and provide against the danger. The Spaniards designate the violent and perilous snow-storms of the Andes, temporales, from their short duration.

419. Variable or erratic winds of temperate regions. Excepting the winds which blow about the equinoxes, and termed Equinoxial gales, the winds of extra-tropical regions are variable, blowing at no stated period, and from no fixed direction. From the records of the Royal Society we find that in Britain, the prevailing winds in the course of a year are as follows:-S. W. blows during 112 days; N. E. =58; W.=53; N. W. 50; S. E. = 32; E. = 26; S. = 18; and N. = 16 days. In Scotland, according to Dr Meek,' during seven years' observation, the average is as follows:-S. W.-174 days; N.E. = 104; S.E.47; and N. W=40 days. In Ireland the prevailing winds are the W. and S. W. We thus find that the most constant winds in Great Britain are the S. W. and N. E., and the same holds true over Europe,-Russia excepted, and in America. As we advance into the European Continent, Schouw observes that the increased ratio of westerly over easterly winds diminishes. Although these winds appear to be the effect of capricious causes, we cannot but think that they follow laws not yet fully developed. From April to May the northerly and easterly winds are frequent, arising from the current which flows southwards to replace the heated air over the Atlantic ocean, warmed by the solar rays as that luminary approaches to the summer solstice. In summer and autumn the opposite winds prevail, and the atmosphere is more moist and warm, because the balance of temperatures being now in favour of the land, the winds blow from the ocean. As the year advances, the winds first noticed again predominate, but they are accompanied by greater humidity than in the spring. It has already been observed, that the trade-winds give rise to an ascending current near the equator, and determine a westerly wind in the higher regions of the atmosphere, which descends about N. lat. 30°, (vide 380), and causes the predominance of S. W.

1 Stat. Acc. of Seot. vol. v.

* Beiträge zur vergleichenden Klimatologie.

winds. By the excess of these S. W. and N. E. winds, Professor Dove explains the production of the other variable winds of temperate regions. If we notice opposing currents upon a sheet of water, we will observe at the meeting of these currents, at one time a circular motion, at another perfect quiescence. Dove considers that whirlwinds of variable diameters and intensity arise in the region between those winds which are steadily blowing, and give rise to the phenomena in question, when the diameter is small, we shall have the whirlwind properly so called, when larger, the tornado, or the hurricane, or the winds of temperate regions, in proportion as the circle is increased in radius.

420. Professor Forbes of Edinburgh, in his Report on Meteorology to the British Association in 1840, states what Dove has observed, that when the wind changes it generally does so from the right to the left of the windrose, or in the direc tion of the handles of a watch. In the southern hemisphere there is an exception to this law; hence on the west of the windrose the warm wind is followed by a colder, the reverse of what is observed upon the eastern side of the card.

421. The law of storms, or the circular and parabolic direction which they generally follow, has been ably investigated by Reid, Redfield, Espy, Capper, Dove, and others, and determined beyond the shadow of doubt.' We have already several times referred to it. In its practical bearing it is of the greatest importance. The usual course of the wind in its veerings has been already noticed, viz.-from the E. to W. by S. in the northern hemisphere; and from E. to W. by N. to the south of the equator; but there are exceptions to this rule. However, when a vessel is met by a tempest blowing from the S.E. changing to S. and W., she should be steered to the S.E., which is the region S.E. of the violent storm; on the contrary, when the wind blows strong from the N.E.

See Redfield and Reid on Storms in Jameson's Jour. vol. xx. xxv.; Capper on prevailing storms of Atlantic Coast of N. America, in the same Journal, vol. xviii. ; Silliman's Jour.; Espy,-Philos. of Storms; Dove,-Pog. Annalen, 1841, tom. lii; Athen. No. 565.-Reid; Ib. No. 676,-Epsy; Thom,-Inquiry into Nature and Cause of Storms in Indian Ocean; Piddington,-Horn-book of Storms, Calcutta 1844, &c.

veering to N. and N.W., she should be directed N.W.,-these indications being good in the temperate zone of the northern hemisphere. Again, if in the same hemisphere, and within the torrid zone, the wind blows from N.E., E., and S.E. the vessel must be guided to the N.E.; but if it blows from the N.W. veering by W. to S.W., then she should steer S.W. In the southern hemisphere the following are the indications:if within the tropics, the wind blows violently from S.E., turning to S. and S. W., steer N.W.; but if it blows from E. to N., and N.W., steer S.E. In the southern temperate zone, if the wind is N.E., then N., and N.W., sail N.E.; if S.E., S., and S.W., the vessel must be steered S.W.,-the object in all these movements being to sail out of the storm.

422. Temperature of variable winds. Although the erratic winds of extra-tropical climates have their temperatures modified by physical circumstances, leading to anomalies and local differences, still the results of meteorological observations exhibit some very interesting constances. The coldest of all winds, with scarcely an exception, is the N.N.E., while that one diametrically opposite is the warmest. The mean temperatures of the eight leading winds, according to M. Otto Eisenlohr, are as follows:

423. Of the effects of variable winds upon health it is not the design of the present volume to treat, but who has not experienced the inconvenience arising from easterly blasts ? The whole creation suffers from its malign influence. We need not ask the gouty or rheumatic of their agonies, the neuralgic of their pangs, nor the hypochondriac of their suf

ferings; to the consumptive it blows destructively. How different are our feelings under the genial breath of the opposite wind, and its neighbours on the western side of the windrose. The south may bring moisture, and the north whiten the ground, but though the latter is cold, it is bracing, and neither, is absolutely disagreeable. The east wind and its companions are the unwelcome visitors,-and why is it so?

CHAPTER XVIII.

Prognostications. 424. Annus Magnus. 425. Prognostications in Eastern climes. 426. In our own climate; from the Barometer. 427. From the Sun. 428. From the Moon. 429. From the Stars. 430. From Twilight. 431. From the Looming. 432. From the Rainbow. 433. From Clouds. 434. From Mists. 435. From Winds. 436. From the Vegetable kingdom. 437. From the Animal kingdom. 438. Anecdote of the spider. 439. From Inanimate bodies. 440. Opinion of Arago and Sir David Brewster. Conclusion.

Πάσας τὰς ἡμέρας τῆς γῆς, σπέρμα και θερισμός, ψύχος καὶ καῦμα, θέροςκαὶ ἔας, ἡμέραν καὶ νύκτα οὐ καταπαύσουσι.—ΓΕΝ. ή. 22.

"The seasons are regular enough to authorise expectation, while their irregularity induces, on the part of the cultivator of the soil, a necessity for activity, vigilance, and precaution."

424. It was a favourite opinion with the ancients, that events followed in sequential series—hence arose the platonic year, or annus magnus. This was a period of 25,868 years,' during which the equinoxes complete the series of retrogressions, in other words, when the equatorial and ecliptic axes of the earth being ideally prolonged, the pole of the former shall have revolved round the other. Then, the world, in their opi

This period has been variously estimated. We give the cycle as determined by Sir John Herschel,-Astron. p. 169. Tycho Brahe assigned the length at 25,816 years; Cassini, at 24,800; and Ricciolus, at 25,910. The ancients extended the period far beyond six-and-twenty thousand years, even to that of 300,000. Cassander lengthened it to 360,000 years; and according to Orpheus, it was 120,000 years. See Prichard,-Egypt. Mythol. p. 182; Censorinus,-De Die Natali, &c.