摘要:

C. W. Horn, National Broadcasting Company, New York, New York—I am very glad to be present and hear these comments on the value of time‐signals, because of the Interest that those of us in the radio game have in accurate standards—all of which are based on accurate time‐measurements. I was interested in listening to the reports of difficulties in checking time in the field and on location, and the demand that was made for more frequent time‐ticks by radio. I am afraid that the broadcasting organizations are not able to furnish such a time‐service unless they supplement the Naval Observatory time‐tick. It may be possible for some stations to do as the Westinghouse station KDKA is doing, that is, send a time‐beat every hour on the hour right through the program.. In the case of Westinghouse, they are using their own clock. In order to make such a service of value to the checkers in the field, these time‐heats must originate at the Naval Observatory, which would require wire‐lines and suitable correction‐apparatus in order to prevent relay‐lag. However, there is quite an expense Involved, which it is feared the broadcasting companies are no

ISSN:0002-8606    

DOI:10.1029/TR012i001p00032

年代:1931

数据来源: WILEY

摘要:

During the past year this project has moved forward, though perhaps not as rapidly as hoped and desired.Of the two quantities to be measured in the determination of gravity, time and length, it is the latter which calls for the most careful preparation and execution, as upon it the precision of the result chiefly depends. The measurement of time can be carried to an accuracy considerably greater than that of length. The best that can probably be hoped for in a measurement of length in a vertical position, as with a reversible pendulum, is one part in a million, and to reach this unusual care will be necessary.

ISSN:0002-8606    

DOI:10.1029/TR012i001p00037

年代:1931

数据来源: WILEY

摘要:

In continuation of the program of gravimetric work ordered by the Department of Geographic and Climatological Research during the year 1930, twelve gravity‐stations were observed, all in the central plain of our Republic, besides the two determinations at the base‐station in Tacubaya. The apparatus used was constructed by the firm of Berger and Sons of Boston, and consists of three invariable bronze pendulums, one‐quarter meter in length and one‐half second in oscillation, besides the thermometer‐ pendulum, coincidence‐ or flash‐apparatus, interferometers, chronometers, etc., similar to those used by the United States Coast and Geodetic Survey, with which differences of gravity between two given places are obtained with great precision. Knowing the value of the intensity of gravity in Tacubaya, which was determined in 1912, with relation to that at Washington, all our observations have been reduced to obtain the differences In gravity between the stations in the field and the known value for the base‐station at Tacubaya. The observations in this last city, made before and after each circuit, were for the purpose of testing the invariability of the mass of the pendulums and, consequently, the periods of oscillation and to correct the field‐values for the resulting small difference. These are found in the “Table of the duration of one oscillation in Tacubaya” and in the curves of the periods of oscillation deduced from the same, which follow at th

ISSN:0002-8606    

DOI:10.1029/TR012i001p00038

年代:1931

数据来源: WILEY

摘要:

The Gravity Committee of the Section of Geodesy made several important decisions at Stockholm, all of which were in due course approved by the Section. (The nameSectionwas later officially changed toAssociation.) These decisions may seem to relate to somewhat technical matters and to concern chiefly those persons who attend to the minute details of the various calculations but they are, in fact, fundamental enough to deserve mention here.

ISSN:0002-8606    

DOI:10.1029/TR012i001p00040

年代:1931

数据来源: WILEY

摘要:

Several years ago the Bureau of Standards purchased a precision circular dividing‐engine and a circle‐testing apparatus. The need of the geodesist for more precise circles for first‐order theodolites was one of the principal reasons for purchasing this equipment as I explained in a paper which I presented before this Union in 1925 (see Transactions, pp. 36–38). Since that time considerable work has been done with this equipment. Much more time was occupied in the preliminaries than had been anticipated. Modifications of both instruments were found necessary and desirable. Circles were then graduated and tested at the Bureau some time later. Although no errors were found in excess of two seconds, and there are indications that the actual errors of graduation were much less than this, field‐measurements using the circles were reported as indicating the presence of much larger errors in the graduation. Although confident that the circles had been graduated with a high degree of accuracy, and that our calibrations of the graduations were also precise, it seemed advisable to wait until something more definite could be stated before making any progress‐report. During the past year, however, enough information has been obtained to warrant a report fi

ISSN:0002-8606    

DOI:10.1029/TR012i001p00043

年代:1931

数据来源: WILEY

摘要:

A study of the influence of the moon's position in the sky upon determinations of astronomical latitude, as exhibited in an analysis of the Gaithersburg and Washington observations, was presented at the Washington meeting of the American Geophysical Union in May 1930 (see Transactions, pp. 148–152). The present paper continues the discussion with additional evidence obtained from studies made at Perkins Observatory of the latitude‐observations obtained at Uklah, California, and longitude‐observations obtained at Washington during the longitude‐campaign of

ISSN:0002-8606    

DOI:10.1029/TR012i001p00045

年代:1931

数据来源: WILEY

摘要:

The establishment astronomically of points at intervals on a theoretical unsurveyed geodetic line is an unusual example of a specialized problem occurring in Canadian survey‐practice. Where the line in question is long and does not form part of a parallel of latitude nor a meridian of longitude, the problem becomes mathematically complex requiring for its precise solution the application of advanced geodesy as well as the science of astronom

ISSN:0002-8606    

DOI:10.1029/TR012i001p00047

年代:1931

数据来源: WILEY

摘要:

Practically all of the field‐work in geodesy in the United States is executed by the United States Coast and Geodetic Survey. That organization is charged by law with extending triangulation‐ and leveling‐nets over the country, making gravity‐surveys in the United States and its outlying areas, and observing the variations of latitude at Ukiah, California, and Gaithersburg, Maryland.In the office of the Coast and Geodetic Survey in Washington, D.C., computations and adjustments of the observations made in the field are carried on; interpretations of the data are made and research in certain geophysical problems are conducted in which the geodetic data are used. The development of instruments for making the field‐observations is also a part of the normal duties of t

ISSN:0002-8606    

DOI:10.1029/TR012i001p00051

年代:1931

数据来源: WILEY

摘要:

The determination of velocities is one of the fundamental objectives of seismological investigations on any scale. Knowledge of the speeds with which energy is propagated as elastic waves in the materials of the Earth is basic to all interpretations of seismological data. In view of this, it is surprising how little seems to have been done in the way of making rigorous determinations of those speeds.

ISSN:0002-8606    

DOI:10.1029/TR012i001p00061

年代:1931

数据来源: WILEY

摘要:

The expanded program for the geodetic work of the United States is of especial importance to seismologists. As is well known, the triangulation and leveling involved in this geodetic program are designed to furnish very accurate geographic positions and elevations. After an earthquake has occurred near an arc of triangulation or line of levels, the field‐observations can be repeated and the extent of the horizontal or vertical movements of the Earth's surface can be determined. It is especially important that we should learn the maximum distance, at right‐angles to the active fault, to which the movements ext

ISSN:0002-8606    

DOI:10.1029/TR012i001p00065

年代:1931

数据来源: WILEY