This appearance, so alarming to the Spaniards, is that deviation from the meridian which is called the variation of the needle, and is different in different parts of the world; being west at some places, east at others, and in parts where the variation is of the same name its quality is very different. Sebastian Cabot is generally allowed to be the first, who, about the year 1497, more accurately ascertained the reality of this variation, and that it was the same to all needles in the same place. For a long time after, it was thought to be invariably the same, at the same place in all ages; but Mr. Gellibrand, about the year 1625, discovered that it was different at different times in the same place. From subsequent observations, it appears, that this deviation was not a constant quantity, but that it gradually dimi nished; and, at last, about the year 1660, it was found that the needle pointed due north at London, and has ever since been increasing to the westward of the north. It appears, therefore, that in any one place, the variations have a kind of libratory motion, traversing through the north to certain limits eastward and westward and indeed vacillating a little daily.

To return to the magnet, it has been observed, that no substance interposed between it and iron, can prevent the action of its attractive energy. All metals (iron excepted) wood, glass, fire, water, and even men and animals, afford a free passage to its influence. It has been observed, moreover, that of two magnets the north pole of the one attracts the south pole of the other, and repels its north pole; while, on the contrary, the north pole of the second was attracted by the south pole of the first, which repelled constantly the south pole of the second. The

See Adams on Electricity; and for an ample account of the Theories of the Variation of the Compass, see the Treatise on Magnetism in Haüy's Natural Philosophy.

attractive tendency in iron and a magnet is also reciprocal; and they are often attached to each other with such force as to require a considerable weight to separate them.

Among the various hypotheses that have been framed to account for the phenomena of magnetism, I shall only mention that of Mr. Euler; who supposes that the two principal causes, which concur in producing the wonderful properties of the magnet, are, first, a particular structure of the internal parts of the magnets, and of magnetical bodies; and, secondly, an external agent or fluid, which acts upon and passes through these pores. This fluid he supposes to be the solar atmosphere, or that subtile matter called ether, which fills our system. But I shall not here expatiate upon theories, which, however ingenious, are allowed to be unsatisfactory. We know that gravitation, electricity, and magnetism exist; that they have certain properties; and are productive of certain phenomena: but what their nature is, what their secondary causes, is still among the mysteries, which will, perhaps, be for ever inexplicable. The Contemplative Philosopher will acquiesce in his ignorance with the most awful and devout sentiments of admiration! And, in every view of the material creation, as well as of the moral government of the Divine Being, he may exclaim, in the language of holy writ, Öthe depth of the riches both of the wisdom and knowledge of God! how unsearchable are his works, and his ways past finding out !-Of him, and through him, and to him are all things: to whom be glory for ever. Amen.'

No. LIII.

ON EARTHQUAKES.

Hæc deorum immortalium vox putenda est, cum agri terræ motu quodam contremiscunt, et inusitato aliquid sono incredibilique prædicunt.

Towers, temples, palaces,

Flung from their deep foundations, roof on roof
Crushed horrible, and pile on pile o'erturned,
Fall total.

CICERO.

MALLET.

THE greater and more formidable phenomena of Nature, whatever modern philosophers may attribute to second causes, were considered by the ancients as the immediate voice of the immortal gods, and the forerunners, in course of some extraordinary event. And thus the Roman orator expresses himself above.-But whether we regard the sentiments of the ancients as the result of rational piety or apprehensive superstition; or whether we consider the most tremendous phenomenon as capable of being explained upon philosophical principles; there is certainly no reason to doubt, that the Omnipotent Being, who first subjected the material world to the influence of certain invariable laws, may so direct the concurrent operations of natural causes, as to evince that he has not left his creation to the fortuitous consequences of Chance, or the irresistible impulse of Necessity; but that even in this sublunar state, the various revolutions, not of empires only, but in the face of the great globe itself, are so many indications, that he incessantly exercises a moral government over his creatures; and that, in the wise dispensations of his providence, every event will finally appear to have been conducive to his gracious

designs, which are the good and happiness of the whole. Earthquakes, therefore, and all other dreadful phenomena, may be considered, in this light, as the immediate operation of the Deity. He looketh on the earth, and it trembleth: he toucheth the hills, and they smoke."

His hand the lightning forms:

He heaves old Ocean, and he wings the storms.

POPE.

Earthquakes, which are unquestionably the most dreadful phenomenon of Nature, have not been confined to such countries, as, from the influence of climate, their vicinity to volcanic mountains, or any other cause, have been considered as more particularly subject to them; but their effects, although not in any degree so extensive and calamitous, have been often felt in this island. I purpose to inquire, in this paper, into the theory and causes of these phenomena, of which the history of all ages and countries has afforded such terrible examples; examples so numberless, indeed, as to justify the emphatical saying of an ancient writer, that we walk upon the carcasses of cities, and inhabit only the ruins of our globe.'

The globe around earth's hollow surface shakes,
And is the ceiling of her sleeping sons.

O'er devastation we blind revels keep;

Whose buried towns support the dancer's heel.

YOUNG.

Poetry does not confine its descriptions to the beautiful and pleasing: it selects some of its richest subjects from the grand and majestic, and even from the tremendous and terrific. Dr. Grainger, in his beautiful poem, the Sugar Cane, gives a terrible, but picturesque description of an earthquake in the West Indies, where that phenomenon is very frequent.

Earthquakes, Nature's agonizing pangs,
Oft shake th' astonied isles; the solfaterre

Or sends forth thick, blue, suffocating steams;
Or shoots to temporary flame. A din,
Wild, thro' the mountain's quivering rocky caves,
Like the dread crash of tumbling planets, roars.
When tremble thus the pillars of the globe,
Like the tall coco by the fierce North blown,
Can the poor, brittle tenements of man

Withstand the dread convulsion? Their dear homes
(Which shaking, tottering, crashing, bursting, fally
The boldest fly; and, on the open plain
Appalled, in agony, the moment wait,

When, with disrupture vast, the waving earth
Shall whelm them in her sea-disgorging womb.
Nor less affrighted are the bestial kind.
The bold steed quivers in each panting vein,
And staggers, bathed in deluges of sweat:
The lowing herds forsake their grassy food,
And send forth frighted, woful, hollow sounds:
The dog, thy trusty centinel of night,

Deserts his post assigned, and, piteous howls.
Wide ocean feels.

The mountain waves, passing their customed bounds,
Make direful, loud incursions on the land,

All over-whelming: sudden they retreat,

With their whole troubled waters; but, anon,

Sudden return, with louder, mightier force;

(The black rocks whiten, the vext shores resound;)
And yet, more rapid, distant they retire.

Vast coruscations lighten all the sky,

With volumed flames; while Thunder's awful voice,
From forth his shrine, by night and horror girt,
Astounds the guilty, and appals the good.

And Mr. Mallet, in his fine poem, the Excursion, has taken a view of that midland part of Europe, which has been so repeatedly the scene of the most dreadful devastations: I mean Italy and the neighbouring island of Sicily. He introduces a description, replete with the most awful imagery, of a city on the point of being swallowed up by an earthquake; and he expatiates at length upon the signs that precede it, as well as upon its causes and effects. But as the limits of my paper will not permit me to insert this description, I shall proceed immediately to the dif