atmosphere

[In Sw. atmosfer; Ger. atmosphäre; Fr. atmosphere; Sp. & Ital. at mosfera; Port. atmosphera; from Gr. ἀτμός ( atmos ) smoke, steam, vapour, and σφαῖρα ( sphaira ) = a ball, a sphere.] 1. Lit. The air surrounding our planet, and which, as the etymology implies, is, speaking broadly, a "sphere" (not, of course, a solid, but a hollow one). With strict accuracy, it is a hollow spheroid. Its exact height is unknown. At 27 miles above the surface of the earth half its density is gone, and the remainder is again halved for every further rise of 2.7 miles. Some small density would remain at forty-five miles high. At eighty miles this would have all but disappeared. But from sundry observations, made at Rio Janeiro and elsewhere, on the twilight are, M. Liais infers that the extreme limit of the atmosphere is between 198 and 212 miles. For its weight, see ATMOSPHERIC PRESSURE. In the lower strata of the atmosphere the temperature falls at least a degree for every 352 feet of ascent; hence, even in the tropics, mountains of any considerable elevation are snow-capped. The atmosphere appears to us blue, because, absorbing the red and yellow solar rays, it reflects the blue ones. It revolves with the earth, but being extremely mobile, winds are generated in it, so that it is rarely long at rest. [WIND.] For its composition, see AIR. Evaporation continually at work sends into it quantities of water in a gaseous state; clouds are formed [CLOUDS], and in due time descend in rain. [RAIN, METEOROLOGY.] The atmosphere always contains free electricity, sometimes positive and sometimes negative. There appears to be no atmosphere around the Moon; but the case seems different with the Sun, Venus, Mars, Jupiter, and Saturn. "How as a talisman of magic fame, This atmosphere conveys th' enlightening beam, Reflects, inflects, refracts the orient ray Anticipating sheds the rising day." Brook: Universal Beauty . (Richardson.) 2. Fig .: Any pervading intellectual, moral, religious, or other influence by which one is surrounded; as in the expre ion, "He lives in an atmosphere of suspicion." * Electrical Atmosphere : An obsolete name for the sphere immediately surrounding an electrified body and operated upon by it. Magnetic Atmosphere: The sphere within which the attractive force of the magnet acts. at-mo-sphèr'-ic, at-mo-sphèr-ic-al, a . [Eng. atmospher(e); -ic, -ical. In Fr. atmo sphérique; Sp. atmosferico .] [ATMOSPHERE.] Pertaining or relating to the atmosphere. Specially 1. Constituting or pervading the atmosphere; made of air. "... the transparent atmospheric envelope..."Herschel: Astronomy , § 566. 2. Existing within the atmosphere. ". but when we reflect that the Cordillera, running in a north and south line, intercepts, like a great wall, the entire depth of the lower atmospheric current "-Darwin: Voyage round the World, ch. xv. "Measure of atmospheric pre ure, Airy : Sound , p. 8. "-Prof. IMG:content-0859.png:[blocks in formation] 357 to produce a near approach to a vacuum in the cylindrical chamber beneath it. Such was Newcomen's engine, constructed in 1705, and subsequently improved by Smeaton, Brindley, and others, till superseded by Watt's single-acting engine, which was a genuine steam-engine. The atmospheric engine was used only for pumping water. Mech.: A line drawn upon an indicator-card by a pencil worked by the steam of a steam engine, and designed to register the equilibrium line between steam pre ure on the piston and the extent of the vacuum produced on the other. The former is indicated by numbers ascending above the atmospheric line; the latter by numbers descending below it; while itself it stands at zero. [INDICATOR-CARD.] atmospheric pre ure. The pre ure exerted by the atmosphere, not merely downwards, but in every direction. It amounts to 14.7 lbs. of weight on each square inch, which is often called in round numbers 15. On a square foot it is = 2,160 lbs., or nearly a ton. It would act upon our bodies with crushing effect were it not that the pre ure, operating in all directions, produces an equilibrium. If any gas or liquid pre upon a surface with a force of 15 lbs. on a square inch, it is generally described as having a pre ure of one atmosphere; if 60 lbs., of two atmospheres; if 120 lbs., of four atmospheres, and so on. atmospheric railway. A railway in which the propulsive force designed to move the carriages along is that of the atmosphere. The notion of such a method of locomotion seems first to have suggested itself, in the latter part of the seventeenth century, to the French physician, Papin, whose name is for ever a ociated with the celebrated digester. [DIGESTER.] In 1810 Mr. Medhurst published a work entitled A New Method of conveying Letters and Goods by Air . His proposal was to construct a closed tunnel, in which the carriages-the last of them provided with a piston fitting the tunnel-should be propelled by air forced in behind then. Vallance, of Brighton, in 1825, recommended as an improvement on this plan the exhaustion of the air in front. About 1835 Mr. Henry Pinkus, an American gentleman residing in England, patented a scheme for placing the carriages in the open air, but connecting them below with a small tunnel, having a narrow slit above, with ingeniously-constructed apparatus to render the tunnel temporarily air-tight notwithstanding the slit. Not much was done to carry out the patent; and Pinkus's scheme of what he called a Pneumatic Railway was considered as having failed, when, in 1840, Me rs. Clegg and Samuda brought forward a somewhat similar project under the name of the "Atmospheric Railway." An experimental fragment of line laid down near Wormwood Scrubs, on the Great Western line, was succe ful, as was one designed for actual use from Kings town to Dalkey, in Ireland, another between London and Croydon, and a third in South Devon; all, however, have been since abandoned. For pa engers at least, and to a great extent even for the transmi ion of letters, the railways of the ordinary type, on which steam is the impelling force, have triumphantly held their own against the innovation of the Atmospheric or Pneumatic Railway, and all that now remains of the latter method of propulsion are the pneumatic dispatch tubes, used in London, and recently introduced in some American cities, for transmitting mail and parcels to short distances. [PNEUMATIC.] atmospheric tides. Tides which must exist in the atmosphere as they do in the ocean, from the attractions of the moon and the sun. a-tô, adv. [Arwo.] ( Scotch.) a'-tok, s. [South American name.] Zool. A variety of the Mephitis American a found at Quito, whence Humboldt called it Gulo Quitensis. It is sometimes termed the Zorra.