When, too, the tranquil hourly motion of the needle is disturbed by a magnetical storm, the perturbation frequently proclaims itself over hundreds and thousands of miles, simultaneously, in the strictest sense of the word-or it is propagated gradually, in brief intervals of time, in every direction over the surface of the earth. With amazement should we see that the tremblings of two small magnetic needles, were they suspended deep in subterraneous space, would actually and accurately measure the distance that intervenes between them. There are regions of the earth where the mariner, enveloped for many days in deep mist, without a glimpse of the sun or the stars, and without, in fact, any other means of ascertaining the time, can still accurately determine the hour by the variation of the dip of the needle, and can ascertain whether he be then sailing to the north or south of the port towards which he would steer his course.

Each of these three phenomena is itself a fertile subject for close research and untiring observation. On each of them, or their combination, and their connexion with electrical changes, are some of our most eminent philosophers engaged, and important theoretical and practical discoveries have already resulted from these laborious studies. It is probable that few of those who cross the sea are at all aware of the untiring patience with which numerous observers are working for the advancement of this science, at various magnetic stations. An illustrious philosopher of our own isle has calculated that the mass of observations which will be accumulated in the course of only

three years, will 1,958,000!

amount to no less than

With reference to magnetic charts, it may be briefly stated that Dr. Halley, in 1701, after having made many personal observations on the variation, or declination, of the needle in different parts of the Atlantic and Pacific Oceans, published a chart, in which were traced what have since been termed isogonal or isogonic lines, that is, lines passing through the points on the earth's surface where the magnetic variation was the same; and other charts of a like kind have since been constructed at different times. It was once thought that such a chart might serve as the means of ascertaining the longitude of a ship at sea, by an observed variation of the needle. Adolph Erman, after a journey through the whole length of the Russian Empire, determined the position of the isogonal lines, from his own and other authentic observations between the years 1827 and 1830. He published a variation chart, showing the principal lines in the two hemispheres of the earth projected stereographically on the plane of the equator. In another chart, similarly projected, are represented the principal lines of equal magnetic intensity (isodynamic lines) from the table and chart of colonel Sabine. Dr. Brewster has also devoted attention to the subject, and constructed a chart. Thus, as in the case of climatic science, numerous observations have been collected and expressed on charts, which will gradually become more and more perfect, until valuable practical results may be derived from them.

CHAPTER III.

THE OCEAN.

As the traveller enters his vessel, he is embarking on a sea of unknown and hitherto uncounted wonders. This ocean is the great bond of the world, the silver girdle which encircles the globe; and it is studded like a precious bracelet with innumerable pearls, and glistening gems of unsurpassed lustre. Its beautiful shells of delicate hues and most intricate chambers are floating in the upholding waves, and here and there, on the barren shores, are cast the fragile fabrics that the nicest art of man could neither contrive nor construct. Then the gliding fishes of the far rolling ocean, how numerous, how skilfully adapted to their element are they! You sail in your rapid bark over a populous world of everdarting tribes, that shoot like arrows from a strong bow, through the yielding waters. They disturb you not, and you disturb not them. They seek their permitted prey, they escape or defend themselves, all without the aid of haughty man, and solely by the curious modes and provisions with which their Maker has furnished them. Thousands of them are darting under the keel of your vessel, thousands both small and great; and each one of them is provided with a perfect frame, and with the most minute and exquisite adjustments for breathing, for rising and sinking,

for cleaving the liquid element, for guiding itself, and for obtaining its own peculiar food.

Also there are, besides the innumerable swimming things, wide-spreading fields of sea-plants. Each of these is also complete in its lower scale of fabric. Not only is the land adorned with plants, most beautiful plants also exist in the ocean; and with these, as marine productions, we may class those exquisite corals which are so striking even to the commonest observer. What delicate branchings, what minute net-work, what innumerable and finely-arranged pores, do these exhibit! And there are islands, and long stretching reefs, of massive coral !

All who have voyaged long upon the open sea, will have observed how many and powerful superstitions rule over the sailors, and even their superiors in station. This, which is commonly a subject for passing amusement to us, suggests the reflection that it may arise from a cause worthy of our attention. When we are far from home, on the great deep, we see nothing of the works of man. We are indeed sailing in a machine of his construction, but even in its varied management we become conscious of the mere dead machine that it is, without the favouring breeze of heaven. Framed fitly together from the trees hewn down by man; furnished with every cord, and mast, and flying sail that may promote its rapid advance, or sustain its safe equilibriumyet the whole is but a mere and manifest instrument, adapted by nature to the use of man. When she smiles, the course of the vessel is prosperous; when she frowns, the ponderous

machine, with all its dead and living furniture, becomes her mere plaything, the flying game of the laughing winds, and the light sport of the scornful billows! Then it is that every human being the ship contains becomes tremblingly aware of the dependence of his situation on the God of nature. He has not a firm spot on which to plant his foot, nor a calm and powerful companion on whom to rely. His friend of highest wealth and rank is as much at the mercy of the elements as his meanest servant. "Their soul is melted because of trouble.—Then they cry unto the Lord in their trouble, and he bringeth them out of their distresses."-Psa. cvii. 26-28.

Even in the calm, and with the friendly breeze lightly heaping its favours upon him, even then, apart from the vessel itself, there is not a visible object which owns man for its maker, or upholder, or master. He cannot command the rise, or the course, or the breaking of one single billow; he cannot remove one single rock that rises up before him, or sleeps dangerously close under him; he cannot in the slightest degree influence the force or the direction of one single current that runs through the ocean, or one single wind that flies over it. All is the direct and constant work of Heaven. The Almighty seems to have reserved the seas to himself. All the inhabitants of their depths are totally dissimilar to man in frame, and appearance, and habits. On the land, man is a petty monarch; there he can hew down the forest, drain the lake, direct the course of the river, throw the many-arched bridge over its waters, clear the incumbered soil, encourage,

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