only could decompose the neutral potassium iodide; but Andrews demonstrated that the body in the atmosphere that did this is identical with Ozone. Dr. C. B. Fox, of the Royal College of Physicians, London, repeated the various experiments of his predecessors, and declares the matter placed beyond a doubt. Observation shows that Ozone is more abundant at a distance than near the earth's surface. Seaside places are visited by a greater quantity when the winds blow from the sea, than when they proceed from the land; the sea being a great manufactory of allotropic oxygen. There is usually a greater development in February and May than in other months; autumn having the least. A large fall of rain is characterised by the increase; and the amount has been thought to be greater when we have a new or full moon than during the first and third quarters. In eclipses the amount is often very large, but in earthquakes the reverse is the case. In short, Ozone is contained in the air in larger quantity in winter and spring than during the summer and autumnal months. The frequent storms and maximum of electricity with low temperature and activity of vegetation in spring, are doubtless the occasion of this larger amount; while the higher temperature, the decomposition of animal and vegetable matter, and the minimum of electricity in the lower strata of the atmosphere are causes of its diminution at other periods of the year.

"Ozone is found in greater abundance," says Dr. Fox, “in pure country-air than in impure town-air, on mountains than in valleys, at the seaside than inland, in well-drained and ventilated towns than in those where these important sanitary matters are neglected." It is the great deodorising and purifying principle of nature, and therefore is consumed in the oxidation of the noxious exhalations, where human beings are closely aggregated together. Here Dr. Shapter could find little in the city of Exeter, in England, and Dr. Angus Smith could find none in the air of Manchester. Dr. C. Evans observed that the northeast wind which reached Hackney from the country was highly charged with Ozone, but on arriving at Fulham, after having crossed London, had lost nearly all traces of this substance. On the other hand, the southwest

wind arriving at Fulham was rich with it, but on reaching Hackney, after passing London, was almost destitute of it. Lyons, in France, has been named "the town without Ozone." At Geneva and Chamouni the quantity is very large. Dr. Wetherill ascertained that the air of the public grounds at Washington yielded an abundance of Ozone at night, while that of the streets of the city, at the same time, indicated an absence of this gas. At seaside stations there is an enormous

amount.

The municipal body of Paris organised a series of daily observations in 1866 and 1867, in the various arrondissements of that city, with most significant results. I extract the following as most instructive :

At Passy, near resinous trees, the mean was 6.39; at La Villette, close to a quay on the Seine, 0.96; at Menilmontant, near a tallow manufactory, 1.16; at Fountaine-Moliere, almost directly over a public urinal, 0.38; at the Ecole de Medicine, close to an hospital, 0.80; at Rue Racine, near a reservoir, 1.69; at the Reservoir de Vaugirard, 8.37; at La Chapelle, close to Artesian wells, 3.08, and at Butte-aux-Cailles also near such wells, 4.79.

Professor Heaton and others declare that Ozone is always absent from the air of an inhabited room, even though the window is open. This, however, is disputed. It has also been declared by the best continental authorities to be almost entirely absent from the air of hospitals, especially of those devoted to fever patients. Means for its artificial generation have been accordingly suggested.

The preponderance of Ozone in sea-winds has been noted in various parts of the world. Admiral Fitzroy lays down the rule in the Weather-Book that the winds which accompany the greatest indications of Ozone are those which blow from the nearest and largest sea. Tests were said to read about one-third higher when sea-winds blow than during the prevalence of land-winds.

M. Morin explains that the pulverising of water, as into the form of spray, is always accompanied by the development of Ozone. This change in the condition of the air, it will be remembered, is largely produced by passing the electric current

through it. That electricity is developed in sensible quantities in the neighborhood of waterfalls, and in large amount on the sea-shore, particularly when the waves dash themselves violently against the rocks creating much spray, is well known. Sea-water also holds in solution about one-thirtieth of its volume of air. It has been shown that this air contains 32 per cent. of oxygen, whereas the air over land has only 21 per

cent.

Plants evolve Ozone from their leaves and green parts, and set more free during the daytime than can be found in the air about them. The same thing is also true during the night when they grow thickly and vigorously, but not in the case of isolated vegetation. Plants growing in the country give off more Oxone during the day than town-plants. In the midst of towns and a dense population, night-air exhibits a larger proportion than day-air; but as the animal population diminishes and the vegetable kingdom predominates, the daily supply is increased till it exceeds that of the night. The interiors of the corollas of plants do not produce it.

Dr. Danberry, following up these experiments, concluded that atmospheric Ozone was due almost entirely to plants, being generated by the green parts during the day while emitting oxygen; the flowers producing none.

PERFUME OF PLANTS A GENERATOR OF OZONE.

The disciples of the philosopher Empedokles planted aromatic and balsamic herbs as prophylactics against pestilence. The researches of modern observers appear to justify their notion. Lawes, Gilbert and Pugh have attributed the production of Ozone in vegetation rather to the intense effect of the atmospheric oxygen upon the minute quantities of volatile hydrocarbons evolved by the plants, than to any action within the cells. Montegazza states that odoriferous flowers discharge a large quantity, but flowers without perfume are destitute of it. Cherry-laurel, clover, lavender, mint, lemon, fennel, develop it largely in the sunshine; so do the flowers of heliotrope, narcissus, hyacinth and mignonette, as well as the essential oils, such as nutmeg, aniseed, thyme, pepper

mint, etc. Ancient physicians regarded the odor of laurel as a disinfectant. They seem to have been correct. The sunflower is also said to exhale Ozone in large quantities; and Dr. J. Murray even attributed this virtue to the aroma of powdered tobacco.

OZONE FROM ATMOSPHERIC ELECTRICITY.

Faraday has shown that the friction of water-drops against all bodies develops in them a most powerful charge of negative electricity. Doubtless the contact with the air has the like influence. Volta found it to be produced by allowing the fine spray of a fountain to fall on the plate of a straw electroscope. Humboldt observed that the spray of a waterfall or a lofty cascade filled the air of the neighborhood with negative electricity, which can be detected at three or four hundred feet distant. As electric discharges are incessantly taking place the production of Ozone is therefore constantly maintained,

Saint Pierre ascertained that Ozone was developed by the mechanical action of blowing machines and ventilators producing strong currents. This fact, he suggests, may account for the healthy action of winds. Perhaps the attrition of the particles of air against each other has the same effect. Storms, tempests, hurricanes and water-spouts are all active in this way, and so beneficial.

OZONE IN EPIDEMIC.

Different opinions have been given in regard to the influence of atmospheric Ozone upon the public health. Dr. Tripe declared that during the seven weeks of the last quarter of the year 1857, no Ozone was present at Hackney, and that notwithstanding there was no disease prevalent during that period, and the mortality was below the average; while London had five per cent. in excess at the same time. Other writers have also conjectured that cholera years were characterised by an excess.

More extensive observations, however, seem to have utterly dissipated these opinions. The members of the Scottish Meteorological Society carried out a series of observations in one

of the suburbs of Edinburgh, and perceived that when the largest quantities of Ozone were obtained "the air had a pleasant sharpness to the feelings, exercising, as it were, a stimulating influence on the spirits. When on the other hand, the air was close and seemed to exert a slightly-depressing effect, little if any Ozone was detected." Schonbein declared his belief that a deficiency of Ozone or an excessive production of miasmatic matters in the atmosphere, favors the propagation of epidemic diseases; mentioning in corroboration that Ozone is most abundant in winter when zymotic diseases are least plentiful. It would be necessary, however, to show whether it affects the poisons which generate them. We know that it will destroy noxious odors; but can putrescent emanations produce a disease? The earlier comparisons between the prevalence of cholera and the presence of Ozone in the atmosphere, appear to have exhibited contradictory results. The outbreak generally took place when the quantity of Ozone approximated a minimum, but its increase did not seem to have a decided influence in the way of arresting the progress of the visitation. In catarrhal and pulmonary disorders, atmospheric Ozone appears to be of little benefit in advanced stages, but highly beneficial at first. Catarrh and influenza are seldom experienced in an atmosphere highly ozonised. Tubercle will be removed by the constant contact of air in this condition. Rheumatism is also radically cured.

MALARIA.

The Rev. Henry Ward Beecher declares that malaria is like a heavy wet blanket thrown over the medical profession. It is certainly a convenient term to use, when something must be said to show people that the physician knows something, and the rationality of it is not in question. True, nevertheless, that no malarious air has ever disclosed other elements than the common atmosphere. The chilly evenings succeeding to sultry debilitating days check the insensible perspiration, leaving the body loaded with its own poison, which is worse than any thing often found in the external air. The Roman Campagna can be safely visited by any body properly dressed.