volving kaleidoscope. Objects of fixed refracting properties exhibit fixed colours, and objects of changeful refracting properties exhibit changing colours; the former class of objects abound most on the ground, and the latter class abound most in the air; and hence all the well-known beauteous characteristics of the tinting of land and cloud and sky. But there is one prevalent arrangement in the general results of refraction which singularly combines magnificence with usefulness, and both with benignity. The violet ray of the sunbeams which break in their progress through the atmosphere, that ray which develops the greatest quantity of heat, and which, if it came floodingly down, might fall on all breathing creatures with the suffocating warmth of a simoom,—is so easily and eminently refrangible, that it greatly deflects in the very highest regions of the air, and at length goes so far aside as very rarely to reach the ground, or become apparent to the eye. The indigo and the blue rays, which are next in refrangibility, go off at just so much less a slant, and at just so much lower an altitude, as to be commonly the highest rays visible, and therefore to form the predominant colour of the sky. And how superb is their azure, how luscious to the eye, how grand and fit a setting to the star-gems of the heavens! The green ray, situated in the middle of the spectrum, and the yellow ray, situated next to it, are the rays most abundantly reflected by the herbage of the ground and by the leaves of trees; and therefore they form the predominant dyes of the land's carpet, the verdure of luxuriant pastures and waving forests, and the creamy and golden hues of ripening corn,-colours which at once contain the greatest amount of luminousness, and convey it with the greatest softness to the eye. The orange and the red rays, which are the least refrangible, can struggle through the air when all the other rays are flung off or tilted up, and are able even to make a horizontal passage, in all their brilliance, from the face of the setting sun, among the dense atmospheric strata immediately incumbent on sea and land. Hence the gorgeous glories of a calm and clear sunset,-the magnificence of the evening "clouds which cradle near the sun,”—the masses of visible burnished vapour which refract the beams that fall on them, and float the while in the flood of the unbroken beams, like islands of gold in a sea of molten silver. Then "Is the last sweet smile of the evening sun; How bright, how sublime its beaming! The rainbow, "the airy child of vapour and the sun," consists of many millions of minute spectrums arranged in the circumference of a circle. It is formed only on a falling shower, when the sun is more than half-way down the sky, and is seen only by spectators situated between it and the sun. The rain-drops act as prisms, each one dispersing a pencil of sunlight into a spectrum; the background of dark cloud acts as a screen to receive the spectrums, and to reflect them back on spectators; and every eye which beholds the bow is in a direct line between the sun and the summit of the arch, so that each spectator sees a different set of spectrums from another, and sees them so aggregated on the curve of the sphere, as to form part of a circle. "Where rests that arch? How stands its form so true Upon the darkening, gleaming, changing sky It rests upon thine own enchanted view, Its central point thine own admiring eye. The falling crystals in the showery air Transmit the colours of the riven rays, Around the charm'd ten thousand eyes that gaze." When only bits of shower are before the spectator, only bits of bow are beheld; and when an entire shower of sufficient breadth and height is seen from a very elevated position, almost an entire circle of bow is beheld. A secondary bow sometimes forms exteriorly to the primary one, larger, fainter, and spanning the same centre, but always exhibiting the colours in the reverse order. The rainbow charms all eyes, and adorns all landscapes, yet is supereminently beautiful, and surpassingly glorious, in a region of abruptly and stupendously tumulated surface. Any devout person who sees it over a snow-peak of the Alps, can scarcely fail to think of "the last rainbow o'er the skies-the emerald rainbow round the throne of God;" and perhaps all Christian voyagers who have beheld it amid the soaring volcanic isles of the Pacific Ocean, or on the mural mountains of the Norwegian sea-fiords, or at any similar blendings of the sublimities of cliff and ocean, may say, with Messrs Tyerman and Bennet-"The ground being heaved into enormous mountains, with steep and narrow dells between, the sun is continually faced by superb eminences on which 'the weary clouds oft labouring rest;' and showers fall many times in a day, accompanied by brilliant segments of the glorious arch which, under certain happy circumstances, may be seen bestriding the island itself from sea to sea, or resting one foot upon the sea, and the other on the earth, like the angel in the Apocalypse, who was himself' clothed with a cloud, and had a rainbow over his head."" The rainbow, of course, existed as well before the general flood as after. It had ever been observed as "the bow in the clouds," and could never have failed to enrapture the antediluvians as the most gorgeous appearance in the heavens, and was no doubt identified in the minds of Noah's family with the onfall of rain, and probably had been seen vividly and long on the water-bursts which first descended at the judicial opening of "the windows of heaven." It was, therefore, with pre-eminent fitness, and with utmost pathos of appeal, "set" or appointed as the token of God's covenant with them, that he would never again overwhelm them in a flood. It stood like a bridge of glory connecting the world which had been destroyed with the world which still existed; and the message of the divine mercy, when coming down to proclaim hope to all future ages, appropriately "lighted in mid ether on its brilliant arch." And now, in its moral meaning to all generations, as truly as in its physical cause, it is a mingling of "rays from heaven with tears from earth." "Such is the rainbow with its thousand dyes, Majestic token of its Maker's might, Pure zone of grace, grand coronal of light, God's own blest hand-mark, mystic, full, sublime, E Rainbows of faint colour and imperfect development, and rainbows with the green colour awanting, or with the yellow and the blue scarcely perceptible, occur under deficient conditions of light or of refraction. Arches of unrefracted light, or what might be called white rainbows, have been seen, but are very uncommon. Rainbows at night, formed by the light of the moon, are exactly similar to rainbows in the day, but whitish, and less bright. Mist-bows appear on fogs. Sea-bows are frequent on the spray of waves, and are distinct and vivid, and usually occur many together, but have their convexity downward, and their ends upward, and are very brief and vanishing. Grass-bows abound on the morning dew of pastures, and flit onwards before an advancing spectator, and present their convex part to the eye, and have different curves according to the height of the sun, but are necessarily all very tiny and toyish. Spray-bows, as brilliant as the bow in the heavens, and always popularly called rainbows, overarch the fall of many cascades and cataracts, and constitute a very striking feature of their scenic power. The bow of the Alpbach waterfall, near Meyringen, is one of peculiar beauty— triple, and very bright; the innermost iris almost a complete circle, and the two others more or less full according to the volume of the waters. The sun, and the moon, and sometimes also clouds and fogs, are liable to make very extraordinary appearances in unusual refractions or diffraction of light. When the air is charged with dry exhalations, the sun sometimes looks as red as blood. When it is loaded with vapour, in a state approaching that of thin fog, he appears shorn of his beams, but presents a white |