Licence: Public Domain Mark
Credit: The atmosphere in relation to human life and health. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![day's iJiiii on the low ^loiiiul, prove how eoiiiuionly iiiiii is melted iee or snow. Other solid partieles always present in f^reat ii inn hers in 1 he lower air, andotj;reat iinportaiiee in relation to human, animal, and plant life, are various kin<ls of microbes, l'unp;i, molds, and spores. At certain sea- sons the ])ollen oC plants is \ei-y abundant. In some countries the air is thick in (he diy and windy season with tlie dust of tlie soil. Agri- cultural lires cause a thick haze over parts of Germany, the United States, ;iud other countries at certain times of the year. After great volcanic eruptions the air over many thousand stjuare miles has been ailected by a dense haze. This was notably the case in the summer of 1783, when, after an eruption in Iceland, terrestrial and celestial objects were dimmed by dry fog in western and central Europe dur- ing several weeks. In 18S;5, on the other hand, after the eruption of Krakatoa, near Java, the upper air, between 40,000 and 120,000 feet in altitude, was overspread with a semitransparent hazeof a very remark- able character, consisting nminly of linely divided, glassy pumice. This haze stratum in the upper sky extended over all known countries and remained visible for several months. Cloud globules are the most obvious and widely present liquid ingre- duMits of the atmosphere. They possess properties of great interest in connection with the recently discovered ubiquitous atmospheric dust, with optical phenomena, and with the formation and distribution of rain. The other familiar forms of water in the air are dry and damp fogs, mist, and rain. Haze is in most instances, at least so far as the pres- ent writer's observations go, in the south of England, a phenomenon depending on very small particles of water and on the presence of dust particles as nuclei. Ozone, an allotropic and unstable form of oxygen, has been found to be constantly presenl, in very small quantities, in the ojren air in nat- ural conditions, but can not be traced in the impure air of great towns, and is no doubt always greatly diminished where dwellings are thick together. Ozone consists of molecules, each supposed to contain three molecules of oxygen. Peroxide of hydrogen is also supposed to exist in slight traces in the general atmosphere. Minor impurities, arising from animal life, from manufacturing I^rocesses, and from the combustion of coal, are mostly not perceptible to the senses, except in the neighborhood of places where they are given oil very abundantly. The principal functions of all these various elements and substances of which the atmosphere is composed, may now be regarded in detail with special reference to their influence upon human life and welfare. OXYGEN. Oxygen, that wonderful element which constitutes very nearly half of the solid crust of the globe, combined as most of it is with the](https://iiif.wellcomecollection.org/image/b21208724_0017.jp2/full/800%2C/0/default.jpg)
