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Chap.
Sect. vii. Various Fiery Meteors, with Balls that have de.
scended to the Earth

457 viii. Observations on Fire-Balls

460 ix. Aërolites, or Meteoric Stones

468 1. General History and Observations

ib. 2. Lunar, or Selenitic Origin of Meteoric Stones 475 x. Falling or Shooting Stars

492 XLVII. On Luminous and Burning Exhalations under

the Names of Ignes Fatui; Will-o'-the-
Wisps; Jack -0. Lanthorns; Mariner's
Lights; and St. Helmo's Fires

494 Sect. i. General Remarks

ib. ii. Of the Ignis Fatuus, as observed in England 498 iii. Luminous and Inflammable Exhalations on the Snows of the Appenuines

501 iv. Fiery Exhalations or Damp, that set on Fire various Hay Ricks in Pembrokeshire

502 XLVIII. On Atmospheric Deceptions, Fata Morgana,

Mirages, Glamer or Looming, Ilalos, Mul-
tiplicd Rainbows; Parhelions and Parasele-
nítes, or Mock-Suns, and Mock-Moons;

Glories; Refraction of Iceland Crystal 504 Sect. i. Explanation of the principle of Atavospheric Deceptions

ib. ii. Fata Morgana; or Optical Appearances of Figures in the Sea and Air, in the Faro of Messina

509 iii. Singular Instance of Atmospherical Refraction, by

which the Coast of Picardy was brought apparently
close to that of llastings

514 iv. On Refractions and Louble Refractions in the Atmo. sphere

516 v. Farhelia, or Mock.Suns, seen at Dantzic

521 vi. Pyramidal Arpearance in the Heavens, observed in Essex

522 vii. Parhelia at Sudbury, Suffolk ,

523 viji. Two Mock-Suns and an Arc of a Rainbow in. verted

524 ix. Beautiful Irridescent Arches in a Mist

526 x. Peculiar Solar and Luras Irises in South America

528 xi, Lunar Rainbow in Derbyshire

529 xii, Description of a Glory on Mount Realt, near the Vale of Clwyd

530 XLIX. Of Sounds and Echoes

593 Sutt. i. General Observations on the Nature of Sound, Whispering Domes, and Echoes

ib. ii. Extraordinary Whispering Places and Echoes

546 iii. Singular Sympathetic Action of Two Pendulum

Clocks on each other

547

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We now advance to the atmospherical phænomena of the science of Geology, in the extensive sense in which we have em. ployed this term; and shall proceed to a brief survey of whatever is most curious or worthy of observation in the composition of the Atmosphere; the variation of Climate; the extremes of Heat and Cold; the existence of Electricity and electric Powers, as Thunder and Lightning, Aurora Borealis, Water-spouts ; Falling-stars, and Ignes Fatui ; Echoes, Wind, Hurricanes, and Storms; the origin of Mist, Dew, Sleet, Snow, Mirages, or Fata Morgana, Meteoric, Stones, and various other appearances connected with or depen. dent upon the preceding; and which collectively constitute the Science of Meteorology.

VOL, IV.

CHAP. XXXV.

: GENERAL NATURE OF THE ATMOSPHERÉ.

The atmosphere is that invisible elastic fluid which surrounds the earth to an unknown height, and incloses it on all sides. It was thus denominated by the Greeks in consequence of the vavours which are continually mixing with it, or combined in it*. Iu contemplating the nature of the atmosphere there are two points of considerable importance to be attended to, respecting which therefore we shall offer a summary of the best established facts and opinions of the present day; and these are the materials that enter into its composition, and the changes to which it is liable.

SECTION 1.

Composition of the Atmosphere. Neither the properties nor the composition of the atmosphere seems to have occupied much of the attention of the ancients. Aristotle considered it as one of the four elements, situated be. tween the regions of water and fire, and mingled with two exha. lations, the dry and moist; the first of which occasioned thunder, lightning, and wind; while the second produced rain, snow, and hail. The ancients, in general, seem to have considered the blue colours of the sky as essential to the atmosphere; and several of their philosophers believed that it was the constituent principle of other bodies, or at least that air and other bodies are mutually convertible into each other. Thus Lucretius :

Semper enim quodcunque fluit de rebus, id omno
Aeris in magnum fertur mare: qui nisi contra
Corpora retribuat rebus, recreetque fluenteis,
Omnia jam resoluta forent, et in acra versa.
Haud igitur cessat gigni de rebus et in res
Recidere assidue, quoniam fluere omnia constat.

Lib. v. 274.

• From århus, a vapour, and paipa,

re.

All that pours profuse
From things, perpetual, the vast ocean joins
Of air sublime ; which if to things again
Paid not, thus ballancing the loss sustain’d,
All into air would dissipate and die.
Hence, born from things, to things air still returns
Ceaseless, as prove their fluctuating forms.

Good.

But these opinions continued in the state of vague conjectures, till the matter was explained by the sagacity of Hales, and of those philosophers who followed his illustrious career.

It was not till the time of Bacon, who first taught mankind to investigate natural phenomena, that the atmosphere began to be investigated with precision. Galileo introduced the study by pointing out its weight; a subject which was soon after investigated completely by Torricelli, Paschal, &c. Its density and elasticity were ascertained by Boyle and the Florence Academicians. Ma. riotte measured its dilatability; Hooke, Newton, Boyle, Dera ham, pointed out its relation to light, to sound, and to electri. city. Newton explained the effect produced upon it by moisture; from which Halley attempted to explain the changes in its weight indicated by the barometer. But a complete enumeration of the discoveries made upon the atmosphere in general belongs to pneumatics; a science which treats professedly of the mechanical pro. perties of air.

The knowledge of the component parts of the atmosphere did not keep pace with the investigation of its mechanical properties. The opinions of the earlier chemists concerning it are too vague and absurd to merit any particular notice. Boyle, however, and his contemporaries, put it beyond doubt that the atmosphere con. tained two distinct substances. 1. An elastic fluid distinguished by the name of air. 2. Water in a state of vapour. Besides these two bodies, it was supposed that the atmosphere contained a great variety of other substances, which were continually mixing with it from the earth, and which often altered its properties, and rendered it noxious or fatal. Since the discovery of carbonic acid gas by Dr. Black, it has been ascertained that this elastic fluid always constitutes a part of the atmosphere. The constituent parts of the atmosphere therefore are,

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