摘要:

The measurement of the acceleration of gravity over the oceans is a matter of interest to the geodesist in the determination of the figure of the geoid and in investigations relating to isostatic compensation. For the requirements of these problems it is desirable that the probable error of the gravity determinations should not exceed one part in 50,000. At first sight this accuracy does not seem to be unattainable, particularly to those who are familiar with the remarkable work that has been done with invariable pendulums on land stations, where the probable error has been reduced to two or three parts in a million. But when we consider that in measurements at sea the vertical acceleration of the ship is imposed upon the gravitational acceleration which we are trying to measure, the difficulty of the problem becomes apparent. For example, in the case of a ship which rises and falls through a height of a meter during a period of 10 seconds, the average vertical acceleration without regard to sign is about 0.004g, or 200 times the permissible probable error of the measurement. Such vertical accelerations of the ship are not uncommon, although the sea is sometimes so smooth that an index point may be set in grazing contact with the surface of a mercury column with almost laboratory precision.

ISSN:0002-8606    

DOI:10.1029/TR002i001p00003

年代:1921

数据来源: WILEY

摘要:

I assume that I am expected to bring forward whatever ideas will, in my opinion, help most at the present time in the development of a study of isostasy by stimulating further thinking along that line. From among the many topics which might be treated, I am selecting three:(1) I shall make some remarks on the recent paper entitled “The Chemistry of the Earth's Crust,” by H. S. Washington.(2) I shall try to emphasize the desirability of an intensive study of two small areas by observations of gravity and deflections of the vertical.(3) I shall offer some considerations that lead me to believe that the undertow involved in isostatic readjustment is above, rather than below, the depth of compensat

ISSN:0002-8606    

DOI:10.1029/TR002i001p00011

年代:1921

数据来源: WILEY

摘要:

I understood Professor Hayford to say that he did not believe that a fluid layer exists beneath the solid crust of the earth. The same conclusion may be drawn from the earth tide experiment which was conducted on the grounds of Yerkes Observatory by Professor Michelson and myself. It seems pretty certain that the earth tides are the same as they would be if the earth were a highly elastic homogeneous solid, both with respect to the phase and amplitude of the earth tides.The experiment was entirely successful from a physicist's standpoint. The interferometers gave very little trouble. One of them did not require readjustment during the entire year. Two were readjusted to change the width of the fringes, and on one interferometer it was necessary to re‐silver one of the mirrors. As a source of light we used commercial alternating Cooper‐Hewitt lamps, and they proved to be entirely satisfactory. The only serious interruptions were caused by breaks in the electric service due to storms, and occasional short shut‐downs by the electric light company which supplied the current. The experiment at Yerkes Observatory was continued for just one year. This is probably long enough to give values of the semi‐diurnal and diurnal tides, accurate to a few tenths of one percent. For tides of longer period the experiment should be continued for, say, five years, although possibly three years would be long

ISSN:0002-8606    

DOI:10.1029/TR002i001p00016

年代:1921

数据来源: WILEY

摘要:

There is one instrument of use in the study of terrestrial gravity which has not yet been employed in the western hemisphere, though it has to a limited extent in Europe. This instrument is the Eötvös balance. It should be tried, I believe, in making the proposed minute investigation of gravity in a level region of limited extent. To judge by accounts of work done with the balance in Europe it would certainly supplement the pendulum advantageously in the proposed gravity survey and might largely supersede it. This does not by any means signify, however, that the balance is always and everywhere a substitute for the pendulum. This is not the occasion for an exposition of the principles of the instrument, but it may be said that the Eötvös balance connects the results at adjacent points in a limited region with one another in a way that the pendulum cannot well

ISSN:0002-8606    

DOI:10.1029/TR002i001p00017

年代:1921

数据来源: WILEY

摘要:

There are two methods of attacking the problem of the elastic properties of the earth, (1) the study of the seismological evidence, on which I shall not touch at all, and (2) the study of earth tides. Even after the best available observational evidence from the earth tides has been obtained, a good deal of hypothesis and interpretation is required before we can say: “The elastic constants of the earth are thus and so.” It is not, however, of this that I wish to speak, but rather of the problem of obtaining the true values of the earth tides. This subject is connected with several other geophysical questions and this paper, therefore, falls naturally into three divisions: (1) Earth tides and the long‐period oceanic tides; (2) earth tides and the short‐period oceanic tides; (3) earth tides and the variation of l

ISSN:0002-8606    

DOI:10.1029/TR002i001p00018

年代:1921

数据来源: WILEY

摘要:

For more than fifteen years the Astrophysical Observatory of the Smithsonian Institution has been engaged in making measurements of the radiation of the sun. These measurements have indicated that the sun's emission is variable. The Institution now maintains two stations— one in Arizona and the other in Chile—for observing the solar variability. Telegraphic reports of the results obtained in Chile have been forwarded to Buenos Aires and Rio de Janeiro for the use of the meteorological services of Argentina and Bra

ISSN:0002-8606    

DOI:10.1029/TR002i001p00027

年代:1921

数据来源: WILEY

摘要:

My contribution to this discussion is an appeal for a more careful and consistent recognition of the effects and operations of chance in the study of data which may be employed in investigations of solar and terrestrial relations, periodicities, etc. Weather conditions, atmospheric transmission of radiation, magnetic phenomena, sunspots, observed intensities of radiation, and values of like phenomena are subject to large and irregular accidental variations, due account of which must be taken in reaching conclusions.My point of view is illustrated in an admirable manner by figure 1, which serves to show how weak the observational basis still is to justify the claim that there are important irregular changes from day to day in the intensity of solar radiation.

ISSN:0002-8606    

DOI:10.1029/TR002i001p00031

年代:1921

数据来源: WILEY

摘要:

Investigations in the field of general meteorology have been and continue to be restricted and handicapped by the fact that there are not available to investigators daily charts of the world's weather. It is necessary in investigations in meteorology and particularly in weather forecasting that problems now but imperfectly understood be considered from a world‐wide viewpoint, for there can be no doubt that much that we call “weather” is not of local origin, but has its inception in the general actions and reactions that involve at times the atmosphere over an entire hemisphere and possibly both hemispheres. Hence, investigation based on a study of daily synoptic charts for a limited area, such as Europe, the United States of North America, or of India, can lead to but an imperfect understanding of the general physical processes that are in operation to produce our day‐to‐day weather. Moreover, when it is understood how rapid are the changes in speed, direction of movement and magnitude of areas of high and low barometric pressure, there arises the natural desire to look into the observable facts over a world‐wide area in an attempt to determine the causes of them. Meteorology without a world‐wide weather map is laboring under difficulties as great, or greater, without realizing it, than astronomy without its star charts. Hence it is contended that many of the important problems of meteorology will not and cannot be solved until there be available daily synoptic charts of the various meteorological elements of, relatively speaking, the entire world. It would redound to our credit if the American Geophysical Union should become instrumental in bringi

ISSN:0002-8606    

DOI:10.1029/TR002i001p00036

年代:1921

数据来源: WILEY

摘要:

Aerology may be very simply defined as “the study of the free air”; world aerology, as an extension of that study to all parts of the world. By this we mean not only the continental areas, but the seas as well; and not merely sections of a hemisphere, but from pole to pole. It is our purpose to review very briefly (1) what has been and what is being done toward this end; (2) more particularly, to outline whatcan at onceand also whatshouldlater from time to time be underta

ISSN:0002-8606    

DOI:10.1029/TR002i001p00041

年代:1921

数据来源: WILEY

摘要:

Meteorological data are gathered for, and serve, many purposes:They are abundantly used in forecasting the weather of the morrow, but obviously used only once, and hence for this purpose need not be recorded.They also are collected in the course of special studies, but the completion of each investigation renders useless the preservation of the particular material treated. It is the generalization—the law—that counts, and not the isolated values from which it happened to be dedu

ISSN:0002-8606    

DOI:10.1029/TR002i001p00049

年代:1921

数据来源: WILEY