“Its circular form, and being in the centre of a volcanic district, hashed to its being regarded as an extinct crater; but that hypothesis can scarcely be admitted when the great extent of the lake is considered. The treacherous beauty of the lake conceals malaria in its most fatal forms; and its shores, although there are no traces of a marsh, are deserted, excepting where a few sickly hamlets are scattered on their western slopes. The ground is cultivated in many parts down to the water’s edge, but the laborers dare not sleep for a single night during the summer or autumn on the plains where they work by day; and a large tract of beautiful and productive country is reduced to a perfect solitude by this invisible calamity. Nothing can be more striking than the appearance of the lake, without a single sail upon its waters, and with scarcely a human habitation within sight of Bolsena; and nothing perhaps can give the traveller who visits Italy for the first time a more impressive idea of the effects of malaria.”