far as my experience, a very limited one, however, has gone, it is effectual. I ventured to ask him what the bottle might contain, as such a benefit ought to be made known to the world. He replied, "It is a mixture which slowly produces the substance called by chemists chlorine, which is well known to be generally destructive to contagious matters; and a friend of mine who has lived for many years in Italy, and who has made a number of experiments with it, by exposing himself to the danger of fever in the worst seasons and in the worst places, believes that it is a secure preventive. I am not convinced of this; but it can do no harm; and in waiting for more evidence of its utility, I employ it without putting the least confidence in its power; nor do I expose myself to the same danger as my friend has done for the sake of an experiment." I said, "I believe several scientific persons--Brocchi amongst others--have doubted the existence of any specific matter in the atmosphere producing intermittent fevers in marshy countries and hot climates; and have been more disposed to attribute the disease to physical causes, dependent upon the great differences of temperature between day and night and to the refrigerating effects of the dense fogs common in such situations in the evening and morning; and, on this hypothesis, they have recommended warm woollen clothing and fires at night as the best preventives against these destructive diseases, so fatal to the peasants who remain in the summer and autumn in the neighbourhood of the maremme of Rome, Tuscany, or Naples." The stranger said, "I am acquainted with the opinions of the gentlemen, and they undoubtedly have weight; but that a specific matter of contagion has not been detected by chemical means in the atmosphere of marshes does not prove its non-existence. We know so little of those agents that affect the human constitution, that it is of no use to reason on this subject. There can be no doubt that the line of malaria above the Pontine marshes is marked by a dense fog morning and evening, and most of the old Roman towns were placed upon eminences out of the reach of this fog. I have myself experienced a peculiar effect upon the organs of smell in the neighbourhood of marshes in the evening after a very hot day; and the instances in which people have been seized with intermittents by a single exposure in a place infested by malaria in the season of fevers gives, I think, a strong support to something like a poisonous material existing in the atmosphere in such spots; but I merely offer doubts. I hope the progress of physiology and of chemistry will at no very distant time solve this important problem." Ambrosio now came forward, and bowing to the stranger, said he took the liberty, as he saw from his familiarity with the cicerone that he was well acquainted with Paestum, of asking him whether the masses of travertine, of which the Cyclopean walls and the