works of Ferrel on this subject.-Vienna Zeitschrift für Meteorologie, 1875, 290.

THE EUROPEAN DROUGHT OF 1875.

The period of great drought, which lasted from February to April, 1875, in Europe, has been treated of by M. Lancaster, aid at the Royal Observatory of Brussels, who states that this period merits our attention. The rainfall during these three months has never, since 1833, been so small as during this year. The mean of the forty-two years of observations at Brussels gives for the three months 144 millimeters, while the height for 1875 is only 46 millimeters, or less than one third of the normal height. The pressure of the air has generally been high. The temperature has been subject to considerable variations, having been on the whole slightly below the average. The wind has presented the most interesting phenomena; the predominance of northern currents. during March and April is especially remarkable. The drought extended even to the middle of June, although by that time a little water had fallen.-Bullet. Acad. Roy. de Belgique, 1875.

GLAISHER'S OBSERVATIONS OF MOISTURE IN THE ATMOSPHERE.

In the annual memoir at the opening of the Gymnasium at Sondershausen, the Director, Dr. Kieser, in an essay on the moisture in the atmosphere, states that he has carefully computed the extensive series of observations made by Glaisher in reference to the absolute and relative humidity at different altitudes. His results are presented in tables, showing the state of the atmosphere at every one hundred meters from the earth's surface up to a height of six thousand meters. He concludes, first, that it is demonstrated that the absolute humidity diminishes with the altitude, although exceptions are not uncommon; second, that therefore the surfaces imagined to be drawn through the atmosphere defining the regions of equal quantities of vapor have a wave shape, depending upon purely local circumstances; third, the quantity of vapor is different at the same altitude in different months; fourth, the density of the vapor diminishes much more quickly than the density of the air as we ascend. Thus the density at five thousand meters is about half of that at

the surface of the earth, while the quantity of moisture at that altitude is, during August, from a fourth to a fifth, in September an eighth, and in April less than a tenth of that observed at the surface of the earth; fifth, at altitudes of six or seven thousand meters the absolute humidity is very small throughout the year, and less than one grain of vapor is to be credited to every cubic meter of air; but at the greatest altitudes that have been reached there has been found no perfectly dry air. Thus the relative humidity increases as we ascend from the earth's surface until we reach the level of complete saturation, but above the clouds the diminution of relative humidity diminishes suddenly. The ordinary condition of the atmosphere appears to be that of successive layers of moist and dry air. - Gymnasial Programme, Sondershausen, 1874.

ON THE RAINFALL AND EVAPORATION IN INDIA.

In a memoir by A. R. Binnie on the Magpur water-works, he gives some details with reference to the rainfall and the drainage at Magpur. This city is situated in latitude 21° north, longitude 79° east, at an elevation of about 1000 feet above the sea-level. The average rainfall for the nineteen years from 1851 to 1873 was 40.7 inches, of which 37.5 inches fell during the monsoon months from June to the middle of October. Although the general fluctuation of rainfall in India is similar to that in other parts of the world, yet it has certain well-marked peculiarities, the first of which is that the greater part of the annual rainfall is confined to a few months during the southwest or southeast monsoons; second, the greater part of the year is almost rainless; and, third, during the wet months the rainfall is much more intense than in temperate countries. In the most violent showers that have been noticed in that place the rain fell at the rate of 4.7 inches per hour. To determine the quantity evaporated from the surface of the ground is a matter of difficulty; but Mr. Binnie attempted, by careful observation of the level of the water in the receiving-basin during the dry season, and by comparing the result with the existing meteorological circumstances, to estimate the amount. During that period in which no water ran into the basin, the quantity in the latter diminished, in 242 days, to the extent of seven feet.

The diminution varied from 0.045 to 0.024 of a foot per day. The fluctuation of the rainfall year by year is quite large, and so distributed that on the average sixteen periods of great and little rainfall may be anticipated in every hundred years. Since it has been, during the past few years, suggested that the periods of fluctuation of the spots on the sun's disk bear a relation to the fluctuations of rainfall, similar to those which have been demonstrated in the case of terrestrial magnetism, Mr. Binnie has sought to test the truth of this statement by making a comparison between the fluctuations of the rainfall at fourteen places and the solar-spot periods from Schawbe's observations; but no satisfactory result or accurate deductions could be drawn from this test.-Journal Institution Civil Engineers.

ON THE THEORY OF HAIL.

Renou having proposed some objections to the theory of the formation of hail which Faye has recently had occasion to develop in connection with his theories relating to storms, he has replied to Renou, to the effect that hailstones are, in general, formed by successive accretions of coatings of ice, which latter are due to the cooling of the air to a point below its dew-point and below the freezing-point. Admitting that the nucleus may have a very low temperature, the same, viz., as that of cirrus clouds, it is easy to see that in virtue of this low temperature it will congeal around it a thin layer of transparent ice, and that, if the physical and mechanical conditions where it is remain the same, the hailstone will be kept at a temperature in the neighborhood of the freezingpoint, and will, by the consolidation of the thin envelope and evolution of heat, no longer continue to grow, but need again to be cooled. The thickness of the shell thus formed after any one exposure to the moist air can not exceed one twelfth of the diameter of the nucleus.-6 B, LXXXI., 513.

RAINFALL OF BOHEMIA.

Among the recent monographs upon meteorological specialties, we notice a memoir by Professor Studnicke, read before the Bohemian Scientific Association of Prague, on the rainfall of Bohemia. The climatology of Bohemia has been most exhaustively investigated by Kreil in his work of that

title, published in 1865; but in the matter of rainfall Studnicke has had special opportunities which have enabled him, to say nothing of the lapse of the past ten years, to present the fullest particulars and material. Thirty-eight stations were indeed represented in the memoir of Sonklar on the hyetography of Austria; he was, however, unable, even with this number of stations, to properly represent the southeastern portion of Bohemia. The gaps that were necessarily found in Sonklar's and Kreil's works have been filled up by Studnicke, who was three years ago put in charge of the meteorological section of the committee for the scientific survey of Bohemia, and who has been instrumental in adding about fifty new stations to those already existing. Especial study was made in the neighborhood of Prague, where four new stations were established, in order to elucidate the dif ferences in the records of the older observations.-Sitzb. K. Böhm. Gesellschaft, 1874, 62.

MOISTURE IN THE ATMOSPHERE.

Mariè Davy states that there is kept in active service in the meteorological observatory at Mont-souris a collection. of apparatus for investigating, in a general way, certain physical problems of the atmosphere, especially the quantity of aqueous vapor contained therein. The apparatus consists principally of a large telescope, with silvered objective and a photometric ocular. This ocular consists of a Foucault polarizing prism, behind which is placed a double-refracting analyzer movable about the centre of a graduated circle. By the use of this apparatus we measure the ratio of the intensity of the light given from the sun, and from any part of the atmosphere in its immediate neighborhood; this ratio varies with the state of the sky. A similar operation would give the measure of the apparent intensity of the solar spots. A second telescope of smaller dimensions is mounted equatorially. Its objective is uncovered, and its ocular is similar to the preceding. A disk of white enamel is fixed horizontally on a pillar; at the side of the disk is found a smaller one of copper, which projects its shadow upon the enameled disk when illuminated by the sun. This shaded circle is then only lighted by the diffused light of the sky, while the neighboring parts receive also the direct rays of the sun. The

telescope previously described, or the photometer, gives then the ratio of the intensity of the two lights. Some white disks with black centres placed at various distances give with precision the degree of transparency of the air in day-time. The transparency of the sky during the night can also be found. by the same instrument; but the results differ according as the moon is or is not above the horizon. The thermo-electric actinometer of Dessaine has also been modified in its applications by Mariè Davy. The cyanometer of Arago is also made use of.-Bulletin Mensuel Observatoire de Mont Souris, 1875, 129.

THE OBSERVATION OF POLAR BANDS.

The Wochenschrift, published for so many years by Dr. Heis, of Münster, has lately been transferred to the editorship of Dr. Herman J. Klein, of Cologne, well known to lovers of astronomy by his numerous popular essays. In his hands its interest will not fail of being maintained. Two recent articles by him are especially worthy of notice, one on the importance of observations of that form of clouds ordinarily known as polar bands, which have acquired a new interest owing to the observations and theories of Prestel and Hildebrandsson. In another article Dr. Klein calls attention to the project long since made by Dr. Falb of using the asteroids as a medium for determining the brightness of the faintest fixed stars.-Klein's Wochenschrift, 1875.

TIME OF SETTING SELF-REGISTERING INSTRUMENTS.

In the report of the meteorological section of the Leicester Literary and Philosophical Society, we learn that the time of setting the self-registering instruments has been altered from 9 A.M. to 9 P.M. This alteration has been made in consequence of the recommendation of the Vienna Congress, which has been adopted by the official and by all the principal private observatories of England. A new and more complete graphic method has also been adopted for displaying the daily readings of the meteorological instruments. By this method a whole month's daily readings are now exhibited in tabular form on a single sheet.-Leicester Literary and Philosophical Society's Report, 1875.