In the year 1783 all Europe and a portion of Asia were enveloped in a dense fog of a most remarkable nature. It was termed “dry,” as even at night no dampness was observed. It was first seen at Copenhagen, its coming being heralded by severe storms. A few weeks later it appeared in various parts of France, and rapidly seemed to spread over Europe and portions of Asia. During the day it had a metallic glow, which at night changed to a phosphorescent light, so brilliant that ordinary print could be read by it. Many attempts to explain it were made by the savants of the day, and it was universally supposed to be due to the earthquakes and volcanic eruptions which were of unusual severity that year. A somewhat similar fog appeared in the United States, a portion of Europe, and Africa in August, 1831. The daylight was perceptibly diminished, while at night a conspicuous phosphorescent light was emitted. A remarkable luminous fog occurred in Switzerland in 1859. M. L. F. Wartmann of Geneva states that the strange light was observed on five successive nights, and apparently proceeded from a heavy dry fog that hung over Geneva during the time. The light was so brilliant that this gentleman distinguished the smallest objects upon his table with perfect ease, no other light being in the apartment. The light caused general comment in the places in which it appeared, and a traveller between Geneva and Annemassi stated that he readily found the road by its means. Dr. Verdeil of Lausanne describes a fog which diffused so much light that distant objects were perfectly visible at night. Among the phenomena which attended the eruption of Vesuvius in 1794 was one which did not tend to allay the fears of the people. During the day a fine dust filled the air about Naples, which was not particularly noticeable; but as night came on, it emitted a pale though distinct phosphorescent light. An English gentleman sailing near Torre del Greco noticed that where the dust collected upon his hat it was luminous, and no little consternation was caused among the superstitious sailors by the occurrence. Luminous dust-showers have been noticed in several localities; and the peculiar glows that were seen in this country a few years ago were accredited by many to them, the supposition being that dust, perhaps from volcanic eruptions, was floating about in the upper strata of the atmosphere. Many other explanations were given, and the literature upon the subject is extremely voluminous and interesting. The amount of material floating about in the upper regions of the air is perhaps little realized by my young readers, and some reference to the phenomenon may be of interest.