摘要:

Exhaustive field tests and study have been made during the past two years of a 3¾‐inch transit (see Figure 1). This small instrument, 12¾ pounds, is capable of measuring angles with primary accuracy when used within the limits of its telescope‐power, maintains its adjustments under exceptionally strenuous conditions and can be manipulated in about one‐half the time occupied with twelve‐inch, three‐micromet

ISSN:0002-8606    

DOI:10.1029/TR008i001p00044

年代:1927

数据来源: WILEY

摘要:

The world longitude‐campaign by the use of radio signals, which was originally proposed by General Ferrié in 1919, was carried out in 1926. For several years the matter had received the attention of a mixed commission representing the International Astronomical Union and the International Geodetic and Geophysical Union. In its final form the plan called for the simultaneous determination of the longitudes of twenty‐three stations of the first order, representing thirteen countries, and of as many, or more, secondary stations (see Figure 1). Those of the first order comprise the original round‐the‐world‐polygon composed of San Diego, Algiers, and Shanghai, and the stations at Washington, Ottawa, Vancouver, Greenwich, Edinburgh, Paris, Madrid, San Fernando, Naples, Genoa, Mogadiscio, Dehra Dun, Tokyo, Melbourne, Sydney, Adelaide, Wellington, Lembang, Manila, and Honolulu. It was desired to determine the longitudes of these stations with the highest precision possible, both as a contribution to our knowledge of longitudes, and as a basis for future studies relating to possible crustal movements of the Earth's surface. In order that there might be sufficient material even if weather or radio conditions should be adverse, the plan called for work extending over a period of

ISSN:0002-8606    

DOI:10.1029/TR008i001p00050

年代:1927

数据来源: WILEY

摘要:

It was stated at a meeting of this Section two years ago that the first‐order leveling seemed to be developing the fact that the planes of mean sea‐level at adjacent tidal stations along the same coast are not, necessarily, in the same level surface.This condition was first brought to our attention when the tidal stations at Fort Hamilton, New York, and Portland, Maine, were connected by a line of first‐order leveling. The results of the leveling showed the plane of mean sea‐level at Portland to be 169 millimeters higher than the same plane at Fort Hamilton. Similarly, on the Pacific Coast the leveling showed that the plane of mean sea‐level at Vancouver, B.C., was 103 millimeters higher than the same plane at Seattle, Washington. In each case, mean sea‐level at the northern station was

ISSN:0002-8606    

DOI:10.1029/TR008i001p00056

年代:1927

数据来源: WILEY

摘要:

Two stations of the world longitude‐net, Honolulu and Manila, were occupied by observers of the U.S. Coast and Geodetic Survey. Satisfactory observations were obtained at both stations, although at Manila there was some delay in getting started owing to difficulties with the radio apparatus. An interesting feature of the wrork at both stations was the use of the gravity‐pendulum in place of an accurate astronomical cl

ISSN:0002-8606    

DOI:10.1029/TR008i001p00058

年代:1927

数据来源: WILEY

摘要:

At the meeting of this section of the Union last year a partial report on the readjustment of the first‐order triangulation in the western part of the United States was given. The work of the adjustment has now been advanced to the point at which some interesting and important results can be give

ISSN:0002-8606    

DOI:10.1029/TR008i001p00062

年代:1927

数据来源: WILEY

摘要:

Since the last meeting of the Section one major arc of first‐order triangulation has been completed, a minor arc has been begun and completed, and a beginning has been made upon another major arc.The major arc completed was the west end of the 49th parallel, an unusually difficult piece of work; the stations were so inaccessible that five observing parties were used in order to finish the work before the glaciers below the stations should become dangerous. Even with that number of parties, smoke from forest‐fires again so delayed the observing that the stations were finished only with the greatest difficulty and with frequent risk of serious injury to the observers and their assista

ISSN:0002-8606    

DOI:10.1029/TR008i001p00065

年代:1927

数据来源: WILEY

摘要:

In the location of mineral deposits or geological subsurface structures by means of gravity‐measurements, the Eötvös torsion balance has hitherto been used almost exclusively. Pendulum measurements have been but little used in the solution of such problems and then chiefly when the problem was one of surveying large buried tectonic units, extending over a considerable area. What has hampered the use of the pendulum measurements in most cases has apparently been the time required to make them, apart from the fact that the gravity anomalies produced by most types of subsurfaced structures do not greatly exceed the errors of the resu

ISSN:0002-8606    

DOI:10.1029/TR008i001p00066

年代:1927

数据来源: WILEY

摘要:

The activity of the Carnegie Institution of Washington in the field of seismology in 1926 may be reviewed briefly somewhat as follows:One major task, jointly elaborated at the outset between the Institution and the U.S. Coast and Geodetic Survey, contemplated fixing the position both in horizontal and vertical dimensions of significant landmarks throughout the entire zone of earth‐movement in California. The obvious purpose, which has often been alluded to before, was twofold, (1) to fix with precision the actual displacements occurring during earthquakes, (2) the much more novel, and, eventually, perhaps more useful, purpose of attempting to evaluate indications of accumulating stress or “cre

ISSN:0002-8606    

DOI:10.1029/TR008i001p00072

年代:1927

数据来源: WILEY

摘要:

The Jesuit Seismological Association, organized in the summer of 1925, is composed of twelve seismographic stations built and equipped by Jesuit universities and colleges in the United States.

ISSN:0002-8606    

DOI:10.1029/TR008i001p00074

年代:1927

数据来源: WILEY

摘要:

The U.S. Coast and Geodetic Survey has been operating six seismological stations: San Juan, Porto Rico; Cheltenham, Maryland; Chicago, Illinois (at the University of Chicago, formerly operated by the U.S. Weather Bureau) ; Tucson, Arizona; Sitka, Alaska; and Honolulu, Territory of Hawaii (station formerly at magnetic observatory has been removed to the University of Hawaii where it is operated as a cooperative station). A Wood‐Anderson torsion seismometer of the teleseismic type has been in operation at Tucson for a year and we are now able to appraise the results. There are Milne‐Shaw seismographs at Chicago and Honolulu and recently the recording apparatuses have been rebuilt so that the time‐recording is greatly improved. At the other observatories there are obsolete instruments, the Bosch‐Omori, giving good records of .severe earthquakes but missing practically all others. Replacements at Sitka and Porto Rico are part of the program as these are seismic regions of great importance without first‐class instruments anywhere. Replacement at Cheltenham is not contemplated at present, since it is but a short distance from the first‐class station at Georgetown. Probably the operation of seismographs at Cheltenham, except continuation of the Bosch‐Omori, will be for experime

ISSN:0002-8606    

DOI:10.1029/TR008i001p00077

年代:1927

数据来源: WILEY