcanic tufa. The story of birds not frequenting the lake is erroneous, for it abounds in teal ducks and other birds, and in frogs.