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were usually accompanied by an increase of positive electricity; this observation is of interest, because it accords with the fact that the approach of snow-storms and the presence of simple fog do not cause the exacerbations of rheumatic and neuralgic pains that are experienced on the approach of storms of rain, or thunder and lightning.

Ozone-History.—From the earliest recorded ages a peculiar odor has been observed during thunder-storms and other electrical disturbances, and especially in connection with flashes of lightning. The peculiar odor of thunder-bolts has been referred to by Homer, both in the "Iliad" and the "Odyssey." Jupiter is said to strike a ship with a thunder-bolt, "ὲν δὲ νέειον πὰῆτο" full of sulphurous odor, and to hurl a bolt into the ground "with the flame of burning sulphur." This peculiar sulphurous odor has been observed not only during thunder-storms, but also, it is said, during displays of northern and southern auroræ.

So long ago as 1785, Van Marum, of Holland, observed that electric sparks passed through oxygen gas (that had been discovered by Priestley only eleven years before) gave rise to a peculiar sulphurous or electrical odor; and, at the beginning of the present century, Cavallo, a prominent name in the history of electricity, called attention to the fact that this "electrified air," as it was termed, had an antiseptic effect on decomposing matter, and was a salutary application for fetid ulcers. In 1826 Dr. John Davy, in a measure anticipating Schönbein, recognized this peculiarity of the atmosphere, and devised tests for detecting it.

The real scientific history of ozone dates from 1839, when Prof. Schönbein, of Basle, the renowned inventor of gun-cotton, observed that the electrolytic decomposition of water was attended by a peculiar odor resembling that evolved during the working of a fractional electric machine. In 1840 Schönbein called the attention of the scientific world to the newly-discovered substance, to which he gave the name of ozone, from the Greek ὅἕω, to emit an odor. He showed that this odor appeared at the positive pole during the electrolysis of water. He furthermore pointed out that ozone may be produced by the slow oxidation of phosphorus in moist air or oxygen, and that the odor was similar to that which is observed during flashes of lightning. Schönbein studied hard on the subject for many years, and arrived at the conclusion that oxygen is capable of division into a negatively polar state, ozone, and a positively polar state, which he called antozone. During the past quarter of a century the subject of ozone has been studied by some of the most eminent scientists of the age, among whom we may mention the names of Berzelius, De la Rive, Marignac, Becquerel, Faraday, Fremy, Meissner, Houzeau, Scoutteten, Odling, Andrews, Tait, Fox, Fischer, Boeckel, Zeuger, Moffat, Nasse, Engler, Erdmann, Angus Smith, Poey, A. Mitchell, Soret, Baumert, Williamson, and very many others.