the southwest monsoon sets in on both coasts of the peninsula.

The relation of the winds to temperature, humidity, and barometric pressure is most carefully presented in detail. In a general summary he states that the northeast monsoon of the Indian seas is produced by the cooling and condensation of a comparatively calm atmosphere over the land surface of India. Its origin is in the plains of the Punjab, and Upper and Central India and Assam, probably also on the southern slopes of the Himalaya. These wind currents are fed by an upper current which he terms the anti-monsoon, of which he traces two distinct branches.

The double system of upper and lower currents is presented by him in admirably constructed charts, on which both are shown in their proper relations to each other. The southwest monsoon is produced by the heating of the land surface of the peninsula. As the heat increases the pressure falls steadily, and the sea winds are drawn from a greater distance south. At length, in general, the ridge of high pressure over the sea, which has been steadily receding southward since February, is obliterated, and the southeast trade, or perhaps only a portion of it, crossing the equator, brings the monsoon rains to Bengal and the western coast of India.Phil. Trans. Royal Soc. of London, CLXIV., 363.

ORIGIN OF CYCLONES.

The origin of the cyclones of the Bay of Bengal has been studied by Blanford, of Calcutta, who concludes that they are not necessarily produced by two parallel currents blowing in opposite directions, but rather that a calm state of atmosphere, or one in which the winds are light and variable over an open sea, is a condition favorable to the formation of these storms; and that a second condition is high or moderately high temperature. In consequence of this collocation, a large quantity of vapor is produced, ascends into the atmosphere and is condensed, with a liberation of its latent heat over the place of its production instead of being carried to some distant region. The atmospheric pressure is thus locally lowered, tending to cause an indraft of air. The formation of cyclones is, then, finally determined by an inrush of a saturated storm-current of air from the southwest or

west-southwest. This latter feature may possibly be one peculiar to the northwest portion of the Bay of Bengal; and Blanford especially guards himself against being supposed to extend these views to the case of any other area than that which he has especially dealt with.-Phil. Trans. Royal Soc. of London, CLXIV., 563.

DRY THUNDER-STORMS.

A correspondent in Oregon, Missouri, states: "When the earth has become dry, parched, and very warm, I have often, on the occasion of thunder-storms, noticed for hours, while it was thundering very hard, a mist falling from the storm-clouds, and roll back, after nearly reaching the earth, in the form of lighter vapor. I think this rain or mist in falling passed down to the stratum of very hot air on the earth's surface, and became a steam; large volumes of white vapor, forming suddenly, and rolling back and up. Now I am confident that if the earth had been shaded by trees this rain or mist would have fallen on the ground. This phenomenon can be seen here every hot, dry season. My atten tion was called to it by a question asked while one of these dry thunder-storms was prevailing - the thunder rattling overhead, and not a drop of rain falling. The white mist is not easily observed overhead, where all is light, but opposite the sun under a dark storm-cloud it is very plain, and must attract attention."-Appleton's Popular Science Monthly, IX., 765.

TEMPERATURE OBSERVATIONS IN ITALY.

The distribution of temperature in Italy is the subject of an elaborate memoir by Ragona, as published in the supplement to the Italian Meteorology for 1876.

Starting with the annual movement of the sun, Ragona passes to the remarkable formula that have been published by Liaias, Schmidt, Waltershausen, and others, by means of which the distribution of temperature over the whole earth is represented in a very conspicuous manner. The still more remarkable work of Forbes on this subject seems to have been unknown to him. The detailed study of temperature at Modena from the observations of ten years afforded him an opportunity to make many interesting connections between

temperature and other correlated phenomena, as, for instance, the appearance of the auroras of the 4th of February, 1872, and the 4th of February, 1874.-Meteorol. Ital., App., 1875.

RAINFALL, WINDS, AND PRESSURE IN ITALY.

The distribution of rain in Italy for the years 1871 and 1872 is the subject of an elaborate memoir by Denza, in which, after a careful discussion of actual observations of rainfall and evaporation over the whole of Italy, he considers the theoretical question of the cause of the peculiarities of the distribution of rain in Italy in general, and especially in 1872, and has elucidated the distribution of the winds in Italy. Denza adds to the memoir on rainfall one on the distribution of barometric pressure, as shown by the averages of 1870 to 1875.-Meteorologia Italiana, Supplement, 1875, 41.

THE BORA OF SOUTHERN RUSSIA.

Baron Wrangell has written a very interesting paper on the causes of the Bora, or northerly gales, at Noworossisk. This place, situated on the Black Sea, would, it is said, have the finest harbor in the East, were it not for its exposure to the strong north winds. According to Wrangell, this wind gains most of its force in that locality from the fact that it is a cold wind flowing down the mountain-sides; and as we can not prevent cold dry air from becoming colder by radiation under a clear sky, he proposes to diminish the violence of the wind by cutting a passage through a spur of the mountain in such a way as to relieve the mass of air behind from any confinement whatever, so that the moment a slight increase of density takes place that air will flow away quietly through the artificial valley. The approximate formula deduced by him for computing the velocity of the wind, when the temperature of the air and the barometric pressure are given, is derived from an ingenious course of reasoning, and gives a close approximation to the observed true velocity.- Wild's Repertorium, 1875.

FREQUENCY OF THUNDER-STORMS IN EUROPE.

An investigation into the frequency of thunder-storms during the summer months in Europe has been made by Von

Bezold, who is led to the conclusion that the phenomena of thunder-storms show, in general, during the summer months in the northern hemisphere, two maxima. These maxima approach each other in proportion as we go away from tropical regions. They are scarcely distinguishable in Germany, but are recognized by taking advantage of the observations in Barnaul and St. Petersburg. Of all the stations examined, only one, Katherineburg, shows a single maximum, and the climate of this station is certainly, on many accounts, to be considered as influenced less by the meteorological conditions of the tropical zones than almost any other point in Europe. It is considered therefore that we shall not go far wrong if in the two maxima of electric phenomena, which is so plainly seen in Europe, we recognize an echo of the two summers, or the two maxima of temperature experienced in the tropical zones. - Sitzb. K.-B. Akad. der Wissens., Munich, 1875, 220.

CONSTITUTION OF THE ATMOSPHERE OVER THE LIBYAN

DESERT.

Pettenkofer has examined the air brought back from the Libyan Desert by Dr. Zittel, the companion of Dr. Rohlfs, with respect to the quantity of carbonic-acid gas contained therein. He finds that the atmosphere in the desert has precisely the same chemical constitution as in Germany, where the quantity of carbonic-acid gas varies between two and a half and five ten-thousandths. He has also examined the air contained in the water of springs, and finds the same agreement. Sitzb. K.-B. Akad. der Wissens., Munich, 1874, IV.,

339.

EFFECT OF TIDES ON THE ROTATION OF THE EARTH.

Mr. Tylor, in some remarks on a new theory of tides and waves, advocates the view that the level of the ocean is nearly represented by high-water mark on coasts and bays where there is free access of the tide, or in a channel without a constant flow. He states that he entirely disbelieves in tidal action having the smallest effect on the rotation of the earth, and that the assumption of a great heap of water traveling in one direction is a gross error. He also suggests that some geological difficulties, such as the evidence that tides

during the quaternary periods were three or four times as large as at present, may be explained by periodic changes of position of part of the interior of the earth, rather than by supposing great changes in the distance of the moon from the earth.—7 A, XLVIII., 204.

THE DIMINUTION OF WATER IN SPRINGS, RIVERS, AND WELLS.

The report of Wex on the diminution of water in wells, etc., presented to the Austrian government in 1873, was followed by the appointment, at his request, of a commission of engineers, to whom was intrusted the duty of carefully investigating the points raised by the author in his learned memoir. So important did the matter seem, on account of the long-matured views presented by Wex, that the commission decided to fully investigate the matter. The rivers Danube, Rhine, and Elbe were respectively assigned to certain engineers, while others made measurements in relation to the Alpine streams and the glaciers, and others again undertook a special study of the meteorological questions involved.

During the past two years the committee has accumulated a great mass of valuable material, and has presented a very elaborate report on the subject, which was published in a recent number of the Journal of the Austrian Engineers and Architects' Association. The many details given in the report of the committee may perhaps be summed up as follows: First, an increase is proved in the frequency and the heights of floods in the rivers, as well as a diminution in the altitude of the mean of low waters in most of the rivers and streams of cultivated lands; and all the evil consequences depicted by Wex follow thereon; second, the cause of the injurious changes in the regimen of the rivers, in the drainage of swamps and morasses, in the sinking of lakes and dikes, is principally to be found in the destruction of the forests. These two points having been abundantly established by a large corps of able engineers, the conclusions and the recommendations of the Austrian committee become of the greatest interest to other nationalities, since it is evident that the same causes are at work elsewhere, and especially so in America, to bring about the same disastrous results. The committee recommend that on the one hand exact measures be made of all that relates to the hydrography of the