摘要:

This paper describes a method of obtaining a permanent record of the vibrations of a tuning fork against a free pendulum. The apparatus consists of a Coast and Geodetic Survey quarter‐second pendulum fitted with special knife edges which are illuminated by a 400‐watt projection lamp. The flashes thus produced fall upon a potassium hydroxide photo‐electric cell. The few micro‐amperes of cell current are amplified by means of a suitable resistance coupled amplifier in order to operate an oscillograph element. This element records its motion on the film of a special high speed camera, giving a record 40 feet in

ISSN:0002-8606    

DOI:10.1029/TR007i001p00053-2

年代:1926

数据来源: WILEY

摘要:

Longitude determinations of a precise nature are made by measuring the difference in longitude between a point of unknown position and a point whose position has been very accurately determined. The longitude difference can as well be expressed as a time difference and is, in fact, so measured, and it is evident that the accuracy with which the time difference is known is the sole factor determining the accuracy of the results of the longitude observations.The modern method of measuring differences in longitude is to compare time as obtained by local star observations with a radio time‐signal sent at a known time from a point of known longitud

ISSN:0002-8606    

DOI:10.1029/TR007i001p00054

年代:1926

数据来源: WILEY

摘要:

At a previous meeting, of this Section, I told you very briefly about some gravity determinations at sea made by Dr. Meinesz, of Holland, Engineer to the Dutch Geodetic Commission. You remember he used an ordinary Stückrath pendulum apparatus, but made his observations in a submerged submarine and recorded the oscillations of the pendulums photographically. In the summer of 1923, on a trip from Holland to Java through the Mediterranean Sea and the Suez Canal, Dr. Meinesz made about thirty gravity determinations at sea with an accuracy much greater than had ever before been attained at sea

ISSN:0002-8606    

DOI:10.1029/TR007i001p00056

年代:1926

数据来源: WILEY

摘要:

For many years geodesy was considered to be a science devoted only to the determination of the shape and size of the earth. In general the operations necessary to make such determinations were base measurements, triangulation, and the determination of astronomic latitudes, longitudes, and azimuths. The first geodetic work of any importance was the triangulation in Lapland and Peru to test Newton's view that the shape of the earth was that of an oblate spheroid. There was also an important piece of geodetic work involved in the extension of the French arc from which the shape and size of the earth were derived in order to establish the metric system.

ISSN:0002-8606    

DOI:10.1029/TR007i001p00058

年代:1926

数据来源: WILEY

摘要:

Lateral, or horizontal, refraction is quite frequently encountered in the angular measurements of triangulation systems, but its occurrence is usually spasmodic and may usually be attributed to air currents or pockets on lines in proximity to buildings, mountain masses, etc. Two cases of consistent lateral refraction have occurred in Canada which permit the underlying causes in these cases to be investigated and, perhaps, explained.An extended and persistent example of lateral refraction was met on the triangulation net of the St. Lawrence River and Gulf, the field work of which covered some 325 miles and extended over four seasons. In this net the lines along the river bank were so consistently “bent” towards the river that a practice had to be adopted of ending observations on these lines only when the results on at least two nights showed a satisfactory agreement. Lateral refraction affecting the observations by from 5 seconds to 15 seconds of are was not at all uncommon, and it has been estimated that almost three times the amount of clear weather ordinarily necessary to secure the required program of observations was used to secure the required accuracy. Even with the precautions which were taken, the evidence shows a regular bending towards the river of the lines parallel to the river. This is evidenced by the error of closure of triangles, the sum of the three observed angles being less than the theoretical sum in the majority of ca

ISSN:0002-8606    

DOI:10.1029/TR007i001p00061

年代:1926

数据来源: WILEY

摘要:

The effects referred to were first observed at the Dominion Observatory, October 11, 1916. They consisted of rhythmic oscillations of a cement pier, following the disconnection, after a long period of equilibrium conditions, of a small electric heater, placed in the underground vault in which the pier in question supported a “Deformation Instrument” or tilt‐measuring seismograph.A series of experiments followed, which continued to December, 1920. A paper describing these was given, by title only, before the American Physical Society and Section B (Physics) of the American Association for the Advancement of Science, at the Chicago meeting, December 28–30, 1920. An abstract of this lecture was given in the Physical Review, vol. XVII , March, 1921, pp. 376–377. A complete account of the work was published as one of the series of Publications of the Dominion Observatory, Ottawa (vol. V, no. 2 ) , with the title, The Effect of Cooling on a Ce

ISSN:0002-8606    

DOI:10.1029/TR007i001p00064

年代:1926

数据来源: WILEY

摘要:

The title of the present paper on which the writer was asked to speak fit this meeting of the American Geophysical Union has undoubtedly aroused in the minds of many the question of the necessity or advisability of new tables for earthquake waves. Why not standardize our results by adopting officially one of the sets of tables now in use instead of adding to the confusion by issuing new ones?

ISSN:0002-8606    

DOI:10.1029/TR007i001p00065

年代:1926

数据来源: WILEY

摘要:

The results of seismological researches are of significance to the student of oceanography in the same way that they are to any other student of general geophysics. Most of the hydrosphere, one of the shells of material which compose the earth, is contained in the ocean basins, which are bounded above by the atmosphere and below by the lithosphere, two other shells of earth substance. If the student of the ocean wishes to understand the relations of the hydrosphere to the other components of the earth he must pay attention to seismology and studies of earth tides, for those are important sources of information on the internal constitution of the earth.

ISSN:0002-8606    

DOI:10.1029/TR007i001p00069

年代:1926

数据来源: WILEY

摘要:

While the isostasist can assist the seismologist in the study of earthquakes, their cause and effect, at the same time the seismologist can be of great assistance to the isostasist.With the proof of isostasy, we are led to believe that the earth's crust must be quite weak in order that the adjustment may be so nearly perfect as has been found.

ISSN:0002-8606    

DOI:10.1029/TR007i001p00072

年代:1926

数据来源: WILEY

摘要:

Since the time of Perrey much statistical study has been devoted to seeking a relation between the frequency of earthquakes and the position of the moon. Different investigators have arrived at contradictory conclusions; so that the results of all this work have been disappointing. I think we shall see the reason for this if we look at the problem from a dynamical standpoint. The earth is tidally distorted by the moon and stresses must be set up which will add to those growing independently in the earth and influence the time of occurrence of a particular earthquake, and a preliminary estimate indicates that this influence may be important. Yet the influence depends not only upon the position of the moon, but also upon the direction of the strike of the fault where the fracture is about to take place with respect to the azimuth of the moon and on the dip of the fault. Of two faults similarly situated with respect to the moon, but with the downthrow on opposite sides of the fault, one will be advanced and the other retarded. In any large catalogue of earthquakes, faults will be involved striking in various directions, with different dips and with downthrown sides both towards and away from the moon. We conclude, therefore, that although the moon may have a definite effect on any particular fault, the hour‐angle for its greatest effect will differ much for different faults, and no hour‐angle will be especially predominant when a long list of earthquakes are studied statistically. This is only a preliminary note on a subject still under investigat

ISSN:0002-8606    

DOI:10.1029/TR007i001p00073

年代:1926

数据来源: WILEY