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BULLETIN OF THE NATIONAL RESEARCH February, 1931 PHYSICS OF TIlE EARTH II THE FIG URE OF THE EAR'1'I] A COLLECTION COUNCIL Number 78 OF SHORT PAPERS, WRITTEN BY LEADING SCIENTIFIC MEN IN SEVERAL BRANCHES OF GEOPHYSICS, AND TREATING OF THE SIZE AND SHAPE OF THE EARTH This report was prepared under the auspices of the National Research Council Committee on Physics of the Earth by the members of the following subcom- mittees of the Subsidiary Committee on the :Fi~,ure of the Earth: Subsidiary Committee on the Figure of the Earth. Fred E. V/right Chairman; illiam Bowie, Vice-Chairmon. Subcommittee on Tides! Ocean and Earth. G. T. Rude, Chairman; A. T. Doodsion, W. D. Lambert. H. A. Marmer, Paul Schureman. Subcommittee on Gravity, Deflection of the Vertical, and Isostasy. William Bowie, Chairman; H. G. Avers, Donald C. Barton, Lyman J. Briggs, W. D. Lambert, Andrew C. Lawson, C. X. Leith, D. L. Parkhurst, Clarence H. Swick, Fred E. Wright. Subcommittee on Variation of Latitude. Frank Schlesinger, Chairman; E. W. Brown, NV. D. Lambert. The Division of Physical Sciences, the Division of Geology and Geog r aphy and the American Geophysical Union also cooperated in pi eparing this report. PUE3~:EST-TED BY TI[E NATIONAl, RESEAR.CTI COUNCIL OF TI~IE ~ ~TI:ON-~\E AC EDEMA OF SCIENCES TVASO:rN-GTON-, D. C. 1931
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i FOREWORD be given to research It is generally agreed that Snore attention should ~ in the middle grouted between the Sciences. Geophysics the study by physical methods of the planet of which we live is a conspicuous instance of such ~ middle-~rouncl science, since it shades offs: imperceptibly in one or other direction into the fields of physics, astronomy, geology, to say ~ othin~ of biolo~,y, with wit ch the sub ject of oceanography is closely connectecl. Some branches of geophysics, such as meteorology, terrestrial magnetism, geodesy and oceanography have long had a more or less independent existence, but it leas become increasingly clear that these subjects, and many others, are all parts of geophysics. For various reasons, among which may be mentioned the development of geophysical methods in prospecting, for oil and ~i~erals, there has lately been ~ con- siderable development calf interest in geophysics, but this development has not been snatched lay the publication in English of systematic treatises on the subject. With these ideas ill mind, Dr. J. S. Antes, during, his term as Chairman of the Division o-E Physical Sciences of the National Research Council, was instrumental in organizing, in 1926 a large committee to prepare a series of Bulletins on The Physics of the Earth, the purpose being " to give to the reader, presumably a scientist but not a specialist in Else subject, an idea of its preselect status together with a Torward- lool~ing sun nary ol- its outstancliną, prol~le~s." In clue course sul~-com~ittees were :for~necl to prepare reports on the following subjects: The Fi~urc of the Earth : Gravity, Deflection of the Vertical and Isostasy Tides, Ocean. and Earth Variation of Latitude Seismology: Terrestrial Magnetism The Age of the Edith Field Methods for Det.ec tiny Unhomogeneitie~ in the Earth's Crust Internal Constitution of the Earthly Meteorology Oceanography Volcanology That this project, as ambitious as it is important, is now coming to fruition with the pul)lication of these Bulletins is due partly to the skill and farsightedness with which Dr. Ames selected the committee and . . .
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1V FORE WORD assisted in outlining its program; partly to the care and interest with which Dr. Ames' successor, Professor Dayton C. Miller, directed the comn~ittee's activities during his terns as Chairman of' the Division; and. particularly to the devotion with which the Chairmen and, members of the several sub-con~mittees have carried out their respective a.ssią,nn~ents. The hearty thanks of:' the National Research Council ancl of the readers of these Bulletins is due to the several authors for their e-tI'orts. The volumes will appear serially in the Bulletin Series of' the National Research Council, with no particular regard cas to sequence, each-volume being issued when ready.