Physics of the Terrestrial Environment, Subtle Matter and Height of the Atmosphere. Eric Chassefiere. Читать онлайн. Newlib. NEWLIB.NET

Автор: Eric Chassefiere
Издательство: John Wiley & Sons Limited
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Жанр произведения: Биология
Год издания: 0
isbn: 9781119866152
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La Hire, after Kepler, to use an older, simpler and safer method to find the height of the atmosphere: this method is based on the observation of the twilight hours.

      We will return to the twilight method. The essential fact here is the inference, from the confrontation between pressure measurements made at different altitudes on the mountains and measurements of the relationship between air dilatation and pressure made in the laboratory, of the existence at great heights of air following a law of expansion different from that of the air that directly surrounds us. Thus, the heterogeneous lower air and the elementary upper air do not only differ in their densities, the former being much heavier than the latter because of its load of impurities emanating from the Earth, but also in their nature, the latter extending much higher than it would if it followed the law of expansion of the former. It should be noted that the entry REFRACTION from the Encyclopédie no longer makes any reference to the role of vapors and exhalations, which is emphasized in the Dictionnaire Universel. As we will see, the role of atmospheric impurities in refraction was disproved at the beginning of the 18th century on the basis of observations showing its absence under certain conditions, such as the case of a star seen through a cloud, which led some scientists to postulate the existence of a subtle, lightweight refractive matter. An allusion to refractive matter can be found in the entry REFRACTION of DUF-1727:

      The cause of refraction is not yet known; perhaps it will never be known, like many other points in physics. Is it air, is it refractive matter that is in the air, according to Mr. Cassini’s conjecture? This is where we are still on this matter. There are lot of apparent annoyances in one or the other system, and consequently a lot of uncertainties.

      The existence of refractive matter was far from being unanimously accepted. It is not mentioned in the entry REFRACTION of the Encyclopédie.

      The example of the aeolipile, where water is sufficiently rarefied by fire, comes out with a sharp whistle, in the form of a matter perfectly similar to air; but soon afterwards loses this resemblance, especially in the cold, and becomes water again through condensation, as it was originally. The same behavior can be observed in the spirit of wine, and other subtle and fleeting spirits obtained by distillation; instead of the real air being reduced neither by compression, nor by condensation or any other means, to any substance other than air.

      So you can make water take on the appearance of air for a while: but it soon regains its own.

      We find the same questioning expressed in the entry for ÉBULLITION (BOILING) in the Encyclopédie:

      Air is divided into “real or permanent” and “apparent or transient”. The vapors, produced by evaporation of water, are apparent air, while dry exhalations are permanent air. Air is to be understood here in the sense of coarse or heterogeneous air, a mixture of elemental air and impurities emanating from the Earth and water. The production of air from solid bodies that appear to be devoid of air is questioned by the author of the entry AIR in the Encyclopédie:

      But, after all, there is still reason to doubt whether the matter thus extracted from solid bodies has all the properties of air; whether this air is not transient, or whether the permanent air that is drawn from bodies did not already exist there. Mr. Boyle proves through an experiment conducted in the pneumatic machine with a lit wick, that this subtle smoke, which the fire raises even from dry bodies, does not have as much spring as air, since it cannot prevent the expansion of a little air enclosed in a bladder which it surrounds […] Nevertheless in some later experiments, by dissolving iron in vitriol oil and water, or in etching, he formed a large air bubble which had a real spring and which, as a result of its spring, prevented the neighboring liquor from taking its place; when a warm hand was applied to it, it expanded easily like any other air, and separated in the liquor itself into several bubbles, some of which rose out of the liquor in the open air.

      The same physicist assures us that he has drawn a truly elastic substance from several other bodies; such as bread, grapes, beer, apples, peas, beef, etc. and from a few bodies, by burning them in a vacuum, and singularly from paper, from deer horn: but nevertheless this substance, on close examination, was so far from the nature of pure air, that the animals enclosed in it, not only could breathe only with difficulty, but even died there faster than in a vacuum, where there would have been no air at all.

      A modern author sees the atmosphere as a great chemical vessel, in which the matter of all species of sublunar bodies floats in large quantities. This vessel is, he says, like a great furnace, continuously exposed to the action of the Sun; from which it results an innumerable amount of operations, sublimations, separations,