with the exception of the tornado of Natchez, in the State of Mississippi (May 7, 1840), the tornados described by Mr. Loomis only caused on an average the death of one person. At Natchez extraordinary circumstances took place, for by far the greater number of the 317 victims of the catastrophe were drowned in the river, where the tornado sunk in a few seconds two steamers and sixty flat-bottomed boats. Altogether this tornado seems to have been one of extraordinary fury. Nearly nine inches of rain fell, along with enormously large hail-stones. Trap doors and a desk fastened with three locks were torn open as by an explosion. A tin plate and a window were carried to distances of twenty and thirty miles. The spout of Calcutta (April 8, 1838), which on its march of sixteen miles killed no less than 215 persons, wounded 233, and destroyed at the same time 1,245 Indian huts, must therefore be considered as much more disastrous than any of the American tornados. The chief cause of its dreadful effects seems to have been its very slow progress, so that its local duration amounted to from four to seven minutes, while in the American tornados it rarely surpasses a minute. The rapidity of the wind within this spout was so enormous that a bamboo cane was driven through a mud wall five feet thick and clothed on both sides with brick. A six-pounder, says the editor of the India Review,' could hardly have produced a greater effect. CHAPTER IX. FOGS. Evaporation-Point of Saturation of the Air with Moisture-The Formation of Fogs-London Fogs-Lines by Archdeacon Butler-Effect of a London Fog (Dec. 1873) on Horned Cattle-John Evelyn's Description of a London FogDense Fogs over the Barks of Newfoundland-In Behring's Sea-Fogs produced by the Arctic Icefields and Icebergs-Fogs on the Peruvian Coast-Number of Foggy Days in various parts of Europe--Fogs in the Alps-Picturesque Effects of Fog-Day Fogs-The Höhrauch-The dry North American Fog-The Caliña-Obscuration of the Atmosphere by Volcanic Eruptions-Extraordinary Dry Fcgs of the Years 526, 1783, and 1830 attributed to Nebulous Planetary Matter-Blueness of the Sun observed in Various PlacesA Lesson of Humility. THE THE ocean is the source of all life on earth-the colossal reservoir which provides all animated nature with the Without the sea, all land water necessary for its existence. would be a naked waste- -a dreadful desert of sand and rock. It is the ocean which fills our granaries, adorns our gardens, feeds our flocks, and spreads the green canopy of our forests. It scatters fruits without number over the earth, for the nourishment of unnumbered creatures; if its urns were to be exhausted, death alone would reign on earth, and one common grave devour all living things. The sun has had his worshippers among the people of ancient days; but the sea was equally deserving of pagan homage, for without the sea, no human eye would have been dazzled by the great luminary's light. The warmth of the sun is indeed a prime necessity of life; but warmth requires the co-operation of moisture to awaken and maintain life, and this moisture is derived from the inexhaustible stores of the sea. The sun and the ocean, however, are still in need of a third auxiliary to enable them to scatter plenty over the smiling land; in vain would the sun dart forth his enlivening beams, in vain the ocean be filled with floods without end, if the atmosphere were not ready to absorb the exhalations of the sea, and to convey them on the wings of the wind far into the interior of the continents. Thus, every raindrop that irrigates our fields, every mist that obscures the air, is the product of the grand and harmonious action of the sun, the sea, and the atmosphere. The evaporation of water is a phenomenon which must strike even the most careless observer. Everywhere the humidity of winter disappears from the ground after a few days of warm and serene weather. The stones moistened by a summer shower, the plants dripping with morning dew, are dried up after a few hours of sunshine. The evaporation of water into the air is confined entirely to the surface, and hence it is always proportional to the surface exposed to the action of the air. Accordingly, observation shows that in maritime countries, and in marshy situations, in the neighbourhood of lakes, rivers, and over the surface of the sea, the evaporation is much greater than in inland countries and dry situations. It is found that evaporation is greatest in hot weather; whence it must depend, in some degree, upon the temperature of the air. There are, however, several circumstances which affect the quantity of vapour rising from water, even at the same temperature. Thus, we find that evaporation is least in calm weather, increases when there is wind, and is greater in proportion as the wind is stronger. The air, however, can only contain a certain quantity of aqueous vapour, which is constantly varying with its temperature. When its warmth increases, its capacity of retaining moisture in the invisible form of aqueous vapour increases; when there is a decrease of its temperature we find a proportional decrease in the quantity of aqueous vapour which it is able to retain. The point of extreme atmospherical moisture is, therefore, as fluctuating as the capricious winds, or as the rise and fall of the barometer. In winter (and that is generally the case) the air, though containing but a comparatively small quantity of aqueous vapour, may thus be apparently more moist or nearer its point of saturation than in summer, when it is laden with a far greater quantity of invisible water. Evaporation may, in the latter case, be still proceeding with great activity, while in the former it is nearly reduced to a standstill. In the months of November and December the air seems generally more damp than in July, when it actually contains more than double the quantity of water. Over the surface of the ocean the air is generally at all seasons and in every latitude near its point of saturation. On land the degree of its moisture depends chiefly upon the nature of the soil, the seasons, the direction of the wind, the distance of the sea, and the height above its level. When the temperature of a warmer stratum of air is so far cooled that the quantity of aqueous vapour it contains exceeds its actual point of saturation, this excess of moisture condenses, and either assumes the form of dew, or becomes visible to the eye in the form of a fog or cloud. Fogs chiefly form over seas, lakes, rivers, and damp countries, particularly in autumn, when the ground is still comparatively warm, and the contiguous air strata, which are saturated with moisture, ascend into a colder atmosphere. On damp meadows, wreaths of fog are frequently seen to arise after sunset, even in the hottest months; but its formation is generally more abundant towards morning. In winter the rivers smoke because the air which is in contact with the warmer water acquires a higher temperature than that of the superjacent strata, and parts on rising with the vapours it had absorbed. Fogs may also be caused by a colder air current descending upon a sheet of water or damp ground, and mixing with the warmer and moister atmosphere above it. In countries where the air is generally damp, and subject to frequent and rapid changes of temperature, fogs are of frequent occurrence; as, for instance, on the coasts of north-western Europe, which faces the moist breezes of the Atlantic. The fogs of London, which, from their density and the intermingled particles of smoke, acquire a peculiarly dull, funereal tinge, have long enjoyed a proverbial celebrity. Not a year passes over the great metropolis without some days of intense fog, whose dark Cimmerian gloom is well expressed in the following lines: Darkness upon the land! midnight at noon! Hid was the sun, the stars refused their light, And Egypt's noontide blaze was quenched in night. Written by ARCHDEACON BUTLER during an intense London fog From December 8 to 14, 1873, London was enveloped in a misty shroud of almost unprecedented density, which entirely stopped the traffic on the river and the business in the docks. On the 12th about noon, the black veil cleared up a little, so that objects could be indistinctly seen at a few paces distance; but towards evening thick fog clouds rose again from the marshes of the Thames, so that no gas-lights could be distinguished in the streets, and the few cabs and omnibuses which ventured out had to be escorted by torchbearers, and could only move step by step. The fog-signals exploding without intermission at the railway stations, and the dismal shrieks of the fog-horn, served to render the gloom still more melancholy. Many lives were lost; at Wapping, two men walked into the river down the boat-stairs and were drowned. A similar fate befel two respectable artizans, who, on returning from their work to St. John's Wood, walked into the Regent's Canal. Fifteen persons are said. to have perished in the docks on the north side of the river alone. The losses sustained by the interruption of all traffic were immense. A phenomenon like this, enveloping a huge metropolis in obscurity, is, indeed, a grievous calamity, more full of anxiety and care, entailing more disasters, and causing a greater loss of life, than the most violent thunderstorm. The fog, laden with the smoke of half a million of chimneys, and the countless effluvia of a town embracing a population of more than three millions, had a very curious and terrible effect upon the horned cattle at the Islington show, which, accustomed to a purer air, were unable to breathe in the |
