Imágenes de páginas
[ocr errors]


The annual spring meeting of the Society will be held in Washington, D. C., at the Central Office of the Weather Bureau, probably on Saturday, May 2. All members of the Society desiring to present papers at this meeting will kindly send titles and abstracts to Mr. W. R. Gregg, Weather Bureau, Washington, D. C., not later than April 7, in order that the full announcement of the program may appear in the April BULLETIN.

(Concluded from January BULLETIN, pp. 1-24)

New Precipitation Maps of California
By B. M. Varney

(To be published in the Monthly Weather Review)
Discussion Prof. R. DeC. Ward remarked that the paper was a good
illustration of the historical development of our rainfall maps.

The Theory of the Anemometer
By J. Patterson

The most common instrument for measuring the velocity of the wind is the cup anemometer; as originally designed by Dr. Robinson it consisted of four hemispherical cups mounted at right angles to each other on arms of suitable length on a vertical axis with a revolution counter to register the mileage; it was assumed that the wind velocity was three times the velocity of the centers of the cups; this relationship is known as the factor. It was not long, however, until it was discovered that the factor was not three and that it was variable. Many investigations, both theoretical and practical, have been made on the anemometer to determine this relationship.

On the theoretical side which is the only part considered in this paper, Robinson, Sir George Stokes, Theisen, Chree and Whipple have all made important contributions, but they did not know the forces acting on the system nor how they acted and were unable to solve the problem completely. Through the kindness of the Authorities of the University of Toronto, the wind tunnel was used to investigate these forces.

The torque or moment of the forces acting on the cup when held stationary in the wind was measured at definite intervals throughout a complete revolution of the cup; by this means the forces acting on the cup were obtained and their law of variation determined. Calling this the static torque it was found that on the concave side of the cup the torque varied as the 2.05 power of the velocity and radius, while on the convex side it varied as the 1.85 power. It was also found that when the convex side of the cup had turned 30° into the wind the static torque was reversed, and caused the cup to turn into the wind instead of away from it. It was also discovered that the higher the velocity of the wind and the larger the cup the more pronounced this became until the torque tended to turn the cup into the wind through the whole 30°. As regards the arms the torque varied as the square of the velocity and as the diameter of the arm.

When a cup is rotating at constant speed in a steady wind, the total force acting on the cup and arm must be zero for a complete revolution. It was found, however, that if the torque for the rotating cup was calculated from the static torque by the laws of mechanics for the resolution of forces, the total torque was not zero, but if the direction at which the relative velocity acted was modified it was possible to get the total torque zero. From these forces it was found that the factor for any anemometer could be expressed by the equation

[merged small][ocr errors]

where ƒ is the factor and K depends on the velocity of the wind, the diameter of the cup and the length and diameter of the arm. It is assumed in this that one cup has no influence on the others.—(Author's Abstract).

Discussion Prof. C. F. Marvin said he regarded the paper as a most important one. It was interesting to note that the investigation had been made possible through the development of the wind tunnel, itself in part a by-product of the discovery and development of artificial flight. Heretofore it had been impossible not only to standardize the anemometer, but even to develop the theory satisfactorily. It was very gratifying to learn that the results of the later work agreed so closely with those that he himself had obtained in 1888 with far less satisfactory equipment.

Mr. S. P. Fergusson stated that he and Mr. R. N. Covert had made some open-air comparisons of the old and new types of anemometers, finding close agreement after applying recently-determined corrections to the old instrument The following figures give the results of one comparison:

[merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

Mr. Patterson, noting the marked reduction in the high velocities above tabulated, remarked that complaints of the new instrument had been made because it does not show enough wind!

The Use of Duralumin in the Construction of Apparatus
By S. P. Fergusson

Duralumin, a new alloy developed in Europe probably during the past ten years, consists of about 94 per cent aluminium, 5 per cent copper and 0.5 per cent each magnesium and manganese, hence resembling the mixture used for aluminium castings. When tempered as steel is tempered it acquires the strength and density of Bessemer steel, but is only one-third as heavy, is easily worked or machined, takes a good polish and probably resists corrosion rather better than does aluminium. It is best known for its use in the frame-work of Zeppelin and other dirigibles, and until recently has been difficult to obtain in America. At the present time, duralumin sheets, rods, tubes and bars, annealed, heat-treated and hard tempered, can be obtained from at least two manufacturers at approximately the prices asked for aluminium.

[ocr errors]

Experiments with samples obtained during the past few months indicate that many if not all scientific instruments now made partly or wholly of aluminium could be materially improved if duralumin were substituted for the aluminium, particularly in instances where both sensitiveness and strength are desirable and where recording and indicating mechanisms are actuated by an elastic element. One example of each class was shown, the first being a cup-wheel of the new standard anemometer, made entirely of duralumin instead of the usual steelbrass-aluminium combination. The new wheel is much stronger than the old, since its weight is at least one-third smaller, it has a more uniform rate and the friction and wear are smaller. The second example is a Richard barograph having a single pivoted recording style instead of the more familiar system employing two levers. The new instrument has three instead of seven pivots, the weights of the intermediate lever and two-thirds that of the recording style are eliminated, thereby reducing errors due to friction, and the cost is smaller than that of the older patterns.

Other examples could be described and many will suggest themselves to all interested in the improvement of instruments of precision.— (Author's Abstract).

Discussion-Mr. J. Patterson said he has used duralumin in many instruments, including the new type anemometer. For castings it is no better than aluminium alloy, but in molded form it is remarkably efficient. One very great advantage over aluminium is that it is apparently unaffected by sea air of sea water, whereas aluminium must be kept thoroughly painted, when used near the sea coast.

Simple Weather Maps by Radio

By V. Bjerknes

At this point in the program the President gave expression to the pleasure that all felt in having as a guest, Dr. V. Bjerknes, Professor of Hydrodynamics at the Bergen Geophysical Institute, Norway, and said he hoped that Dr. Bjerknes would be willing to address the meeting. Dr. Bjerknes told briefly of the work, inaugurated a year or so ago, of sending out information by radio that enables sea captains to draw a simplified weather map. The occurrence of fog is of paramount interest and its prediction is very important. The messages, therefore, include, so far as possible, the data that will show the regions in which fog is occurring or is likely to occur, particularly the positions and intensities of the warm fronts and cold fronts and the locations and extreme pressures of centers of low and high pressure. In addition, the sea captains can of course pick up barometer and other observations from nearby ships and can and do note the conditions of the sky, etc. The messages furnished are much shorter than those necessary for drawing a complete weather map. They have been found very useful to ships on the Iceland-Europe route, but have not yet been taken up generally. He believes this scheme will find increasing favor, as experience demonstrates its value.

Ice Ribbons

By W. J. Humphreys

Following Dr. Bjerknes' talk, Dr. W. J. Humphreys presented an interesting informal communication illustrated by lantern slides on “Ice Ribbons." Some time before, he had seen ribbon-like formations of ice leading out from the stalks of rock mint. It appears that these dead stalks retain water in their capillary tubes and that in cold weather the moisture inside oozes out, freezing as it does so. Some ribbons were as long as 5 or 6 inches. They had in general about the thickness of a cake-knife blade and were from 2 to 2 inches broad.

A Proposed Dimension for Rain-Gage Collectors
By B. C. Kadel

(To be published in Monthly Weather Review.)

Observing Surface Water Temperatures at Sea
By C. F. Brooks

(To be published, with the discussion, in the Monthly Weather Review.)
A Preliminary Study of Effective Rainfall
By J. F. Voorhees

(To be published in Monthly Weather Review.)

Discussion-Mr. J. B. Kincer heartily commended the speaker for undertaking this novel type of investigation and hoped that further work would be done along the same line. He remarked that we exercise the greatest possible care in accurately measuring the total rainfall, but are often little concerned as to the portion of it that is in reality available, i. e., "effective" in crop growth. It is this latter information that is of real interest and value in agricultural meteorology, especially in studies of the relation of rainfall to crop production.

The following papers were read by title:

Windstorm Damage Insurance
By F. L. Hoffman

Franklin's Kite Experiment and Modern Kite Work
By Alexander McAdie

At the conclusion of the scientific program a short business session was held. Upon motion the President of the Society was made, ex-officio, chairman of the Meisinger Aerological Research Fund Committee. The President appointed as other members of this committee, Messrs. R. DeC. Ward, C. F. Marvin, and W. R. Gregg.


The Committee on Resolutions reported as follows:

1. WHEREAS, the meeting of the American Meteorological Society has been facilitated by the arrangements made for it by the Weather Bureau. RESOLVED, that the Society desires to express its appreciation of these arrangements and of the cordial welcome extended to it by the Chief of the Bureau.

2. RESOLVED, that the Society is interested in the matter of long range weather forecasting and desires to encourage all classes of re

search leading to that end and the collection of such observations on the land and water areas of the world as may be needed.

3. RESOLVED, that the Society is interested in the adaptation of the weather forecasts to the needs of specific industries, such as sugar growing, citrus raising, harvesting crops and protection of crops by spraying, so intensively developed during the past few years, and would encourage the extension of this class of forecasts to all industries and activities which are dependent on weather changes.

4. RESOLVED, that the Society is interested in international co-operation in meteorology and expresses its gratification at the formation, under the auspices of the Meteorological Section of the International Union of Geodesy and Geophysics, of an organization for the study of world problems in regard to the atmosphere.

5. RESOLVED, that the Society is interested in the collection and publication of a vocabulary of meteorological terms and hopes that some means may be found to make such a glossary available.

Upon motion, the resolutions were unanimously adopted.

The Society adjourned at 4.30 P. M.

The Secretary's brief summary of the fifth anniversary meeting of the Society appeared in Science on February 13, 1925, pp. 189-190.

A short abstract of the papers presented at the Symposium on Ancient Climates at the meeting of Section E, A. A. A. S., will be published in the BULLETIN after the papers appear in the Scientific Monthly. Several other papers of interest to meteorologists were:


1. The Rainfall Regime as a Great Handicap to Tropical Development, with special mention of Australia-S. S. Visher, University of Indiana, Bloomington, Ind.

2. An example of Local Variations in Tropical Climate-J. Russell Smith, Columbia University, New York.

3. The Dairy Industry of Wisconsin as an Adjustment to the Natural Environment-Glenn T. Trewartha, University of Wisconsin, Madison,



Abstracts are reprinted from Bulletin Ec. Soc. of Am., Dec., 1924 1. The Problems of Phenology and Related Subjects-V. E. Shelford, University of Illinois. (p. 33.)

2. Fluctuations in Atmospheric Pressure and Life-Stanley G. Zinke, Cincinnati, Ohio. (p. 34.)

3. Some Weather Relations of the Pale Western Cutworm-W. C. Cook, Montana Experiment Station. (p. 35.)

4. Measurement of Physical Factors in the Tropical Rain Forest of Panama-W. C. Albee, University of Chicago.


1. Summary of Radiometric Measurements of Planetary_Temperatures W. W. Coblentz, Bureau of Standards, and C. O. Lampland, Lowell Observatory.

2. Further Evidence regarding the Correlation between the Solar Activity and Atmospheric Electricity-Louis A. Bauer, Carnegie Institution of Washington.

« AnteriorContinuar »