TO THE RAINBOW. TRIUMPHAL arch! that fills the sky To teach me what thou art. Still seem as to my childhood's sight, For happy spirits to alight Betwixt the earth and heaven. Can all that optics teach, unfold Thy form to please me so, As when I dreamt of gems and gold Hid in thy radiant bow !-CAMPBELL. LOCAL STORM.-When Mr. Scoresby, sen., commanded the ship Henrietta, he, on one oceasion, experienced on the Greenland Sea a tedious gale, accompanied by snowy weather. As the wind began to abate, a ship came up under all sails. The master hailed the Henrietta, and inquired why she was under close-reefed top-sails in such moderate weather. On being told that a storm had just subsided, he declared that he knew nothing of it, though he had observed a swell and a black cloud a-head of his ship, that seemed to advance before him, until he was overshadowed by it, a little while before he had come up with the Henrietta. He had had fine weather and light winds the whole day, INVOCATION TO RAIN. [From the German.] DESCEND, descend, O shower! Thy liquid treasures o'er the meadows pour, And raise each drooping flower. Yon trees that late, in blooming pride, Thy moistening aid implore; Yon bower, round which the woodbine gay, Oh, let not then the woodbine fade, To every plant thy care extend, And haste, in plenteous streams descend, O balmy shower! Yon herds that deck the mountain's brow, And those that range the plain below, Enfeebled by the noontide ray, Oh, let not nature plead in vain, Let not the flower that decks the plain In vain thy aid implore; But haste, thy pearly treasures bring, And soft descend, O shower! While Health, by smiling Plenty crowned, And hail thy genial power. UTILITY OF STORMS.-Dr. Huxam, in reference to epidemic diseases, remarks, that he often saw them abate greatly, both in their number and violence, after stormy and heavy rains, the contagious effluvia, and morbid congestions of the atmosphere being thus dispersed. In this way, he continues, even tempests themselves very frequently prove salutary, stagnant air, no less than stagnant water, being liable to corruption, unless often put in motion. The salubrity occasioned by the agitation of the air, which is more general, perhaps, on the sea-coast than in any other situation, was noticed with great interest by the ancients. Augustus Cæsar was so strongly impressed with its beneficial influence, that he built and dedicated a temple to Circius, a wind so powerful that it frequently blew down the houses of the people. The inhabitants of Gaul also, as Seneca informs us, gave public thanks to this exceedingly tempestuous wind, in consequence of its clearing the atmosphere and rendering it healthful. JANUARY. Now the sullen whirlwinds ring; Forests groan beneath his feet, Round him sweeps the bitter sleet Like a giant spectre's pall; But a kingly coronal, Where ten thousand star-beams glow, Flashes round his frowning brow. Dead beneath the naked tree Lies the bird, and lies the bee; Bound, in fetters chill and strong, Frozen, hueless, loveless, dumb! METHOD OF ASCERTAINING THE PURITY OF WATER.-The purity of water is indicated by its specific gravity. By a late act of parliament it is defined that a cubic inch of water purified by distillation weighs, at the temperature of 62 deg., barometer 30 inches, exactly 252-458 grains. An imperial pint of perfectly pure water weighs precisely 20 avoirdupois ounces at 62 degrees. Any water heavier than this must be less pure. That the lightest water is the best is an old and true principle. Pliny says that some judge of the wholesomeness of waters by contrasting their weights. Celsus alludes to the same practice," nam levis pondere apparet.' Hippocrates thought that the best water is that which heats and cools in the shortest time; and his echo and expositor, Celsus, affirms the same thing. Hoffman informs us that rivers of a rapid current, or which fall down mountains, afford a purer water than those that are more slow; and hence, he says, that ships coming out of the river Maine into the Rhine draw more water, and sink deeper in the latter, because the waters of the Rhine fall from the highest mountains of the Grisons country. PROGNOSTICS DRAWN FROM TERRESTRIAL BODIES.-1st. If the flame of the lamp sparkles, or if it forms an excrescence, there will be, in that case, a strong probability of rain.-2d. The same happens when the soot loosens and falls down the chimneys.-3rd. If the coals in the grate blaze more than usual, or flame with more activity, it is a sign of wind.-4th. On the contrary, when the flame is steady and uniform, it is a sign of fine weather.-5th. If the sound of the bells is heard from afar, it is a sign of wind, or a change of weather.-6th. If pleasant or offensive smells are condensed, that is, become stronger, they are signs of rain.—7th. The frequent change of the wind is the forerunner of a violent storm. DEW.-The interesting phenomenon of dew was not at all understood until lately, since the laws of radiant heat have been investigated. At sun-rise, in particular states of the sky, every blade of grass and leaflet is found not wetted, as if by a shower, but studded with a row of distinct globules most transparent and beautiful, bending it down by their weight, and falling like pearls when the blade is shaken. These are formed in the course of the night by a gradual deposition on bodies, rendered by radiation colder than the air around them, of the moisture which rises invisibly from water surfaces into the air during the heat of the day. In a clear night the objects on the surface of the earth radiate heat upwards through the air, which impedes not, while there is nothing nearer than the stars to return the radiation: they, consequently, soon become colder, and if the air around has its usual load of moisture, part of this will be deposited on them, exactly as the invisible moisture in the air of a room is deposited on a cold bottle of wine when first brought from the cellar. Air itself seems not to lose heat by radiation. A thermometer placed upon the earth any time after sun-set until sun-rise next morning, generally stands considerably lower than another suspended in the air a few feet above it; owing to the radiation of the heat upwards from the earth, while the air remains nearly in the same state. During the day, while the sun shines, the earth is much warmer than the air. The reason why the dew falls, or forms so much more copiously upon the soft spongy surface of leaves and flowers, where it is wanted, than on the hard surface of stones and sand, where it would be of no use, is the difference of their radiating powers. There is no state of the atmosphere in which artificial dew may not be made to form on a body, by having it sufficiently cooled, and the degree of heat at which it first begins to appear, is called the dewpoint, and is an important particular in the meteorological report of the day. In cloudy nights heat is radiated back from the clouds, and the earth below not being so much cooled, the dew is scanty or deficient. On the contrary, when uninformed persons would least expect the dew, namely, in warm, very clear nights, and, perhaps, when the beautiful moon invites to walking, and music adds to its charm-as in some of the evenings of autumn with the harvest moon and harvest occupations-then is the dew more abundant, and the danger greater to delicate persons of taking harm by walking among the grass.-Dr. Arnott's Elements of Physics. NEW ACOUSTICAL EXPERIMENT.-If one of the branches of a vibrating tuning-fork be brought near the embouchure of a flute, the lateral apertures of which are stopped so as to render it capable of producing the same sound as the fork, then the feeble and scarcely audible sound of the fork will be augmented by the rich resonance of the column of air within the flute. The sound will be found greatly to decrease by closing or opening another aperture; for the alteration of the length of the column of air in such a case renders it no longer proper to reciprocate perfectly the sound of the fork. This experiment may be easily tried on a concert flute with a C tuning-fork. To ensure success, it is necessary to remark that when a flute is blown into with the mouth, the under lip partly covering the embouchure, renders the tone about a semitone flatter than the sound when the embouchure is entirely uncovered; and as the latter must be in unison to that of the tuning-forks, it is necessary, in most cases, to finger the flute for B when a C tuning-fork is employed. We are indebted to Mr. C. Weatstone for this discovery. CLOUDS AND SUNSHINE. LOWERING clouds obscure the sky, The burning sun oft nips the flower, When pleasure would possess the breast, When hope would lull the soul to rest, But love can smooth life's ruffled stream, From eyes we love, one cheering gleam FALL OF AEROLITES AND SHOWER OF FISHES.-Visiting all the chief cities of Anatolia, or Asia Minor, he at length came to Erzeroum. There the king inquired of him one day whether he had ever seen a stone that had fallen from heaven; he answered in the negative. "Such a stone,” continued the king, "has fallen in the environs of our city;" he then ordered some men to bring it in. It was a black, shining, and exceedingly hard substance, not yielding to the hammer, and weighing above a talent. This is not the only mention of the fall of aerolites which occurs in Arabian writers. They tell of a shower of stones which fell in the province of Africa Proper, and killed all who were beneath it. They also relate that a stone was one day brought to the Calif Motawekkel, which had fallen from the air in Tabaristan it weighed 840 roti (620 pounds avoirdupois); the noise it made in falling was heard at a distance of four parasangs in all directions, and it buried itself in the ground five cubits deep. Many other similar instances are mentioned by them; and the observations of modern philosophers leave no room to doubt the correctness of their accounts. But Jahedh relates a meteoric phenomenon of a much more extraordinary kind. At Aidhadj, a city between Ispahan and Kuzistan, as he narrates it, there was seen a dense black cloud, so close to the earth that it might be almost touched with the head; there issued from it noises like the cries of a male camel. The cloud at last broke, and there |