those predicted by theory. The principal source of discordance is probably to be found in the fact that the computations take account only of the pressures against the front surface of the solid, while the reaction that takes place on the hinder surface is partly or even totally neglected. In the case of the anemometers employed for the purpose of measuring the velocity of the wind, probably without a single exception, their indications must be interpreted by means of approximate empirical formula; and no other method has, as yet, been devised by which the indications given by pressure gauges can be compared with those given by velocity meters. Of these latter instruments, the best are those known as Robinson's anemometer and the Casella anemometer. Of the pressure gauges, those most commonly in use are the Ossler anemometer and Wild's anemometer. Dr. Dohrandt has recently undertaken, at the instigation of Dr. Wild, of St. Petersburg, an elaborate investigation, both theoretical and experimental, into the sources of error peculiar to these instruments; and the memoir embracing his results, which was announced a year ago by Professor Wild, seems to be the most valuable contribution to anemometry that we have had occasion to regard since the appearance, in 1873, of Cavallero's investigations, which were noticed by us at the time. (See Annual Record, 1874, p. 104.) Unfortunately, Dr. Dohrandt was interrupted in his labors by a call, on the part of the Russian Geographical Society, to superintend the establishment of meteorological stations in Asia; but Professor Wild assures us that his researches will be continued by the Physical Observatory, until definite conclusions can be considered as established. Among the means adopted for comparing the actual velocity of the wind with the readings of the anemometer, Dr. Dohrandt experimented first with the method adopted thirty years ago by Duchemin, and less thoroughly by others, and which consists in carrying an anemometer attached to a locomotive, the velocity of whose movement is well ascertained. The railroad from St. Petersburg to Tsarskoe Selo offered a good opportunity for the experiment which was first made on July 1, 1871, in which the average velocity of the railroad train seems to have been from twenty-one to forty-eight kilometers per hour. During the experiment the average velocity of the wind itself, in

the direction of the path of the locomotive, was two and eight-tenths kilometers per hour; and the velocities observed by timing the train as it passed each mile - post agreed with the velocities recorded by the anemometer to within two per cent. A more definite method of investigation, however, is that of Combes, which consists in attaching the anemometer to a long arm, which latter is made to revolve in a circle at a known rate, in a space where strong currents of air do not occur. Velocities up to forty kilometers per hour were attained in this way by Dohrandt; and from the investigation of six different Robinson's anemometers, and of two of Casella's instruments, and of a number of electric recording anemometers, it was concluded that the arithmetical mean of the indications of an anemometer, when the arm which carried it revolved in both a positive and a negative direction, might be adopted as the result that would be given if the instrument had simply moved in a straight line. The determination of the effect of the moving anemometer upon the air surrounding it-an effect which it is known consists essentially in carrying the air with it, and thereby diminishing the relative velocity of the air and the instrument—was first made by placing a Casella and a Woltman's anemometer on the same level with the rotating anemometer, but fixed in their positions, and so near to the circle described by the latter that they could feel the influence of the wind dragged along by the Combes' apparatus, and be thereby set in motion. As the result of this portion of his investigation, Dohrandt finds that the wind due to the dragging influence of the moving anemometer is very ap proximately proportional to the velocity of the latter itself. As a final result in reference to the velocity of the anemometers, Dohrandt gives a formula applicable to each one individually, by means of which the true velocity may be com puted from the indications of the dials of the instruments. Having thus some half-dozen well-investigated instruments as standards, it becomes easy to compare numerous others with these. The result of such comparison showed that the errors determined in this secondary manner were of the same nature and expressed by the same formula as those determined by the original investigations. In general, in relation to the velocity of the anemometers, Dohrandt finds that the

centre of the revolving caps of the Robinson instrument, instead of describing exactly one third of the path of the wind, as they should do according to the theoretical researches of that astronomer, differ from this to such an extent that the indications of their dials must be multiplied by numbers varying from 2.1 to 2.9 in order to deduce the true velocity of the wind. The result most to be desired in relation to this branch of anemometry is the determination of the relation between these varying factors and the actual dimensions of the respective instruments. But Dr. Dohrandt finds, as had Cavallero and Stowe before him, that no such relation can be discovered; only so much is easily seen, that the magnitude of the factor is in more direct connection with the diameter of the hemispherical caps than with the length of the arms of the anemometer. In respect to the pressure of the wind, Dohrandt experimented with six different specimens of Wild's wind-pressure anemometer, which consists simply of a very thin plane piece of iron or wood, or thin cardboard, hanging by a very thin arm from a pivot, and which is by the force of the wind pushed aside from its vertical into an inclined position. The angular extent of the deflection is measured in degrees by an appropriate divided arc. In connection with this, he calls attention to the fact that the indications of this, and of all pressure instruments, are decidedly affected by the density of the atmosphere, as indicated by the barometer. The comparisons of the indications of this pressure gauge with the velocity deduced from the standard anemometers seems to show that the simple instrument of Dr. Wild suffices, by means of the table given by Dohrandt, to determine the velocity of the wind within less. than about one half a meter per second. On account, therefore, of its simplicity and inexpensiveness, it is probable that this instrument will be widely used throughout the world, especially as it has now been introduced at all the Russian meteorological stations, and at many of those in southern Europe.-Wild's "Repertorium," IV., art. 5.

THE SELF-REGISTERING BAROMETER OF REDIER.

Among the many contrivances brought forward during the past few years for the self-registration of meteorological instruments, that of Redier seems both economical and ap

plicable to many cases where more troublesome apparatus would be out of place. His arrangement consists essentially in such an alteration of the well-known printing barometer constructed by G. W. Hough, of Albany, that the use of electricity is done away with, and, on the other hand, the fulcrum of the principal lever in the apparatus is fixed, while the barometer tube itself, or the aneroid box, moves. The numerous specimens of the apparatus constructed by Redier for individuals in France seem to have given very general satisfaction, and the instrument has been highly commended to the attention of French observers. It consists essentially of a clockwork by means of which a cylinder is made to revolve uniformly, carrying with it a sheet of paper upon which the record is to be made. Above the cylinder stands the barometer, which is so arranged that the rise and fall of a thousandth part of an inch causes a lever to rise or fall by a corresponding movement, thereby releasing the detent of an auxiliary piece of clockwork, which is thereby at once set in motion. The movement of this clockwork allows the barometer tube itself to fall or rise, thereby again interfering with the movement of the clockwork and automatically stopping it. Meanwhile the up or down movement of the barometer has been closely followed by the corresponding movements of a pencil, whose mark on the sheet of paper produces an exact record of the extent of the barometric change.-13 B, III., 267.

DO STORMS CROSS THE ATLANTIC ?

Mr. Ley states that, having worked for a considerable time at the comparisons of United States with European weather charts, he concludes that only a small portion of the storms experienced on the American side of the Atlantic can subsequently be distinctly traced in Europe. Of those thus traceable the majority are felt severely in the extreme north of Europe. The rapidity of the progress of these storms across the Atlantic varies indefinitely, and could not be deduced, as Mr. Draper has attempted, from the velocity of the winds experienced in them. Many of the most destructive European storms occur when the barometric pressure over the eastern portion of the United States is tolerably high and steady, and they appear to be developed upon the Atlantic

Ocean, near the eastern limits of the area of high pressure.— 12 A, 405.

GLACIATION OF ICELAND.

In the opinion of Mr. William L. Watts, who is engaged in making some explorations among the glaciers of Iceland, these are increasing year by year; and he thinks that at no distant period the whole island will be covered with ice, as is the case with Greenland.—13 A, 193.

GLACIERS OF THE HIMALAYAS.

At the recent meeting of the British Association Colonel Montgomerie gave an account of the glaciers of the Himalayas, which are most developed in Baltistan, in Northwestern India. According to his statement, these glaciers gradually increase in size from east to west, many of them being more than twenty miles in length, and one, Biafo, thirty-four miles. The thickness of the ice was in some cases found to be 400 feet. The phenomena of progress, etc., were found to be similar to those observed in the Alps.-15 4, September 4, 314.

TIDES OF THE MEDITERRANEAN.

The tides of the Mediterranean form the subject of a prize essay by Stahlberger, of Hungary. The author especially dwells upon observations and discussions relating to the peculiar local influences in the neighborhood of the port of Fiume, on the shores of the Adriatic. Pursuing an inductive method, he shows the existence of general changes of the water produced by cosmical causes, and local changes. due to meteorological or local agencies. Of the former there are principally two oscillations dependent on the sun, and two on the moon. The local changes are caused chiefly by variations in the wind and the barometer. In stating this view, he seems not to have gone beyond what Mr. Ferrel has already published with reference to the Atlantic.-"Mitth." Austrian Hydrogr. Office, II., 723.

DAILY WEATHER CHARTS.

The dissemination of valuable meteorological intelligence has been remarkably facilitated in England by the daily publication, in the London Times, of a small weather chart, show