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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![Tlic effects of mixture of invisible steam of differeiit 1eiii])eratures, of visible steam at dittereiit temperatures, and of each of these in dif- ferent electrical states. The growth of size, and the color, of the steam particles and the effects of absence and presence of much dust or smoke. The true results of the electrification of jets of steam or cloudy masses, the relation of the size of the deposited vapor particles to the electrification, and the optical effects of various degrees of electrifica- tion in air. The efiect of an electric field on the surface tension of drops of water, and the various eflects of varying amounts and proximity of the elec- tricity of the charged surface on drops of different sizes. When the electrical field is uniform tlie surface tension of the drop is only slightly diminished, and the diminution is independent of the size of the drop. Very small drops thus preserve their high surface tension in the neighborhood of an electric field. But when there are a number of charged atoms surrounding the droplets the effect is different; the diminution of surface tension which is brought about varies inversely as the square of the radius of the droplet. The whole subject of the electrification of gases, dry and moist, the electrification of drops of water and their behavior under electrification, and the relation of sur- face tension in cloud globules and drops to electricity in natural condi- tions, requires investigation. The cloudy condensation of steam, and the optical effects in electrified steam have hitherto led to conflict- ing inferences, and careful observation has not yet proved a diminution or increase in the size of the water particles or a recombination of dis- sociated molecules of oxygen and nitrogen. The question is of great interest in many respects, and may have a bearing on thunderstorms, rainfall, evaporation, and chemical problems. Shortly stated, there are three principal views of the apparent action of electricity on steam. Mr. Aitken believes that the thick con- densation, coloration, etc., of a jet of electrified steam is due to the prevention of the coalescence of the very small condensed particles which would occur without electrification. Mr. Bidwell believed that the effects were produced by the conglomeration under electric excite- ment of particles which would otherwise have evaporated unseen, not becoming large enough to cause visible obstruction of light. These views are related to Lord Eayleigh's discoveries on the behavior of drops under electrification; the drops coalesced when weakly, and repelled each other when strongly electrified. Prof. Paul Cams holds a very different view, and considers that the condensation effects depend on the action on steam of exceedingly small particles of dust. One may estimate, he says, that pure dust-free, unconfined steam at 100^ would require a pressure of 10 or more atmospheres to condense it. Add to this dust particles less than 0.000001 centimeter in diameter, and the pressure sinks to 15](https://iiif.wellcomecollection.org/image/b21208724_0131.jp2/full/800%2C/0/default.jpg)
