that observed in front of a cyclone which is adv a direction perpendicular to the coast line. A Typhoons which strike the coast of China, and it from the SW., the point where they change th must be on the continent, and their subsequent in the temperate zone could be only traced in the Seas. These Typhoons are frequently accompanie tensive inundations of the coasts by the sea, c Macgowan's work* contains numerous instance from Chinese sources. In the year 1748, 20,000 were destroyed by an inundation of the sea d storm of this character. The violence which thes exhibit even on the eastern edge of the Monsoon apparent from the fact, that in one storm which pas the island Guaru, one of the Ladrone Islands, in Sep 1855, more than 8,000 people were rendered hou the space of twenty minutes by the fall of their ro

It is moreover evident that the connection bet storm in the temperate zone, and the original cyc the torrid zone, to which it owes its origin, n necessarily be traceable, as a continuously adv minimum, in the lower strata of the atmosphere. W explained above (p. 36) the circumstance that the minant winds in the upper strata, between the topi SW., so that the identical conditions are from th first presented to the upper part of the cyclone, whic not be experienced by the lower part before it leav zone of the Trade-winds. Hence the upper portic dilate at once, and advance in a direction differ that in which the lower portion moves. A very proof of this connection, which was pointed out b in the year 1842, is given by the hurricane at the Havannah on October 12, 1846, in which case the effect of the diminution of pressure has been already

The tempest at La Verpellière, between Lyons and Grenoble, came over the chain of hills in the Ardeche district with a NW. wind. At the same time, from seven o'clock on the morning of October 17, the sky became extraordinarily overcast over Grenoble. The stifling blasts of a south-easterly sirocco were felt there; blood-coloured rain fell there, together with a reddish dust, which covered the diligences near Lyons to the depth of one or two lines. This occurred, according to Dupasquier, during a calm, or while the wind was from the S., and very light. The rain was not excessive; but the appearance of the sky was terrific. Two banks of clouds - one in the S., the other in the NW. - were the foci of the storm. The wind shifted from minute to minute; flashes of lightning of extraor

* The fall of the barometer, for each hour, if we count the time from the period at which the centre reached the town, is as follows (in inches) : Between 12 and 6 hours before, 0.077 | Between 4 and 2 hours before 0.290

6 3

0.103

2

0-397

-

:

dinary brightness crossed the sky, not vertically, but he flying round more than one-third part of the horizon. flash birds of passage on the wing redoubled their terror. In the streets, in open rooms, and in the chin inhabitants caught ducks, quails, fieldfares, nightin catchers, and other birds.

The fall of the barometer at the different st given in the following table :

Bordeaux, from 13th to 16th, 0-743 inches, and up to the 20th rose 0

According to Ehrenberg's microscopical analys is nothing either in the internal or the external cl of the dust which fell on that occasion which wOL him to attribute its origin to Africa. On the co many of the forms therein contained were, either or in a great degree, indigenous to South Ameri could not have come from the interior of a contine must have been carried from the sea-coast (if w assume that it all came from one district), inasmuc contained existing marine forms.*

This case which we have just described forms natural introduction to the consideration of the which arise outside the zone of the Trade-winds.

221

II.- Storms which arise at the exterior edge of the Zone of the Trade-winds.

In the preceding pages we have referred the West India hurricanes to the interference of lateral cross-currents with the upper Trade-wind on its return from the equator, portions of which, being forced to enter the lower strata of the atmosphere, meet with a constant wind, moving in a direction opposite to their own, and thus produce a cyclone. Outside the Trade-wind area the upper current descends to the surface of the earth, and is predominant there in different districts at different times, while the under-current in the opposite direction is not constant. Here, then, we shall find that the conditions of interference will constantly be presented, but the currents will be directly opposed to each other, so that they will only check each other's progress. In this case, a partial gyration indicates nothing more than that one of the currents has at last overcome the resistance of the other, a success which is just as liable to be reversed as not. In all such cases, the warm equatorial current will produce a considerable depression of the barometer, inasmuch as in its progress into colder regions it loses the moisture which it had brought with it, in repeated discharges of rain. This fall of the barometer will be observable along a line perpendicular to the direction of the current, rather than at the centre of a rotating mass of air. In the case of cyclones the height of the barometer increases in all directions from the centre; in the case now under consideration the

f

barometer will rise to a great height over an area, affected by the polar current, which has beer in its progress. This contrast of two distri respectively high and low levels of the barometer, be marked by great differences of temperature the regions in question.

The investigation of such phenomena require vations from a great number of stations scattered a as possible over an extensive area, In the consi of the preceding class of storms, we have derived formation principally from the logs of ships, but class we are referred, by the nature of the case, pri to observations made on land. In a larger work of I have described at length several instances of th ference of and strife between two opposite curr which I shall quote a few cases here.

THE CONFLICT OF OPPOSITE CURRENTS IN JANUAR

The month of November 1849 had been very throughout Germany, but at the end of the mo intense degree of cold, accompanied by easterly was felt in European Russia and the east of Ger This was broken for a short time, in the middle cember, by southerly and westerly winds; but to the end of the year it recommenced, and in Ja with easterly winds, reached a degree of intens eastern Germany such as had not been recorded at of the stations since the observations commenced Posen the thermometer fell to - 37°.7 Fahr.; at Bron

*

Darstellung der Wärme-Erscheinungen durch fünftägige Mittel ve bis 1855, mit besonderer Berücksichtigung strenger Winter (Represe of the Phenomena of Temperature by Five-Day means, from 1782 t with a Special Reference to Severe Winters). Berlin, 1856, folio, 11