head. The inhabitants of the above city, struck with awe at so rare a phenomenon, vented their curses on the learned Marquis of Valle-Umbroso, who formed the hazardous resolution to attack their prejudices. I therefore left the persuasion they entertained, to make all the impressions which are usual in these cases; and endeavoured to explore the cause of the above-mentioned phenomenon, which I believe to be as follows.
"The spring was very rainy, and even on several days during the summer, a greater quantity of water fell on the coast than in the severest winter. It is natural to suppose that the abundant rain, combined with the great humidity of this valley, must have impregnated the earth with infinite vapours, which, being blended with so many other exhalations, would rise into the atmosphere, volatilized by the heat produced, as well by the perpendicular dire6tion of the solar rays in summer, as by the commotion of the central fire introduced by themselves into the present station. The heights there occupied by the aforementioned vapours must have been proportionate to their different specific gravity, by which they would equiliberate themselves with the columns of the aerial fluid. Thus some would rise to the upper part, while others would remain in the lower.
"The winds which, from the eastern quarter, are wont to blow gently at five in the evening, wandering and without any particular destination, having united them in such a way as that they appeared to be equally distant in every part at sunset, the imagination figured this arc. The tranquillity which prevailed, and the mutual attraction between some of the corpuscles and the others, kept them stationary, until the east wind, blowing with some degree of force, at the rising of the
