摘要:

The American Geophysical Union is the American National Committee of the International Geodetic and Geophysical Union, and the Executive Committee of the American Geophysical Union is the Committee on Geophysics of the National Research Council. The object of the Union is to promote the study of problems concerned with the figure and physics of the Earth, to initiate and coordinate researches which depend upon international and national cooperation, and to provide for their scientific discussion and publication. In the accomplishment of this object, the Union is divided into sections following the plan of organization of the International Geodetic and Geophysical Union. Originally there were seven sections, namely, (a) Geodesy, (b) Seismology, (c) Meteorology, (d) Terrestrial Magnetism and Electricity, (e) Oceanography, (f) Volcanology, and (g) Geophysical Chemistry. The Section of Geophysical Chemistry was discontinued May 31, 1924, as the International Union had failed to provide such a section. At the meeting in May 1930 of the American Geophysical Union, a Section of Hydrology (g) was authorized to conform to the Section of Scientific Hydrology of the International Union. (Matters pertaining to scientific hydrology referred to the American Geophysical Union had been previously looked after by special committees on hydrology.)

ISSN:0002-8606    

DOI:10.1029/TR010i001p00007

年代:1929

数据来源: WILEY

摘要:

Observations of gravity were made at 18 stations in Mexico between January 1, 1926 and December 31, 1928. (The positions of the stations and the values of gravity obtained during this period are included in the table accompanying the report submitted May 1930 by Dr. Sanchez to the Section of Geodesy as published in this Volume; descriptions of the gravity‐stations will be found in the “Memorias annuales del Departamento Geográfico de Campo” of the Dirección de Estudios Geográficos y Climato

ISSN:0002-8606    

DOI:10.1029/TR010i001p00017

年代:1929

数据来源: WILEY

摘要:

For the purpose of obtaining a direct gravity‐connection between Ottawa and European base‐stations the Dominion Observatory made, during the summer of 1928, relative determinations of gravity at Ottawa, Greenwich, and Potsdam. Ottawa is the base for some 100 field stations in different parts of Canada. Greenwich is a recognized base‐station for gravity‐work in Great Britain, India, and the Dominions. Potsdam is the base to which gravity‐stations in all countries throughout the world are referred. Potsdam is also one of the limited number (possibly two) of places at which a strictly accurate absolute determination of gravity has been made. In addition to making possible a comparison between Canadian gravity‐stations and other gravity‐determinations throughout the world the work is of interest at the present time in view of its bearing on the question of the reality of the longitude‐term in the formula for gravity. The value of the comparisons was increased by a connection that was made early this year between Ottawa and Washington. Potsdam, Greenwich, Ottawa, and Washington are therefore linked together by t

ISSN:0002-8606    

DOI:10.1029/TR010i001p00020

年代:1929

数据来源: WILEY

摘要:

Many attempts have been made to devise a satisfactory method for the measurement of gravity over ocean‐areas. These methods have been chiefly of the elastic‐deformation type in which the weight of a mass has been balanced either by an elastic solid or by a gas. None of these methods has thus far proved satisfactory either because of elastic hysteresis, or because of inadequate temperature‐control, or of other defects in the apparatus. Hecker sought to measure gravity by another method, namely, by comparing the height of the mercury‐column in a barometer with the barometric pressure determined from the boiling‐point of water; but this method failed to give results of the desired

ISSN:0002-8606    

DOI:10.1029/TR010i001p00022

年代:1929

数据来源: WILEY

摘要:

The Naval Observatory time‐service has undergone in recent years an interesting development and expansion. This has been brought about by a demand for increased accuracy in the time‐signals. The task of sending regular signals of sufficient accuracy to meet the needs of navigation and every‐day life is, of course, relatively simple. When, however, the signals are to be used by longitude‐parties and radio laboratories and are to be subjected to comparison with similar signals emanating from foreign observatories, the highest obtainable degree of accuracy becomes de

ISSN:0002-8606    

DOI:10.1029/TR010i001p00023

年代:1929

数据来源: WILEY

摘要:

During the past two years there have been a number of improvements and new instruments developed by the United States Coast and Geodetic Survey in its geodetic instrumental equipment. The principal matters, to be mentioned are the completion of a first‐order theodolite, the development of a second‐order instrument of the sane nature, and the improvement in the design and method of graduation of the precise level

ISSN:0002-8606    

DOI:10.1029/TR010i001p00026

年代:1929

数据来源: WILEY

摘要:

Ottawa, Ontario, “the Washington of the North,” being the seat of the Federal Government, is the headquarters of the Geodetic Survey of Canada and is situated at the point where the Rideau River joins the Ottawa; a very picturesque sight both from a natural and artistic standpo

ISSN:0002-8606    

DOI:10.1029/TR010i001p00028

年代:1929

数据来源: WILEY

摘要:

Since last year's meeting of the Section the usual computations have been carried forward by the United States Coast and Geodetic Survey in triangulation, leveling, geodetic astronomy, and gravity.

ISSN:0002-8606    

DOI:10.1029/TR010i001p00035

年代:1929

数据来源: WILEY

摘要:

With few exceptions the field geodetic work in the United States is carried on by the United States Coast and Geodetic Survey. This has been the case for a number of years, especially since the Survey has been able to carry on all of the work for which it has been given funds. Of course, the operations of the Survey could be greatly extended if the government officials should feel that greater activity in field geodesy were desirable.

ISSN:0002-8606    

DOI:10.1029/TR010i001p00036

年代:1929

数据来源: WILEY

摘要:

Before the time of Lord Rayleigh the mathematical theory of elasticity did not provide any theoretical basis for the existence of surface‐waves in an elastic solid. Consequently, attempts were made to explain the so‐called principal or main phase in the earthquake records by reflection, scattering and interference of body‐waves. Such hypotheses failed to account for the difference of velocity between these waves and the body‐waves and for the fact that the travel time of the main phase was observed to be approximately proportional to the distance of the observing station from the epicenter of the earthquake. In 1887 Rayleigh published in the Proceedings of the Mathematical Society of London a communication on “Waves propagated along the surface of an elastic solid” in which he presented a theory which was further developed by Lamp in 1904. These waves have since been designated Rayleigh waves. According to the theory the energy of the wave dies out rapidly with distance from the surface. The particles vibrate in elliptical paths whose major axes are perpendicular to the surface and whose minor axes lie parallel to the direction of propagation of the wave. The ratio of the vertical to the horizontal amplitude is nearly one and one‐half. The velocity of Rayleigh waves is less than that of true shear waves in the same medium. The ratio of velocities is approximately ninety

ISSN:0002-8606    

DOI:10.1029/TR010i001p00041

年代:1929

数据来源: WILEY