It is, however, also to be considered, on the other side, that the French army was more exposed to the epidemic influence of the air, the water, and the general powers of nature, than any other assemblage of men, and, that this influence was probably more powerful in the year 1529, than at any other time during the sixteenth century. The formation of fog in the heat of summer is at all times an extraordinary phenomenon[512], which decidedly indicates a disproportion in the mutual action of the components and powers of the lower strata of the atmosphere. This was not dependent merely on the local peculiarities of Naples, for during the summer of 1528, grey fogs were observed throughout Italy, which rendered the unwholesome quality of the air visible to the eye[513]. This was increased by the prevalence of southerly winds, which are always, in Italy, prejudicial to health, as also by the thousand privations of a camp, so that a disease which was already prevalent all over Italy,—we allude to the _petechial fever_,—might well break out on the damp soil of Poggio reale. In the history of national diseases, we find a moral proof of the predominance of epidemic influence which plainly and intelligibly manifests itself under the greatest variety of circumstances. This is a belief, that the water, and even the air is poisoned[514]. Nor is this proof wanting in the deplorable history of the French army before Naples, for it was generally believed, that some Spaniards of Moorish descent, to whom was attributed an especial degree of skill in the management of poison, and some Jews from Germany, who, for the sake of gain, had followed the lansquenets to truckle for their booty, had stolen out of the city under cover of the night, in order to poison the water in the neighbourhood of the camp[515]. It was also surmised, that an Italian apothecary had administered to the French knights poison in their medicine[516]. We will not anticipate on this occasion the researches of naturalists, whose experiments on air and water, during important epidemics, have not yet led to any results; it is, however, not improbable that pond and spring water, under such circumstances as are here described to have occurred, might become impregnated with a noxious quality not inherent in it, which would very naturally give rise to the belief that a poison had been thrown into it. On the whole, this accusation may certainly be judged according to the same views which have been stated in our treatise on the Black Death.