Terrestrial Magnetism Research Articles

SUMMARY OF DISCUSSION OF MINERAL AGE MEASUREMENTS IN THE CANADIAN SHIELD

Annals of the New York Academy of SciencesVolume 91, Issue 2 p. 430-430 SUMMARY OF DISCUSSION OF MINERAL AGE MEASUREMENTS IN THE CANADIAN SHIELD L. T. Aldrich, L. T. Aldrich Department of Terrestrial Magnetism and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C.Search for more papers by this authorG. L. Davis, G. L. Davis Department of Terrestrial Magnetism and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C.Search for more papers by this author L. T. Aldrich, L. T. Aldrich Department of Terrestrial Magnetism and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C.Search for more papers by this authorG. L. Davis, G. L. Davis Department of Terrestrial Magnetism and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C.Search for more papers by this author First published: April 1961 https://doi.org/10.1111/j.1749-6632.1961.tb35494.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume91, Issue2Geochronology of Rock SystemsApril 1961Pages 430-430 RelatedInformation

British Physics Awards

In Britain, the Council of the recently amalgamated Institute of Physics and Physical Society has announced that it has made three awards, one of which has been received by an American physicist. Scott E. Forbush, mathematical physicist on the staff of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, was named to receive the Charles Chree Medal and Prize for distinguished contributions in the study of cosmic radiation. The other award winners are J. B. Adams, director‐general of the European Organization for Nuclear Research, who has been given the Duddell Medal for his leadership of the CERN team, and A. W. Merrison, professor of experimental physics in the Nuclear Physics Research Laboratory of the University of Liverpool, who received the Charles Vernon Boys Prize for distinguished research in experimental physics.

Dr. William Gilbert — England's First Great Scientist

THERE is no more famous book in the history of science than William Gilbert's De Magnete (On the Magnet), published in London in 1600. It is usually called the first great scientific work written by an Englishman, and remains one of the world's masterpieces. It was the first accurate and comprehensive investigation of terrestrial magnetism — so thorough that little of consequence was added in the next two hundred years. Professors point to it as one of the first and greatest models of inductive experimentation, preceding Galileo, Kepler and Harvey. Like many classics it is more often pointed to . . .

Redetermination of coil constant of sine galvanometer No. 1

Sine galvanometer No. 1 (SGl) was constructed by the Department of Terrestrial Magnetism, Carnegie Institution of Washington, as a primary standard for the determination of the horizontal component of the earth's magnetic field (H). The precision coil for the SGl consists of 40 turns of copper wire wound on a marble form in such a way that 20 turn-pairs can be identified which have the Helmholtz configuration with approximately 300-mm diameters and 150-mm axial spacings. The coil was first measured by Barnett [1921]. Since that time it has gained some importance as an international standard in the determination of H. Because of the importance of the SGl as an international standard, the coil constant was recently redetermined. The new results are compared with the old in Table 1.

Evaluation of average crustal characteristics from reverberation of seismic waves

The seismic records obtained near the shot points during the study of the earth’s crust by the Department of Terrestrial Magnetism, Carnegie Institution of Washington, have been analyzed to investigate the possible origin of the reverberation of seismic waves. The hypothesis of layers of uniform velocities fails to explain the reverberation curves in different regions. As a first approximation, the average gradient of velocity with the depth can be determined and it agrees with the travel-time data provided one assumes the major contribution to be from the conversion of P waves into S waves at the surface irregularities. The average gradient in Virginia, U.S.A., is seen to be 0·075 km s -1 km -1 . When the travel-time curves are investigated on the basis of such a large velocity gradient, the penetration corresponding to rays causing intense arrivals usually associated with the critical reflexions from the Mohorovicic discontinuity comes out to be only 14 km in Virginia, U.S.A. The intense arrivals have to be ascribed now to the focusing effect of peculiar variation in the velocity at about this depth. For example, if sediments extend to a thickness just short of 14 km , the velocity might increase at the base of the sediments to a value greater than the velocity in the upper layers of the converted crustal rock during the formation of the continents. This will give rise to both a low velocity layer and focusing when the velocity again increases at depths somewhat greater than 14 km . On the basis of the ray theory and assuming uniform increase of velocity with the depth, expressions have been derived for the reverberation curves for various kinds of single scattering and the average gradient has been determined for various regions. A mathematical theory for the variation of gradient from a high value at the surface to a negligible value when velocities greater than 8·8 km/s or so are reached would be a logical next step.

Union, section, and committee activities

This Symposium was arranged by W. O, Roberts and held in the Great Hall of the National Academy of Sciences on the afternoon of May 4, 1959. The session opened at 14h 00m and adjourned at 17h 00m.The Symposium consisted of two organized discussions on highly speculative subjects, which stimulated informal debate. The first, on “Solar and Other Cosmic Influences on Planetary Weather and Ionospheres,” was introduced by Seymour Hess (Florida State University), and included discussions principally of Mars, Venus, and Jupiter atmospheric phenomena. Invited comments were presented by Albert G. Wilson (Rand Corporation), Roger Gallet (National Bureau of Standards), William M. Sinton (Lowell Observatory), and B. F. Burke (Carnegie Institute Washington, Department of Terrestrial Magnetism). The first discussion was attended by approximately 180.

On the velocity field of the nearby interstellar hydrogen.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the velocity field of the nearby interstellar hydrogen. Helfer, H. L. Abstract This is a progress report upon the analysis of the 21-cm survey for (b >200, undertaken at the Department of Terrestrial Magnetism, Carnegie Institute of Washington, and reported upon previously (Erickson, HeIfer and Tatel 1959). Rough agreement between Shain's local magnetic pole of the Galaxy (Shain 1957) and the crudely defined pole of the high-latitude interstellar hydrogen suggests that the distribution of the interstellar gas is quite dependent upon the local magnetic field and that the possibility that the velocity-distance relation for the gas is different from that of the stars cannot be ignored. As reported previously, the high latitude 21-cm line profiles give evidence of significant large-scale structure. Accordingly, a solution for the velocity-distance relation of the nearby gas was attempted. Including only first order terms one may write for the radial velocity: V(1, b) = a + sR, where R is the distance and s = K + cos2 b (C + B1 sin 21 + B2 cos 21) + (A3 sin 1 + A2 cos 1) sin 2b, a = W1 cos 1 cos b + W2 sin 1 cos b + W3 sin b. Using subjective estimates of the peak or center of line-profile velocities, solutions for the relative ratios, K: C: B1: B2: A1 : A2, were determined from the seven available values of (1, b) for which V(1, b) + V(1 + 1800, -b) = 0. The preliminary values are: 1.000, -0.820, -0.311,0.182, +0.743, -0.322, in the order given above. The figures quoted are probably already influenced slightly by the occurrence of second order terms, their influence being evident in the observations taken at b = ~ 200. The values of W1, W2, W3, determined from the value of V(1, b) - V(1 + 1800, -b) at the aforementioned zero points, are found to be 1.24 km/sec, 2.62 km/sec, - I .6o km/sec, respectively, but these values are quite crude. If accepted literally, this would suggest that the circular velocity of the local gas is about 3 km/sec faster than that of the stars. The coordinate system used is that defined by the Lund Tables (Ohlsson, Reiz and Torgard 1956) with galactic center at 1 3270, b - 10 and the velocity scale origin is the local stellar standard of rest, as given by the Lund Tables (MacRae and Westerhout 1956). This work was supported in part by the U.S. Air Force under Contract No. AF49(638)-52. REFERENCES Erickson, W. C., Heifer, H. L. and Tatel, H. E. 1959, URSI-IA U Radio Astron. Symp. Paris 1958, in press. MacRae, D. A. and Westerhout, G. 1956, Tables for the Reduction of Velocities to the Local Standard of Rest, Lund Observatory. Ohisson, J., Reiz, A. and Torg~d, I. 1956, Tables for the Conversion of Galactic into Equatorial Coordinates, Lund Observatory. Shain, G. A. 1957, Russian A. J. 34, 3. Department of Physics and Astronomy, University of Rochester, Rochester, N. V. Publication: The Astronomical Journal Pub Date: 1959 DOI: 10.1086/107982 Bibcode: 1959AJ.....64Q.128H full text sources ADS |

Distortion of a Toroidal Field by Convection

In a perfectly conducting body the lines of magnetic force move with the material; the total number crossing the surface in either direction is therefore constant, and cannot be changed by motions of the material forming the body. Both in terrestrial magnetism and in sunspots, large changes in the external field are observed which do involve a change in the total number of lines and cannot be explained by a mere crowding together of lines of force that already cross the surface. In these phenomena loops of field must emerge through the surface, and the theory must involve the finite conductivity of the material.

Recent astronomical tests of thin-film image converters.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Recent astronomical tests of thin-film image converters. Baum, W. A. ; Ford, W. Kent, Jr. ; Hall, John S. Abstract During the past three years the astronomical practicability of a special type of electronic image converter tube has been explored. This tube operates essentially by A. Lallemand's method (i.e., electrons ejected from a photo- cathode are accelerated and focused directly onto a nuclear-track emulsion) but a very thin barrier film or membrane has been added to prevent gas molecules exuded by the emulsion from reaching the photocathode and poisoning it. Electrons of several kilovolts energy can pass through this film but gas molecules cannot. Attention has been confined to designs which are potentially capable of being produced commercially, because the ultimate value of any technique in this field will depend upon its general availability to observatories everywhere. In August and November, 1957, a number of electron-produced images on Ilford G~ plates were obtained at the ~o-inch telescope of the Naval Observatory at Flagstaff, Arizona. The useful field of the Farnsworth tubes under test has a diameter of about iS mm, which corresponds to 9 minutes of arc at the focus of the telescope. The components of double stars were separated on the plate when the distance between their centers was 170 microns; this corresponds to an angular separation of 5 seconds of arc. It is important that the gap between the barrier film and the G~ emulsion should be very small so that the scattering of the photoelectrons by the barrier film will not result in a serious loss of image resolution. A gap of 40 microns has been successfully used at the telescope but attempts in the laboratory to improve the resolution by bringing the film into actual contact with the G~ emulsion by means of electrostatic deflection have given promising results. A number of 3o-second exposures were made on M36 with a tube of low sensitivity and compared with direct photographs of M36 secured on Io3a-D emulsions. Microphotometer tracings indicated that the signal-to-noise performance with the image tube was roughly on a par with that obtained by short-exposure photography. The same image density would have been obtained in a one-second exposure if the cathode of the image tube had been of average sensitivity. In order to avoid excessive background emission, the cathode of the image tube was cooled and accelerating potentials of io kv or less were used. Minor changes in tube design and more efficient cooling should permit the observer to extend the useful exposure time well beyond 30 seconds. The Formvar-aluminum barrier films used in this application had a total thickness of 7ooA. Ford has made a study of the physical properties of self-supported films and has succeeded in making films which will withstand the high temperatures required in image-tube processing and which are strong, fiat, uniform, and free of pinholes. The two tubes used in these experiments were operated for three days without substantial loss in sensitivity. Mount Wslson and Palomar Observatories, Pasadena, Calf. and Department of Terrestrial Magnetism, Carnegie Institution of Washington and U. 8. Naval Observatory, Washington, D. C. Publication: The Astronomical Journal Pub Date: February 1958 DOI: 10.1086/107680 Bibcode: 1958AJ.....63...47B full text sources ADS |

Reviews and abstracts

X, T. Aldrich (Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, D. C.) The Measurement and Applications gf Mimed Ages Modern measurements of radioactive Ims of rocks using the decay of U‐Pb, Th‐Pb, Rb‐Sr, and K‐A have shown that the latter two usually give accurate absolute ages on micas from granites and pegmatites. The ubiquitous occurrence of mica extends the number of sedimentary formations whose ages can be bracketed by common igneous rock. The possibilities for measurements of the age of minerals in these formations are hopeful.Measurements made while testing the Rb‐Sr and K‐A methods have already shown conclusively that geobgic formations older than 2500 m y exist in North America, South Africa, and Australia. It has also ken found that at least 11 Precambrian granites and pegmatites in western United States have values for their ages close to 1350 m y, indicating widespread formation of rocks at that time.

Outer galactic structure from O, B, carbon stars, and neutral hydrogen.

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Outer galactic structure from O, B, carbon stars, and neutral hydrogen. Franklin, K. L. Abstract A comparison is made between observed direction-velocity data for 21-cm radiation of neutral hydrogen, and similar data for 0 and B stars. The 21-cm observations are taken from recent Dutch sources, and from work in the Carnegie Institution of Washington, Department of Terrestrial Magnetism. The stellar data are obtained from R. E. Wilson's catalogue of radial velocities. Within the completeness of Wilson's catalogue, it is shown that the early stars do not necessarily share the positions and velocities of the observed hydrogen. The conclusion by the Case workers that carbon stars are members of the spiral arm population is supported in part by the 21-cm observations. Carnegie Institution of Washington, Washington, D. C. Publication: The Astronomical Journal Pub Date: 1957 DOI: 10.1086/107609 Bibcode: 1957AJ.....62R..15F full text sources ADS |

John Adam Fleming, 1877-1956

On July 29, 1956, quite suddenly as a result of a heart attack, the remarkably active and fruitful career of Dr. John Adam Fleming, the retired director of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, came to an end at San Mateo, California. The Journal of Geophysical Research, the continuation of “Terrestrial Magnetism and Atmospheric Electricity,” esteems it a privilege to honor the memory of Dr. Fleming, its former able editor from 1928–1948 and subsequently its honorary editor.

Scattering of Alpha Particles from Helium

Excitation curves and angular distributions for the scattering of $\ensuremath{\alpha}$ particles from helium have been obtained for bombarding energies of 3 to 6 Mev, using a differentially pumped gas scattering chamber and a singly charged $\ensuremath{\alpha}$-particle beam from the Rice Institute Van de Graaff accelerator. A phase shift analysis of the data, yielding phase shifts accurate to about 2\ifmmode^\circ\else\textdegree\fi{}, reveals that only $S$- and $D$-wave scattering occurs and shows that the well-known excited state at 2.9 Mev in ${\mathrm{Be}}^{8}$ is a $D$ state. The scattering data taken at the Department of Terrestrial Magnetism and the Universities of Illinois and Indiana are compared to the Rice Institute data by using the dispersion theory and the Landau $K$-function formalism developed for proton-proton scattering. The dispersion theory, applied to the Rice data, allows a rough estimate of the $D$-state level parameters, while the $K$ function, applied to the Rice and D.T.M. data, is used to deduce a ground state width for ${\mathrm{Be}}^{8}$ of 4.5\ifmmode\pm\else\textpm\fi{}3 ev (c.m.). For excitation energies below 12 Mev, the scattering data are consistent with a description of the ${\mathrm{Be}}^{8}$ nucleus as an interaction of two $\ensuremath{\alpha}$-particles. Certain qualitative features of the potential of interaction of such a two-body configuration are discussed.

John A. Fleming

John A. Fleming, retired director of the department of terrestrial magnetism at the Carnegie Institution of Washington, died on July 29 at the age of 79.

Bibliography on the history of terrestrial magnetism

Bibliography on the history of terrestrial magnetism

Cosmic Rays in the Terrestrial Magnetic Dipole Field

The results of scale model experiments with electron orbits in a magnetic dipole field are given in the form of diagrams on big globes. By using these globes it is possible to find the asymptotic directions of cosmic ray particle orbits as a function of momentum and direction of incidence at a cosmic ray recording station. Globes, representing 16 stations are depicted. DOI: 10.1111/j.2153-3490.1956.tb01214.x

Precancer cells in amphibian adenocarcinoma.

Annals of the New York Academy of SciencesVolume 63, Issue 6 p. 1280-1302 PRECANCER CELLS IN AMPHIBIAN ADENOCARCINOMA William R. Duryee, William R. Duryee Carnegie Institution of Washington, Washington, D. C.Search for more papers by this author William R. Duryee, William R. Duryee Carnegie Institution of Washington, Washington, D. C.Search for more papers by this author First published: March 1956 https://doi.org/10.1111/j.1749-6632.1956.tb32137.xCitations: 46 The research described in this paper was carried on while the author was a member of the staff of the National Cancer Institute, Bethesda, Md., between 1950 and 1955, while he was assigned to the Biophysics Section of the Carnegie Institution's Department of Terrestrial Magnetism. Grateful acknowledgment for the support and facilities provided is hereby made. Department of Physiology, George Washington University, School of Medicine, Washington, D. C. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume63, Issue6Cancer Cytology and CytochemistryMarch 1956Pages 1280-1302 RelatedInformation

Union, section, and committee activities

A Committee was appointed by the President of the Section of Terrestrial Magnetism and Electricity to consider other names for the Section and to make recommendations. The report of the Committee is as follows: The Committee appointed to recommend a name for the Section of Terrestrial Magnetism and Electricity has unanimously agreed to recommend the name Section of Geomagnetism and Upper Atmosphere. E. O.. Hulburt, Chairman N. C. Gerson Ross Gunn David G. Knapp

Cosmic Rays in the Terrestrial Magnetic Dipole Field

The results of scale model experiments with electron orbits in a magnetic dipole field are given in the form of diagrams on big globes. By using these globes it is possible to find the asymptotic directions of cosmic ray particle orbits as a function of momentum and direction of incidence at a cosmic ray recording station. Globes, representing 16 stations are depicted.

New radio telescope for the Department of Terrestrial Magnetism, Carnegie Institution of Washington

New radio telescope for the Department of Terrestrial Magnetism, Carnegie Institution of Washington