across Indian Ocean. Let us consider the course of the seasons in Ceylon, and correlate them with changes of pressure over India. In the month of February we find a very shallow stationary depression-not a cyclone-over Lower Bengal, a belt of high pressure stretching across the Bay of Bengal from Madras to Rangoon, and a general diminution of pressure from that belt to the equator. From this we might reasonably expect what we find— light south-west wind over Lower Bengal, variable breezes over Madras, and a light north-east monsoon Ceylon; but it is not so obvious why the south-west wind should be so fine and dry as it is. The low pressure over Bengal gets gradually more pronounced, and spreads with its accompanying south-west wind slowly southwards, till Ceylon is embraced within its sphere. These conditions are most pronounced towards the end of May, and we get the dry, nearly cloudless, hot season of India and Ceylon with a light south-west wind. Then the sky begins to cloud over, and suddenly rain bursts in a series of terrific thunderstorms, and the bad wet weather continues for two or three months. The rain begins in Ceylon, and then works slowly up the west coasts of India and Burmah -omitting Madras-till Calcutta and Lower Bengal are reached, three or four weeks later than Colombo. Then we are met by the strange fact that this, the most striking weather-change in the whole year, is associated by no change in the shape of the isobars. We give in our chapter on Weather Types two diagrams (Figs. 82 and 83) of Indian isobars just after the monsoon has burst over Bombay and Calcutta. The only difference in the isobars then and a fortnight previously, when the hot dry season prevailed, is that the level of pressure is a little lower, that the position of lowest barometer has moved a little higher up the Ganges, and that the distortion of the isobars by secondaries is more pronounced. When the monsoon is fairly established, we can, no doubt, see certain slight fluctuations in the shape and intensity of the isobars which accompany what is called "a break in the rains," and sometimes exceptionally heavy rain falls during the passage of a small cyclone from the Bay of Bengal up country; but we cannot find any change in the isobars to account for the sudden change of weather which is called in common parlance, "the burst of the monsoon." The quality of the rain, if nothing else, distinguishes the monsoon from cyclonic precipitation. The rain in front of a Bengal cyclone seems to grow out of the air, while that of the monsoon falls in thunderstorms and from heavy cumuloform clouds. The only rational suggestion which has been made to account for this burst of rain, would look to a sudden inrush of damp air from the region of the doldrums as the source of the change in weather, but not of the direction of the wind, or of the shape of the isobars; for the burst is apparently almost coincident with the disappearance of the belt of high pressure to the south of the Bay of Bengal.' No satisfactory clue has, however, yet been discovered either to the cause, or still less to the quantity, of nonisobaric rainfalls. They are the bugbear of every European forecaster, though in Japan, curiously enough, they find rain easier to announce than the direction of the wind. Mr. Finley, of the United States Signal Office, has made some very interesting studies on local rains that do not show on the isobaric charts. He takes a map of the United States, and puts in all the wind-arrows without any isobars. Very often he finds some large areas swept by a generally southerly wind, and others by a generally northerly wind, and he draws lines to mark out the tracts of country where these currents meet, and where they diverge. Then he finds that there are always local rains over the first areas, and rarely any over the latter. This would undoubtedly point to local vertical whirls between the meeting currents as the source of rain. Whether this is universally the case, or whether the conditions of all rains could be analyzed into small V's or secondaries if the isobars were constructed from stations sufficiently close together, we cannot at present say. The important thing is not to mix up all kinds of rain together when we want to discuss general meteorological problems. CHAPTER IX. PAMPEROS, WHIRLWINDS, AND TORNADOES. We will now describe two remarkable kinds of storms which occur in La Plata and in the United States respectively. PAMPEROS. The word "pampero" is, unfortunately, used in a very vague manner in the Argentine Republic and neighbouring states. Every south-west wind which blows from off the pampas is sometimes called a pampero; and there is a still further confusion caused by calling certain dry dust-storms pamperos sucios, or dry pamperos. The true pampero may be described as a south-west wind, ushered in by a sudden short squall, usually accompanied by rain and thunder, with a very peculiar form of cloud-wreath. We will describe these as given by D. Christison in the Proceedings of the Scottish Meteorological Society, No. lx. p. 330, and then we shall have no difficulty in recognizing a line-squall as the source of the pampero. The barometer always falls pretty steadily for from two to four days before the pampero, and always rises for some days after the squall. There are not enough barometric observations to allow of any generalizations as to the precise position of the squall relative to the trough of the general depression, but in two recorded cases the mercury began to rise some hours before the storm burst. Temperature is always very high before the squall, and then the sudden change of wind sends the thermometer rapidly down, sometimes as much as 33° in six hours. Thunder accompanies about three out of four pamperos ; but more or less rain always falls, except in the rarest cases. The wind before this class of pampero almost invariably blows moderately or gently for some days from easterly points, and then with a sudden burst the southwest wind comes down with its full strength, and, after blowing thus from ten to thirty minutes, either ceases entirely or continues with diminished force for a certain number of hours. In all cases but one the upper windcurrents have been seen to come from the north-west both before, during, and after the pampero. The general appearance of a pampero will be best understood by a description of an actual squall. “In the early morning of a day in November, the wind blew rather strongly from the north-east. The sky was cloudy, but not overcast, save in the south-west horizon. The clouds were moving very slowly from the west, or a little south of it, throwing out long streamers eastwards. About 8 a.m. the threatening masses in the south-west |