Average Quantity of Ozone in the Atmosphere.—The quantity of ozone in the atmosphere is exceedingly minute. The proportion varies with the locality, the season, the hour, etc., as we have already seen, and it also varies with the altitude, for it is with this agent as with electricity—it increases as we rise above the earth. According to Houzeau, air of the country, about six feet above the earth, contains about 1⁄450000 of its weight of ozone, or 1⁄700000 of its volume. The quantity is so minute that it may probably be increased several fold without perceptible injury to man or animals.
Origin of Atmospheric Electricity and Ozone.—The sources of ozone in the atmosphere are almost innumerable. Like atmospheric electricity, it results from a wide variety of countless and ever-changing influences; it is one of the grand resultants of the ceaseless chemistry of the earth and sky. The evidence is now pretty clear that one prominent source of atmospheric ozone is in vegetable life. The oxygen that plants evolve from their leaves is more or less ozonized. It is claimed that ozone is developed with the perfume of flowers. The most odorous flowers, as the heliotrope, hyacinth, and mignonette, are the most prolific generators of ozone. This ozonic property of flowers is most manifest under the direct influence of sunlight. Lavender, fennel, mint, clove, and cherry-laurel, evolve ozone with special abundance when exposed to the solar rays. It is believed that the oxidation of essential oils, as anise-seed, bergamot, etc., under exposure to the light and air, develops ozone, and that in all flowers the source of the ozone is the essence; hence it is that the most odorous are the most ozoniferous.
If we accept these conclusions, we must also concede that the custom, now almost forgotten, among physicians, of providing the handles of their canes with vinaigrettes, with the fancy that the fumes would protect them against infectious disease, has a certain scientific basis. The aroma of snuff is said to develop ozone, and for years snuff has been regarded as a disinfectant.
Electricity, as is well understood, is generated by any kind of chemical change or action. Even friction and pressure cause electricity to be evolved, as was shown by Armstrong's experiments with jets of condensed air, liberated under high pressure. It was shown by Faraday that the friction of water dropping against bodies gives rise to electricity, and it is probable that the same effect follows the friction of water against air.
Volta showed, nearly a century ago, that the spray of a fountain furnishes negative electricity. Trolles, and afterward Humboldt, observed that a cascade or water-fall filled the air for some distance with negative electricity, and Bell thinks he has proved that a cascade is negative at the top, and positive at the bottom; that the positive electricity passes into the earth, leaving the negative in the spray.
We are then to look for the sources of ozone, as of electricity, in all
