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examination of aneroids under the receiver of an air-pump has been attempted by Stewart and by Lovering; the comparison of an aneroid with a quicksilver barometer, by carrying both together to high altitudes, has been attempted, among others, by Holtschl. But all these attempts are unsatisfactory, and Schreiber has substituted therefor the following method: An iron receiver is made, in which the aneroid is placed, and which can be closed hermetically by a glass plate. The receiver is then connected with a manometer, so that air can flow in, and furnished with a stopcock, so that air can flow out. The changes of pressure of the air within the receiver are brought about by changing the temperature, which may be elevated to 50° Centigrade, or cooled to -20°, by which means pressures of from 730 to 570 millimeters can be attained. At the higher temperatures successive gradations of pressure are obtained by allowing the expanded air within to escape little by little through the proper cock. In a second paper, Schreiber considers the influences of changes of gravity upon the difference between the aneroid and the mercurial barometer, in which he combats the somewhat absurd theories of Herr von Wullerstorff-Urbair, who, besides a correction for gravity, suggests also a correction for terrestrial magnetism. The unimportance of the latter correction is proved by Schreiber, by simply causing the steel index-needle of the aneroid to be strongly magnetized, in which condition, however, no alteration took place in the reading of the instrument. The latest forms of construction of the aneroids suggested by Kohlrausch, Weilenmann, and Reitz are also elucidated by Professor Schreiber.

In a third communication, Schreiber explains a method of using the results published by Ruhlmann on barometric hypsometry, showing that in Saxony, at least, hypsometric measurements can be made without determining the temperature of the air at the time of observation, but by using the mean daily temperature.

In a fourth communication, Schreiber treats of the differences between the pressure of the air in buildings and in the open air, as brought about through the suction or pressure produced by the wind blowing into or past open windows. Similar effects have been observed and studied by James

and Bache. Schreiber's observations were made in three places at the same altitude, two within houses and the third in the open air. In calm weather the pressure at all three places was the same. As soon, however, as the wind blew even with moderate force the pressure within the house was always lower than in the open air. It was also noticed that in the house the pressure oscillated with the strength of the wind, and every gust of wind was accompanied with a corresponding fall in the barometer; while in the open air the barometer remained quiet. The barometric depression within the house was quite considerable, amounting to one quar ter of a millimeter for a velocity of six meters per second, and 1.15 millimeters for a velocity of 18 meters per second. -5th Bericht Naturw. Gesellschaft, Chemnitz, 1875, 17–22, 26-36.

A NEW FORM OF HYGROMETER.

Among the new forms of the hygrometer, are noted those as made by Lambrecht according to the plan and under the supervision of the inventor, Klinkerfues, of Göttingen. The method of construction of this instrument is not made public, but it is stated that it is always compared with the psychrometer, and that in every respect it is exceedingly trustworthy.-Giebel's Zeitschrift ges. Naturw., 1875, XII.,

300.

THE FORMATION OF SNOW AS OBSERVED FROM BALLOONS. In a balloon ascension on the 29th of November, 1875, Tissandier observed that the fall of small crystals of snow which prevailed at the earth's surface ceased after reaching a moderate altitude. At 700 meters above the earth's surface the temperature was -2° Centigrade. At this altitude a thick cloud spread over the earth's surface, having a vertical depth of 800 meters. Within this cloud the temperature sank to -4° Centigrade. At 1500 feet above the upper surface of the cloud was found a stratum of ice crystals to the depth of 150 meters. Above this the temperature of the air was 0. The snow crystals had a very remarkable appearance; and the rise in temperature at this altitude depended undoubtedly upon the formation of the crystals and the evolution of latent heat.-19 C, 1876, 66.

RIVER CURRENTS AS AFFECTED BY THE EARTH'S ROTATION.

In Dr. Giebel's Zeitschrift, Dr. Dunker gives a somewhat elaborate essay on the influence of the rotation of the earth on the course of rivers, in which, after referring to his first memoir published in 1860, he refers to that of Von Bayer on the same subject, and states that his conclusion that rivers flowing either northward or southward in the northern hemisphere should have their right-hand banks steeper, higher, and more rapidly eaten away, applies also to the southern hemisphere, with the exception that there the left-hand banks are affected in that way. The further consideration of this subject leads him to the consideration of the movement of the winds on the earth's surface, and he gives a general formula, published first by Hollbaur, as applicable to the movement of any body on the surface of the earth, whether solid, gaseous, or liquid. Dr. Dunker seems to consider only bodies moving in the meridian either northward or southward, and treats at some length of the influence of the river in excavating and changing its channel.- Giebel's Zeits. ges. Naturw., 1875, 463.

THE INTERNAL TEMPERATURE OF THE EARTH.

The origin of the interior heat of the earth is treated of in a few words by Professor Mohr, who states that if the interior is still molten, it follows that the nearer we approach this nucleus, not only must the temperature increase, but must do so in an increasing ratio; so that for a given increase of temperature we require to penetrate into the interior of the earth through a decreasing number of feet. Now the deepest artesian well as yet executed is at Sperenberg, about twenty miles south of Berlin. This well was begun in 1867, and has already reached a depth of over 4000 feet, at which depth Magnus measured the temperature (38.5° Reaumur) by means of his geothermometer. The observations of temperature that have been made in this well were executed with the greatest care; each position of the thermometer being cut off from connection with the upper or lower portions of the well by plugging up the tube. The most probable results of these measures are given in the following table:

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There results from these measurements a very remarkable but well-established result-that the rate of increase of temperature is continuously growing less as we descend. This increase diminishes at the rate of one twentieth of a degree for every hundred feet, so that it is easy to compute at what depth the temperature will cease to increase. This depth is found to be the very moderate one of 5190 feet, at which a temperature of about forty degrees might be expected to prevail. Even if we do not attribute absolute accuracy to these observations, yet we see that a constant temperature must be attained at a depth far within twenty miles; and that the temperature itself even at that depth must be far less than the melting-point of the rocks. The result of these observations at Sperenberg is therefore completely in accordance with those deduced by Vogt from operations at the artesian well at Grenelle; and if we attribute any value at all to these calculations, they seem to give a death-blow to the Plutonic theories of former geologists.-Verhandl. Naturhist. Vereins, Bonn, XXXI., 267.

EARTH TEMPERATURE AT KÖNIGSBERG.

The results of a series of measurements of the temperature of the earth, as made at different depths in the botanical garden at Königsberg, has been communicated by Dr. Dorn to the Physical and Economical Society of that city, who remarks that while the series is of too short a duration to justify a very extended investigation, yet one thing is remarked, viz., that the annual mean temperatures as derived from the deeper thermometers are invariably lower than those derived from the surface thermometers instead of being higher, as is usually the case. This anomaly, however, is abundantly explained if we consider that the winters of the years 1869, 1870, and 1871 were of an exceptionally low temperature; and this wave of cold had, in 1873, only just reached the depths in the earth at which the lower thermometers were placed,

while the upper thermometers during that year were exposed to an unusually mild temperature.-Schriften Ostpreussische physikalisch.-ökonom. Gesells., Königsberg, XV., 18.

THE INTERIOR STRUCTURE OF THE EARTH.

The mode of formation of the inequalities of the earth's surface forms the subject of a thorough study by Osmond Fisher, in a memoir published in the twelfth volume of the Cambridge Philosophical Transactions. He concludes that the molten earth first solidified from the centre, and, after a time, from the surface also; so that there is probably at present a thin layer of molten material between the solidified crust and the solidified interior; and that the solid crust therefore rests in corrugations upon a liquid or quasiliquid layer. The conditions of equilibrium of such a crust are, first, that it must be considered flexible; second, it must be in unstable equilibrium; and, third, therefore oscillations of the surface are possible. Mr. Fisher makes an approximation to a rigorous mathematical investigation by inquir ing what form would be assumed by a heavy, flexible crust resting upon a liquid in a rectangular trough shorter than the crust; and shows that when any extraneous force acts upon the crust, it will assume the form of a series of equal circular arcs. The same conclusion holds good when the trough is supposed to be very long, and opened lengthwise into a circular form corresponding to the surface of the earth.

The further conclusions of Mr. Fisher are expressed in the mathematical equations introduced by him. Cambridge Philosophical Transactions, XII.

THE THERMAL SPRINGS OF THE UNITED STATES.

A very complete list of thermal springs in the United States, with the temperatures of their waters as far as they have been observed, is given by Mr. G. K. Gilbert, of the Survey of the Territories West of the Mississippi. He considers the thermal springs as being a valuable indication of the method by which inequalities of the earth's surface have been formed. Hot springs are generally found where the rocky structure is such as to admit of easy communication with subterranean waters. Tilting and fracture of strata are F

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