CHAPTER XII.

COMETS.

Discriminating Features-Scene on the Essequibo-Technical Terms-Popular Superstitions-Comet of 1811-Varying Forms of Comets-Instances of Brilliance-Nuclei and Tails-Extraordinary Dimensions-Physical Constitution of Comets-Their Number-Orbits-Comet of 1680-Its History-Halley's Comet-Return Predicted-Lagrange, Clairaut, MessierReturn verified-Second Return-Story of Halley's Comet - Encke's Comet-Resisting Medium-Biela's Comet-Passes near the Earth's Path -Comet of 1843-The Expected Comet-Supposed Past Visits-False Alarm-Probability and Consequences of Collision.

We have now to consider a very numerous class of bodies of perfectly mysterious constitution and office, some of which are permanently fixed in the solar system, while others are attached to it as periodical visitors, and the majority appear within its limits, retire into the immensity of space, and return no more. Comets, as these bodies are called, are readily distinguished from the planets by several peculiarities. The light by which they shine is in general comparatively pale. They vary in form from globular luminosities to irregular wisp-like shapes; and often totally change their aspect. They either move in immensely elongated ellipses, only one end of which lies within the visible limits of the system, in the majority of cases; or they pass through it in parabolas and hyperbolas-open curves which never return into themselves. While also the planets revolve nearly in the plane of the ecliptic, comets cut it in every direction, and approach the sun from all parts of surrounding space. Their

motion, likewise, is often retrograde, or from east to west, while that of the planets is invariably from west

to east.

Early in the year 1843, a scientific European traveller was ascending the course of the Essequibo, one of the noble rivers in the great forest region of South America, with a party of native Indian attendants. For several weeks no sight was gained of either sun, moon, or stars, as a uniform mass of greyish clouds veiled the sky, and the rain descended in torrents. But one evening, while preparing to bivouac for the night, the clouds cleared off towards the south-west, and exposed the deep tropical blue spangled with stars. There was also visible a broad, white, nebulous band, inclining towards the horizon, and stretching half way towards the zenith, the pearly whiteness of which strongly contrasted with the well-developed neighbouring azure. Whether the band apparently rested on the horizon could not be ascertained, as the walllike forest, near the edge of which the party was encamped, prevented that portion of the heavens from being seen. Sir Robert Schomberg the traveller in question, gazed with amazement upon the object; but soon recognised a comet. His Indian friends looked askance at him, while intently marking the phenomenon themselves. The scene was calculated to fix itself firmly in the memory. Upon a small island in the middle of the river, surrounded by foaming waters, which, opposed in their course by dykes of granite, went thundering away over the black, stony masses, stood a single European, arrested by "a wonder in heaven," in the midst of naked savages, equally impressed, the coppery hue of whose bodies was strongly brought out as the camp-fire threw its gleam upon their figures.

Some stood upright, with arms folded across the breast; others squatted upon the ground; but all eyes were directed to the celestial novelty. For a time no word was spoken, and no sound was heard, but the rush of the struggling stream. At last one broke the silence. "This," said he, "is the spirit of the stars, the dreadful Capishi-famine and pestilence await us." Another called it Cá-poéséiná, "a fiery cloud;" a third, Wa inopsa, "a sun casting its light behind ;" and, as if they had only wanted the utterance of a syllable to give vent to their feelings, the assembled Indians burst into a torrent of declamation, bewailed the appearance of the dreadful Capishi as the precursor of misfortune, and raised with violent gesticulations their arms against the comet.

It must be acknowledged that the terms applied to the apparition by these children of nature are far more picturesque and expressive than those in use with the civilized nations. Our word comet, derived from the Greek, literally signifies "a hairy star," and alludes to the supposed resemblance of the nebulous fringe to the human hair. In defining the details of what may be considered a fully developed cometary body, we speak of a roundish nebulosity as the "head" of the object; of a conspicuous stellar point in it as the "nucleus," answering to a kind of bright central eye, and of a luminous train attached as the "tail." Formerly, the latter appendage was only known as the tail when it follows the head, as when the comet is approaching the sun, while, on receding from the sun, when the train precedes the head, the queue, or pig-tail, became in popular speech the "beard." This position of the appendage is general, but not invariable. The Chinese call it indifferently the "brush." Some of our early

writers speak of "shode stars," meaning comets, the term shode being a provincialism for hair. Not a whit better are the phrases of Pliny, referring to diversities of form, as "tun-like," "horn-like," " quoit-like," and "horse-mane-like."

It must be admitted, also, that barbarous tribes have not been singular in viewing unusual appearances in the heavens as harbingers, presages, or causes of terrestrial events, generally of the startling or disastrous class. Civilized communities have been just as prone to the same superstition as the Indians of the Essequibo; and have often been frightened out of their propriety by it. Our national poetry abounds with allusions to the dread portentousness of cometary appearances. Thus Milton fanned the popular prejudice:

"Satan stood

Unterrified, and like a comet burn'd,

That fires the length of Ophiuchus huge,
In th' arctic sky, and from its horrid hair
Shakes pestilence and war."

Byron has likewise

"A pathless comet, and a curse,
The menace of the universe."

A formidable bill of indictment, enumerating high crimes and misdemeanours, appears in the

pages

of an

Threat'ning the world with famine, plague, and war;
To princes, death; to kingdoms, many crosses;

To all estates, inevitable losses;

To herdsmen, rot; to ploughmen, hapless seasons;
To sailors, storms; to cities, civil treasons."

But some good as well as evil, and various events of the ambiguous class, have been referred to cometary influence. Popular impressions respecting the supposed terrestrial effects of the comet of 1811--a fine

object in the autumn of that year, still well remembered
by many-are on record. It was gravely noted,
that wasps were very few in number; that flies became
blind, and disappeared early; and that twins were
born more frequently than usual. The season was
remarkable for its bountiful harvest and abundant vint-
age. Grapes, figs, melons, and other fruits, were not
only produced in extraordinary quantity, but of de-
licious flavour, so that "comet wines" had distinct
bins allotted to them in the cellars of merchants, and
were sold at high prices. There is, however, no fact
better attested, by a comparison of observations, than
that comets have no influence whatever in heightening
or depressing the temperature of the seasons.
fine fruits and ample harvest of the year in question
were, therefore, coincidences merely with the celestial
phenomenon, without the slightest physical connexion
with it. The Ettrick Shepherd apostrophized the ob-
ject in the following lines:-

"Stranger of heaven, I bid thee hail ;
Shred from the pall of glory riven,
That flashest in celestial gale,

Broad pennon of the King of heaven.

"Whate'er portends thy front of fire,

And streaming locks so lovely pale;
Or peace to man, or judgments dire,
Stranger of heaven, I bid thee hail."

The

Though the advanced civilization of recent times has led to juster views of cometary apparitions than to regard them as divinely-appointed omens of terrestrial calamity, yet society is apt to be nervous respecting these bodies, as likely to cause some great natural convulsion by collision with our globe, a point to which reference will be hereafter made.

The three prominent features of comets-a head, nu