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flected by other clouds, and whose thunders are repeated in their echoes. Experienced seamen have more than once been deceived by similar appearances. Whatever it might have been, all this fantastic representation of magnificence and terror, all these mountains surmounted by palm-trees, the storms which raged on their summits, the river, the bridge, dispersed on the arrival of night, like the illusions of the world on the approach of death. The star of the night, the triple Hecate, which repeats in softer harmony the pictures of the day, dissipated, as it rose above the horizon, the empire of light, and substituted the reign of shadows. Not long afterwards innumerable stars, presenting an eternal éclat, shone out in the midst of darkness. Oh, if daylight is in itself but an image of life; if the rapidly fleeting hours of the dawn, the morning, noon, and night, represent the fugitive years of infancy, youth, virility, and old age, surely death, like the night, ought to reveal to us new skies and new worlds!

B. DE ST. PIERRE: Harmonies of Nature.

[Since this was written by St. Pierre, the mirage has been frequently seen on the desert as well as the ocean.]

THE AURORA BOREALIS.

TRUSTWORTHY reports, the result of careful investigations, agree in assigning to the magnetism of the globe and the electro-magnetic forces the productions of the

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THE AURORA BOREALIS.

polar light as well as the heat of our planet, whose magnetic points may be regarded as frigid poles. We must not treat the aurora borealis as the cause of a perturbation in the equilibrium of terrestrial magnetism, bùt simply as the result of a terrestrial activity whose power extends to the creation of luminous phenomena. The appearance of the aurora borealis is the act which puts an end to a magnetic storm, just as in electric storms another brilliant phenomenon, the lightning, announces that the equilibrium, temporarily disturbed, has reëstablished itself in the distribution of electricity.

In order to present in a single picture all the features of the phenomenon, we must describe the several phases of development which signalise a complete aurora borealis.

Above the horizon, towards the magnetic meridian of the point of observation, the sky, at first pure, begins to darken. A nebulous veil is then gradually formed, which slowly rises, and at length attains a height of eight or ten degrees. Through this obscure segment, the colour of which changes from brown to violet, the stars may be distinguished as in a thick fog. A little later, an arch is formed on the edge of the segment, white at first, then yellow, but always of a dazzling brilliancy. Sometimes this luminous bow appears to be agitated for hours together by a sort of effervescence and a continual change of form, before it darts forth rays and columns of light, which reach the zenith. Then the emission of the polar light becomes intense, and equally vivid are its colours, which, from a violet and a bluish

THE AURORA BOREALIS.

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white, pass through all the intermediate shades to a green and a purple red. It is the same with the electric sparks. Their hue is dependent on the force of the tension and the violence of the explosion. Sometimes the columns of light appear to spout from the brilliant arch mingled with dark rays resembling a thick smoke. Sometimes they rise on different points of the horizon, and then combine in one vast sea of flames, the splendour of which the very best painter might vainly endeavour to depict, for each moment witnesses a rapid change in the undulations and the form and brilliancy of the ensemble. At certain moments the fierceness and intensity of the light, heightened by the rapidity of the magnetic action, render the coruscations and undulations of the aurora borealis perfectly visible in broad day.

Around the point which corresponds in the sky to the direction of the magnetised needle, lightly poised on its centre of gravity, may be seen-when the phenomenon acquires its fullest development—an assemblage of rays forming what is called the crown of the aurora borealis. It resembles a species of brilliant celestial daïs, composed of a soft and powerful light. It is rare that the appearance of the aurora is sufficiently complete, or prolonged until the crown is formed; but when the perfection does happen to be realised, it announces the termination of the phenomenon. From that moment the rays become rarefied, abridged, and discoloured. The crown and the luminous arch dissolve themselves, and presently little is to be seen upon the celestial vault but large, motionless,

C