tempest, waterspouts were seen at Naples. On the 25th July 1847, one fell about 1 P. M. at Morecambe Bay, near Milnthorpe. The column was curved to the south, and appeared horizontal about midway between the heavy thunder-cloud from which it descended and the sands; it lasted ten minutes, and was accompanied by vivid lightnings. On August 20. 1847, a similar meteor was seen on sailing from Erie, Pennsylvania, to Cleveland, Ohio. Upon the 31st of August 1848, a whirlwind occurred at Dover, and at the same time a waterspout was seen at Deal, on the east coast of Kent; on the same day at noon, a waterspout was seen at Woodbridge, which passed overland to Hollesley and Bawdsey, on the east coast of Suffolk, where there was a great fall of rain and ice; it burst in the river near Ramsholt.3 Peltier mentions 137 instances of this phenomenon, of which thirty-three occurred in calms, and ten appeared in a cloudless sky. cumstances. 188. The pillar of the waterspout consists of condensed vapour; it is often deep indigo-blue, and similar in tint to the superincumbent cloud. When the motions of the base and apex are equal and in the same direction, the meteor presents itself perpendicularly, but it inclines under different cirElectrical phenomena attend its presence, as are indicated by the lightning sometimes observed. It is generally after a storm or long-continued sultry weather, that the meteor appears. It occurs at sea, in straits, by rivers, and sometimes upon land. The discharged water is said to be always fresh, consequently not obtained directly from the ocean. 189. Franklin assigns to the waterspout an origin similar to that of the whirlwind-the rushing of a fluid from all sides to a common centre, producing a vertical motion of the particles on their line of meeting. Both phenomena are attributed to electric disturbances. It is true that electrical phenomena attend, but it remains to be proved whether they are not secondary effects. We are disposed to think, that while 1 Silliman's Amer. Jour. N. S. No. 12, 2 Record of 7th Sept. 1848. Traité des Trombes, 1840. p. 362. Ib. Bury Post. the meteor owes its presence to the agency of electricity, the lightning seen to issue from the column, is induced, by the new arrangement of the aqueous particles. The Count Xavier de Maistre succeeded in imitating the leading peculiarities of the waterspout by mechanical rotation of a fluid; and Peltier' artificially formed it, in all its parts, by means of electricity. Meikle assigns a different cause; premising that the ascending column arises from the meeting of currents as Franklin supposed, he explains the descending column by the condensation of aqueous vapour through "the cold due to the rarefaction which is occasioned both by the whirling motion of the air, and by its rapid ascent. The more swift the rotation, the greater obviously will be the rarefaction and cold; and of course the lower down in the axis or stem will the condensation of the moisture extend." In ascribing this meteor, as some have done, to a vacuum formed over the sea and the elevation of the water through atmospheric pressure, it must not be forgotten that, unaided by other means, pressure can raise the water no higher than about 32 feet. Traité des Trombes, 1840. 2 Ency. Brit. 7th ed. vol. xii. p. 135; see also Jones' Physiol. Disquis. p. 595; Johnson's Jour. from India to England in 1817, p. 6; Oerstedt,-Schumacher's Annuaire, 1838. CHAPTER IX. 190. Hail. 191. Sound previous to its fall. 192. During night. 193. Path of the hail-storm. 194. Theory of formation. 195. Conformation, figure. 196. Remarkable hail-storms. 197. Hail within the tropics. 198. Red hail; acid hail. 199. Snow; forms. 200. Colour, lightness. 201. Chemical peculiarities. 202. Electricity of snow. 203. Amount which falls in different countries. 204. The avalanche. 205. Catastrophe in the Val de Bagnes. 206. Kinds of avalanches. 207. Avalanches of Mont Blanc. 208. Dangers; Dr Hamel. 209. Described by Talfourd; Simond. 210. Casualties. 211. Wind of the avalanche. 212. Eboulement. 213. Utility of snow. 214. Red and green snow. 215. Met with in Europe. 216. Snow-mould. 217. Sleet. 218. The glacier. 219. Magnitude. 220. Dangers. 221. Regular motion of the glacier. 222. Unexpected movements. 223. Crevasses. 224. Forbes' observations on their progression. 225. Destruction; formation. 226. Theory of their motion; gravitation theory of Saussure. 227. Dilatation theory of Agassiz and Charpentier. 228. Viscous theory of Forbes; internal structure. 229. Resemblance to a river. 230. Inclination. 231. Colour. 231. Wind of the glacier. 233. Moraines. 234. Glacier tables. 235. Glacier springs. 236. The icebergs; magnitude. 237. Where not met with. 238. Liable to sudden fracture. 230. Mist-cap of the iceberg. 240. Physical properties of ice. "Ye icy-falls! ye that from the mountain's brow Who made you glorious as the gates of heaven God! sing, ye meadow streams, with gladsome voice! COLERIDGE. 190. Hail differs from rain in temperature and from snow in the aggregation of its particles. It depends upon the coexistence of sudden and intense cold in a humid atmosphere. The nimbus may be seen approaching, with a snow-like band in the horizon, forming a striking contrast of white and darkgrey approaching to black, with an azure sky; a sense of cold accompanies the rustling wind, a peculiar sound perchance is heard, and hailstones descend, dancing on the ground like pith-balls excited by electricity. 191. The fall of hail is often preceded or accompanied by a loud and peculiar noise. It is long since this was observed. Kalm noticed it on the 30th of April 1744 at Moscow; and Tessier, on the 13th of July 1788 in France. It has been compared by Peltier, who has heard it in the Department of La Somme, to the galloping of horsemen, or it resembles the pouring of shot from one vessel to another. It has been explained by the striking of the hailstones against each other, either by the force of their gravity and the wind, or, as Volta's theory of their formation implies, by their alternate attraction and repulsion between the strata of clouds oppositely electrified. May it not arise in part from the rapidity of its descent through the atmosphere, and the resistance presented to its fall? 192. This meteor rarely appears during the night, though Kämtz records several instances. Hail-storms most frequently occur at the hottest period of the day. In this country they are most abundant in winter; the relative proportions being, in In Germany and Switzerland the proportions are somewhat different, as Kämtz has shown from the records of the Meteorological Society of the Palatinate, where the seasons and hours of 440 hail-storms are noted. From that table we find that 194 occurred in spring, 122 in summer, 66 in autumn, and 58 in winter. During the same seasons, the numbers were greatest at 2 P. M., viz.-83, 15, 13, and 10; from 10 P. M. to Lehrbuch der Meteorologie. 2 Vorlesung über Met.; Ephemerides Soc. Met. Palatine, Mannheim. 4 A. M. both inclusive, we find only 18 hail-storms tabulated, of which, 8 occurred in summer, 5 in winter, 3 in autumn and 2 in spring. That hail falls among the lofty Alps, and even, as Balmat found, on the summit of Mont Blanc, is satisfactorily testified. 193. The path of the hail-storm is generally narrow, resembling in some respects that of the tornado. This was well observed in the storm of April 1697, which passed over the north-west of England; and more recently in that of the Orkney Islands of the 24th of July 1818, the length of which from S.W. to N.E. was twenty miles, and breadth about oneand-a-half. This storm advanced at the rate of about a mile in ninety seconds, not enduring more than nine minutes at any one place, though ice fell nine inches deep: the barometer descended 1.15 in. Tessier mentions one, on the 13th July 1788, which was propgaated directly from the S.W. of France to Utrecht; it moved in a double column from S.W. to N.E., with an intervening distance of about twelve miles, where and on either side it rained. The breadth of the column to the west, was nearly ten miles, while that to the east, was five; the one extended very nearly 500, and the other 440 miles. The eastern column passed over Artenay near Orleans at 7.5 A. M.; Andouville in La Beauce, at 8; the environs of Paris, at 8.5; Crespy in Valois, about 9.5; Cateau-Cambresis, at 11; and reached Utrecht at 2.5 P.M. The western column appeared at La Rochelle after a tempestuous night, and crossed not far from Loches at 6.5 A.M.; it passed near to Chartres, at 7.5; Rambouillet, at 8; Pontoise, at 8.5; Douai, at 11; Courtrai, at 12.5; and Flessingue about 1.5 P.M. At each of these places its violence continued only a few minutes, but the execution was most disastrous; property valued at 24,962,000 francs was lost."' 194. The descent of hail during thunder-storms, and from an atmosphere highly charged with electricity, led Count Volta and others to assign to it an electric origin; according to which hypothesis, the following conditions are required :--a dry atmosphere above the cloud; speedy evaporation under 1 Mém. de l'Acad. des Sc. tom. xc.; Epsy on Storms, p. xx. |