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laws controlling the movements of the atmosphere is somewhat unsatisfactory to the professional student.

APPLICATION OF AMSLER'S PLANIMETER TO METEOROLOGICAL CALCULATIONS.

Mr. Scott, of the Meteorological Office in London, reports that perfect success has attended the adoption of Amsler's planimeter in the calculation of the average daily temperatures. The instrument was applied directly to the photographic sheets of the self-recording instruments, and was also applied to the reduced copies of these sheets, as published in the quarterly weather reports, and the results thus obtained check each other satisfactorily.

RAINFALL AND SOLAR SPOTS.

In the monthly notices of the Meteorological Society of Mauritius, Mr. Meldrum, of that island, concludes that, whether we take the annual rainfall for the largest possible portion of the globe for short periods, or for a small portion of the globe for a longer period, we arrive at the same result: viz., an increase of rain at or near the epochs of maximum sun spots, and a decrease of rain at or near the epochs of minimum sun spots. The exceptions to this law are few and trifling, and disappear from the results as the inquiry is made to cover more extended portions of the earth's surface and a longer interval of time.-12 A, X., 418.

THE DRY SEASON OF BRAZIL.

As an illustration of the extreme dryness of the soil during the dry season in Brazil, it is stated that, in June, all vegetation ceases, the seeds being then ripe or nearly so. In July the leaves begin to turn yellow and fall off; in August an extent of many thousands of square leagues presents the aspect of a European winter, but without snow, the trees being completely stripped of their leaves; the plants that have grown in abundance in the wilderness drying up, and serving as a kind of hay for the sustenance of numerous heads of cattle. This is the period most favorable for the preparation of the coffee that grows upon the mountains. The beans are picked and laid on the ground, which gives forth no moisture, but on the contrary absorbs it, and being

surrounded by an atmosphere possessing the same desiccating properties, the coffee dries rapidly without becoming mouldy. The Empire of Brazil, p. 23.

REPORT OF THE SIGNAL SERVICE OBSERVER ON PIKE'S PEAK. The Signal Service observer on the summit of Pike's Peak reports that the local storms there experienced originate over the parks to the westward, on hot afternoons. On one occasion he was favored with an excellent view of the interior structure of the clouds of a tornado, when he observed that while the cloud-bearing currents of air float toward the centre they had a decided downward movement, but that masses of smoke-like vapor rapidly ascended through the interior funnel.

THE FREQUENCY OF STORMS.

Köppen has made an investigation of the frequency with which barometric minima occur in Northwestern Russia. He finds that during the years 1872 and 1873 107 cyclones occurred, lasting altogether 393 days, the mean duration of each one of these being about three and seven-tenths days. According to a table given by him, if a barometric depression is just leaving the observer, it is probable that within one or two days a second cyclone will occur. If, on the other hand, many days have elapsed since the passage of a depression, and uniform and high pressure has prevailed, then the probability that a new depression will arrive within twenty-four hours is diminished by one half.-19 C, VIII., 86.

THE PASSAGE OF STORMS TO EUROPE FROM AMERICA.

The great storm that passed over the coast of Germany on the 22d of November, 1873, has been investigated by Prestel, who concludes that it was identical with the storm that left the United States on the 18th day of the same month, which was at the time distinguished as a severe disturbance. In his remarks upon this subject, Mr. Prestel possibly goes too far in attempting to show that certain storms recur at certain epochs of the moon, but he is nevertheless probably nearly correct in saying that many attempts to trace lunar and other periods in the changes of the weather have, as yet, had only a negative result, because we have considered only

observations referring to a single place. It may, in fact, be stated that the currents of the atmosphere never follow precisely the same routes, nor have precisely the same effects; consequently individual places on the earth's surface are at one time within, at another time beyond, their influence, and the weather at one point shows nothing of the periodicity that may possibly regulate the movement of the current itself. Under these circumstances, the observed local readings of the barometer, temperature, rainfall, etc., can not be expected to follow any such laws of periodicity as may possibly be followed by the atmosphere as a whole. The periodicity of atmospheric phenomena can, actually, only be properly investigated when we combine the geographical details with the element of time. Following this idea, Prestel feels justified in the conclusion that certain storms which have visited the earth have passed over nearly the same paths at their successive apparitions, which latter always occur when the moon returns to about the same position with reference to the earth. As this can only happen every nineteen years, it follows that the storms of 1873 are to some extent a repetition of those of 1854.-Zeitschrift für Meteorologie, IX., 224.

CAUSE OF THE WARM CLIMATE OF THE WEST COAST OF NORWAY.

Professor Karsten, in an address delivered before the Society of German Scientists and Physicians, stated that the comparatively mild temperature which characterizes the west. coast of Norway is not, as has been hitherto considered, the effect of the Gulf Stream, but of a warm current of water that leaves the Baltic when the cold weather sets in.—13 A, November 21, 1874, 560.

CONNECTION BETWEEN THE SEASONS AND HUMAN MORTALITY.

Messrs. Mitchell and Buchan have made a very thorough study of the influence of the seasons on human mortality, basing their investigations on thirty years of observations at London. The greatest mortality is above the average from November to April; falls to a minimum at the end of May; then rises to a maximum on the third week of July, continuing there until the second week of August, and falling thence to a secondary minimum in October. Deducting the summer

excess, which is due to one section of the population (namely, infants) and to one class of diseases (namely, bowel complaints), there remains an excess in the cold and a deficiency in the warm months, which is due to the diseases of the organs of respiration.-12 A, X., 210.

THE DISTRIBUTION OF THUNDER-STORMS.

Hildebrand has investigated the distribution of thunderstorms in Sweden for the year 1871, basing his study upon the observations of about two hundred and fifty stations. The number of days on which thunder was observed varied between one, two, and three in March, April, October, and November, to twenty-seven in July. Thunder-storms are found to be less frequent, not only in the cold months, but also as we proceed northwest. With regard to the daily distribution of these storms, he shows that the greatest number have occurred between 4 and 6 P.M.; the least have occurred between 10 P.M. and 6 A.M. The greater number of thunder-storms come from the northwest; whence also come the clouds and wind. Le Verrier has long since shown that in France the thunder-storms occur on the advancing side of the general atmospheric disturbances, and that they follow the movements of the cyclones; but that, on the other hand, many thunder-storms are purely local. Mohn has likewise studied the subject in Norway, and comes to conclusions quite similar to those of Le Verrier. Mohn has furthermore shown that the origin of the thunder-storm is to be found in the ascent of warm, moist currents of air. These latter, however, also develop in connection with volcanic eruptions accompanied by whirlwinds, and also when the lowest strata of air are overheated in the hottest hours of the day. He therefore classifies the thunder-storms as whirlwind thunderstorms and heat thunder-storms. The former originate on the advancing side of cyclonic storms, and follow their movements over entire countries. The latter class originate on the hot summer afternoons, and are to be considered as purely local phenomena. If, however, we combine the observations of Mchn and Le Verrier with those of Breitenlohner, it will appear difficult to make so sharp a distinction as Mohn has attempted, since both causes are acting at the same time; so that extended and regularly advancing thunder

storms co-exist with merely local ones. The latter are, indeed, generally sporadic, and especially frequent in favorable localities, such as mountains and forests. A passing cyclonic storm is always favorable to the formation of local thunderstorms. The peculiarly favorable conditions that prevail at certain localities are shown in a very interesting way in the work of Prettner on the climate of Carinthia. - VierteljahresRevue der Naturwissenschaften, II., 11., 190.

A NEW BAROMETER OF LARGE SCALE.

The great desirability of being able to observe the slightest changes in atmospheric pressure has led to the production of many more or less unsatisfactory barometers, of which in general it may be remarked that, although they do really afford us a highly magnified scale of movement, yet the moving parts are themselves so weighty that the sluggish behavior of the instrument entirely neutralizes the advantage which was sought, so that the slight momentary changes in atmospheric pressure still pass by unperceived. To meet these difficulties, Mr. Hirn, one of the most eminent French philosophers, has described an instrument which he calls the Megabarometer: his apparatus consists of three vertical glass tubes, closed at their ends, and connecting with a horizontal tube by means of iron sockets. The middle tube, filled with mercury up to half an inch of its top, is a true barometer. Its neighboring tube on the one side has about four millimeters' internal diameter, while the other tube has one millimeter diameter, but is soldered at its top to a closed bulb of about four centimeters' internal diameter. The lower half of this bulb is filled with mercury, the upper half with alcohol. The first of the three tubes thus constitutes a barometer composed of two liquids, and the variation of level in the two open tubes on the right and the left hand is very nearly in an inverse ratio to the densities of the liquids; so that a change of one inch in the height of the mercury brings about a change of seventeen inches in the alcohol tube.-Nouvelles Meteorologiques, p. 34.

MIRAGE.

In some remarks on the phenomena of mirage, Professor Everett states that when a ray of light is passed through a

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