Independently, however, of these causes, I think the frequent and sudden vicissitudes of temperature, which we suffer on the coast, are alone sufficient to account for the prevalence of catarrhal and pneumonic affections, which most commonly are the precursors of consumption. I trust the foregoing observations have not been considered too _medical_ to comport with the objects of this Society. Natural history is only useful in its practical applications; and if it can be shown to throw any light upon an art, which contributes so much to the comfort and happiness of man, we have established one of the strongest considerations, which can recommend it to general patronage and investigation. Physicians ought in an especial manner to set a high value upon the researches of naturalists. The aid they have already given is sufficient to entitle them to the lasting gratitude of our profession. It was one of the merits of that illustrious physician of our own time and country, Dr. Rush, that he seized with avidity every fact, from whatever quarter it might be drawn, to elucidate his favourite science. If ever medicine shall attain to the elevation of a truly _philosophical science_, it must be accomplished, in part at least, by imitating his example, and by developing the infinite and diversified associations which exist between it and the other sciences. ART. XIV. _Thoughts on Atmospheric Dust. By_ C. S. RAFINESQUE, _Esq._ 1. "When we find the ruins of ancient cities buried under ground; when the plough uncovers the front of palaces and the summit of old temples, we are astonished: but we seldom reflect why they are hidden in the earth. A sort of imperceptible dust falls at all times from the atmosphere, and it has covered them during ages." 2. These are the words of the worthy and eloquent philosopher VIREY, in his article Nature, Vol. XV. p. 373, of the French Dictionary of Natural History. Even before reading them I had observed the same phenomenon, and I have since studied their effects in various places. I could quote one thousand instances of the extensive and multifarious operations of this meteoric dust: but I mean to give the results merely of those that fall daily under notice, and are yet totally neglected; wishing to draw on them the attention of chemists, philosophers, and geologists. 3. Whenever the sun shines in a dark room, its beams display a crowd of lucid dusty molecules of various shapes, which were before invisible as the air in which they swim, but did exist nevertheless. These form the atmospheric dust; existing every where in the lower strata of our atmosphere. I have observed it on the top of the highest mountains, on Mount Etna, in Sicily, on the Alps, on the Alleghany and Catskill mountains in America, &c. and on the ocean.