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ures are the most refined of modern times. He attains an accuracy of the twenty-five-hundredth part of an inch, in his results rivalling the new normal barometer constructed by Wild.

There have come to hand from the India Office Blanford's pamphlets of Instructions to Observers and Tables for the Use of Observers, both of which correspond in every way with the latest views of meteorologists. We note as to his tables for the psychrometer that Blanford has computed them for barometric pressures of from 29.7 to 18 inches, thus allowing the use at each station of a table adapted to its own altitude. He has also introduced the correction to the tension of vapor for reducing barometric heights to gravity at 45° latitude, a correction that is quite sensible, but ought not to be applied unless all the barometric readings are similarly corrected, as has been done by Ferrel in the isobars on his charts of the earth on a polar projection.

Professor Mendelleft, of St. Petersburg, author of a wellknown hand-book of chemistry, has announced his intention to devote to the prosecution of atmospheric studies by means of balloons all the profits of his published works for the next five years. He will probably begin by constructing a captive balloon holding from 50,000 to 70,000 cubic feet of gas.

Some interesting facts deduced from observations made during balloon voyages near Nashville, Tennessee, under the conduct of the well-known aeronaut Professor S. A. King, of Boston, are given in the Signal Office Monthly Weather Reviews during the year.

The highly important observations of clouds and currents of wind by means of toy balloons continue to be daily made at Paris, under the patronage of Secretan. No more promising field of research has of late years been opened up to meteorologists, and its economy places it within every one's reach.

Bell's telephone proves to be so exceedingly sensitive to disturbing currents that it is said that the occurrence of a thunder-storm anywhere within the horizon was made evident by a peculiar class of noises-indeed, storms still out of sight have thus preannounced their approach, and it is suggested that this instrument may prove a highly useful addition to the equipment of the meteorological observer.


CONSTITUTION AND PROPERTIES OF THE AIR. Mr. G. W. Hill, of Nyack, New York, contributes to the July number of the Analyst a paper on an empirical formula for the volume of atmospheric air at any temperature and pressure. Starting with the fundamental assumptions (1) that under constant pressure the ratio of volume to temperature is constant, and (2) that the constant ratio is itself function of the pressure, he shows that Regnault's observations of the volume and tension of air, intended as a test of the law of Boyle and Mariotte, lead to the conclusion that this law is exactly true only at the temperature of 130° C., and that the coefficient of expansion under a constant pressure is 0.0036445 at a pressure of zero, whence it increases up to 0.0038618 at a barometric pressure of 21,5 meters, or about twenty-eight atmospheres.

The carbonic-acid gas in the atmosphere has been observed by Farsky at Tabor in Bohemia, altitude 1400 feet. Daily observations for one year gave a mean value of 3.43 volumes in 10,000, or 0.034 per cent. The quantity of this gas increased with the variability of the weather.

Winkelmann shows that observations lend probability to the theoretical conclusions of Von Obermayer that the coefficients of conduction for heat of air and hydrogen have different and not the same ratios at different temperatures. Similarly Von Obermayer has shown that the coefficient of friction for hydrogen increases with the temperature more slowly than does that for the air. These results are confirmed by a more recent investigation by Pulitz.

The absorption of radiant heat by aqueous vapor has been treated of very well by Haga, who reviews the work of Hoorweg, and concludes that a column of saturated air at 17° or 18° C., one meter long, absorbs 3 per cent.; 3.3 meters long, 10 per cent. of the heat radiated from a Leslie cube at 100° C. Besides these, Buff, of Giessen, bas also shown that aqueous vapor is far more, and dry air far less, diathermanous than was maintained by Tyndall. Their results materially effect some meteorological theories.

Lins shows how observations of halos may be utilized to determine the dew-point at high elevations in the air.

Kummer has, in the Berlin Abhandlungen, continued his investigations into the resistance of air to projectiles.

TEMPERATURE AND DIATHERMANCY. Our knowledge of the transparency of our atmosphere is reviewed by Ricco in the Memoirs of the Italian Spectroscopic Society; he gives an instructive collation of the coefficients of transmission of the total solar radiation and also the separate coefficients for the purely luminous rays. Some observations made by Provenzali at Rome with the lucimeter are here published for the first time.

Numerous papers relative especially to the diathermancy of the atmosphere have been published in France principally by Crova.

Wielenmann's important memoir of 1872, on the temperature of the atmosphere as deduced from purely geometrical and physical relations, and in which he successfully reproduced the observed hourly temperatures for stations over the whole globe, has now been followed by an almost equally successful deductive treatment of the subject of evaporation and atinospheric moisture. A translation by Freeman of Fourier's "Analytical Theory of Heat" has been published by the Cambridge Press.

Dr. Stilling, in studying the cold period of May, 1876, in Russia, shows that it depended on the formation of barometrical minima, which passed from the Baltic to Southern Europe.

Careful observations and study of the temperature and humidity of the air at different altitudes have been made at Upsala by Professor Hamberg. By means of thermometers attached to high stationary posts, Hamberg has studied the influence of altitude per se, while by means of small movable posts he has investigated the influence of the nature of the surface soil. Some of his results are briefly as follows: During clear weather, and at least from two hours before sunrise to two hours before sunset, the temperature of the air is lower than that of the earth on which it rests. The fall in temperature preceding sunset is greater near the earth than at greater heights. The latent heat evolved during the formation of dew arrests the fall in the temperature, but not to the extent that some suppose.

After the dew is deposited, the temperature may sink even to below the freezing-point; but as soon as the dew changes to hoarfrost, the temperature of surrounding air rises to 32° Fahr., and even above, while higher up the strata of air continue to be even below 32°. The isothermal surfaces near the earth during the night are not always horizontal or parallel.

Hellmann, in a memoir on the variability of the temperature in Northern Germany, gives many comparisons of local interest, especially relative to the influence of the Baltic and North Sea.

In an important memoir on the annual temperature period, Ragona first deals with the theoretical formulæ, and then applies them to observations at Modena, Bologna, Milan, and Geneva. He shows that the radiation of heat at night from the earth is proportional to the solar radiation received during the day. Among the many very interesting results of his investigation, he gives formulæ representing the annual changes in the daily maximum and minimum temperatures, and shows that the mean of these two formu. læ represents the mean annual temperature.

WINDS AND CURRENTS. Anything that draws the attention of observers to the importance of observing the actual heights and movements of the clouds is to be welcomed, and we note, therefore, the little work of A. Ringwood, of Australia, in which he gives some methods, but by no means exhausts the subject. The methods that have been proposed and used are now so numerous and various that any one who will may easily make these important measurements. Among these is one proposed by the author in 1873, but not yet published: it consists essentially in throwing a beam of light vertically, or at any determined angle, by means of the reflectors used in public illuminations; an observation from a neighboring station of the spot of light on the under surface of the clouds gives their altitude; so that both by day and night the elevations may be determined. The formulæ, etc., for use in applying the photographic camera to this purpose during the daytime were communicated by the author in 1871.

Captain Miejahr gives in the Hansa a series of articles on clouds and winds of the coasts of China and Japan, which will be found to be eminently instructive.

The importance of systematic observations on the movements of the clouds continues to be frequently urged. Clement Ley calls for as many co-operators as possible in this work, and Broun has carefully discussed his own most exact observations. Hildebrandsson has published, with numerous charts, a new edition of his studies into the movements of the upper currents of the atmosphere. None of these works, however, seem to be comparable in extent and importance with the magnificent series of maps that have now for seven years been published thrice a day by the Army Signal Office. These maps and the accompanying bulletins show the direction of the winds, the lower clouds, and the upper clouds; and as early as May, 1872, the author announced the law that the upper clouds moved towards a point to the right of the direction of the lower clouds, and subsequently that the lower clouds also moved to the right of the surface winds. He also stated that the prevalent mistaken idea that the upper currents were all from the west, or that a steady west current prevailed at great altitudes, arose from studying only cirrus clouds, which were, at least in the United States, generally found on the west sides of centres of high pressure (see Bulletin Phil. Soc., Washington, 1871). The exact inclination of direction of lower cloud movement to the winds was first determined by Redfield in 1833–39, as about 7o. In the previous year Redfield had estimated at 45° or less the angle between the winds and the radius drawn to the storm-centre.

Buys-Ballot has published an extended discussion of the relation between the theory and observation relative to the connection between barometric pressure and the wind. To a certain extent this is an examination into the truth of the law known as Buys-Ballot's law, and published by him in 1857. This law has been so often modified by others as to have quite lost the simplicity of the wording of the author, who originally announced it thus: “When at two stations in Holland the deviations from normal pressures are unequal, the wind will, within twenty-four hours, be found to blow at right angles to, or within 30° on either side of, the line joining these." According to his present investigations, Buys-Ballot finds that the east and northeast winds set in less promptly than the west winds; and with regard to the gradients, he finds that these winds need a steeper

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