bluuebunny/crossref_metadata_2025 huggingface dataset:
Neogene Caribbean Plate rotation and associated Central American tectonic evolution
Authors: Wadge G. , Burke K.
Published: February 2008

During the Neogene the Caribbean plate moved eastward with respect to the North and South American plates. Reconstructing this motion by closing the Cayman Trough along its bounding transform faults creates a gore of ocean between northern Central America and southern Mexico. We present, instead, a reconstruction which juxtaposes these two continental areas by strike slip motion. Using geological evidence from around the Cayman Trough, the strike‐slip fault zones of northern Central America, and the continental margin of southern Mexico as our constraints, we propose that seafloor spreading began in the Cayman Trough at 30 ± 5 Ma and that subsequently there was 1100 km of relative plate displacement at an average rate of 3.7 ± 0.6 cm/yr. This Neogene plate motion cannot be achieved by rigid plate rotation about a single pole, which implies that Central America must have rotated anticlockwise relative to the rest of the plate. There is evidence for internal plate deformation in Central America consistent with such a sense of rotation. Our suggestion of an originally easterly trending arc in southern Central America is more consistent with the timing and geometry of the collision of Panama with northern Colombia and the resultant deformation than were earlier models that depicted collision of a northerly trending arc.
The Lepontine Alps as an evolving metamorphic core complex during a‐type subduction: Evidence from heat flow, mineral cooling ages, and tectonic modeling
Authors: Bradbury Harry J. , Nolen‐Hoeksema Richard C.
Published: February 2008

New surface heat‐flow data are presented for the Valle Maggia region within the high‐grade metamorphic core of the Lepontine Alps. The steady state values range from 44.4 to 55.2 mW/m2 and are anomalously low compared with those measured around the periphery of the Lepontine. These differences are considered to reflect the combined effects of differential uplift and erosion superimposed on a transient, low heat flow regime which has existed since the Miocene. The uplift‐denudation history of the Lepontine is modeled by using various mineral geochronometers. Two major pulses of accelerated uplift are recognized at circa 22 m.y. B.P. and circa 10 m.y. B.P., respectively. These events directly coincide with times of dominant crustal convergence in the Helvetic and Jura stages of A‐subduction. From known PMax–TMax conditions of Oligocene metamorphism, estimates of low mantle heat flow and experimentally determined values of crustal heat production, best fit thermal models are presented to explain surface heat flow and mineral cooling age data for the metamorphic core. A two‐stage underplating model is shown to be consistent with the excavation history of the Lepontine and with geological and geophysical data from more external parts of the Central Alps. This information is integrated to explain the establishment of a crustal‐scale duplex in the Metamorphic Core Complex contemporaneous with thin‐skinned tectonics in the foreland.
Origin, damping, and pattern of development of faults in granite
Authors: Granier Thérèse
Published: February 2008

Observations of brittle fractures in the granite of the Massif de la Borne as well as in other rocks allow us to discuss the different hypotheses regarding the origin of faults. It seems that all faults originate by shear along a preexisting plane which can be an important fracture (joint, former fault) or a microflaw (pore, grain boundary). The shear on the plane gives rise to an array of en echelon cracks that makes the rock less resistant and permits the lengthening of the fault. We also found an arrangement of “horsetail” fractures damping the movements on the faults. We then propose a pattern for the development of the faults. They originate on preexisting plane and propagate by initiating en echelon cracks. The movements are damped by horsetails which permit, by faults connection in relays, the creation of larger faults.
A Kinematic model of southern California
Authors: Weldon Ray , Humphreys Eugene
Published: February 2008

We propose a kinematic model for southern California based on late Quaternary slip rates and orientations of major faults in the region. Internally consistent motions are determined assuming that these faults bound rigid blocks. Relative to North America, most of California west of the San Andreas fault is moving parallel to the San Andreas fault through the Transverse Ranges and not parallel to the motion of the Pacific plate. This is accomplished by counterclockwise rotation of California south of the San Andreas fault and by the westward movement of central California north of the Gar lock fault. The velocities of the blocks are calculated along several paths in southern California that begin in the Mojave Desert and end off the California coast. A path that crosses the western Transverse Ranges accumulates the accepted relative North America‐Pacific plate velocity, whereas paths to the north and south result in a significant missing component of motion. This implies the existence of a zone of active deformation in southern California that is interpreted to include the western Transverse Ranges and northwest trending, predominately strike‐slip faults close to the coast both north and south of the Transverse Ranges. Strain on this system accounts for about a third of the total North America‐Pacific plate motion.
Cocorp deep seismic reflection profiling in the northern Sierra Nevada, California
Authors: Nelson K. D. , Zhu T. F. , Gibbs A. , Harris R. , Oliver J. E. , Kaufman S. , Brown L. , Schweickert R. A.
Published: February 2008

A COCORP seismic reflection profile across the northern Sierra Nevada in California shows several east‐dipping zones of discontinuous reflections. Correlation with surface geology suggests that these zones probably originate from faults of the Foothills fault system. In particular, the Melones fault, which coincides with the “Mother Lode” of the central and southern Sierra foothills, appears to be marked by prominent reflections in the midcrust. Migration of the COCORP data suggests that these faults are approximately planar, have moderately steep east dips (35°–47°), and penetrate at least to midcrustal depths (>20 km). At present it is unclear whether these faults are primary Nevadan thrusts, “late” Nevadan backthrusts (retrocharriage), or younger Cretaceous or Cenozoic faults, also known to occur in the region. Other more problematic features imaged on the profile include a prominent west‐dipping zone of reflections in the midcrust beneath the Eastern belt, and subhorizontal reflections at 22‐ to 26‐km depth beneath the Tahoe graben. The former might represent a west‐dipping thrust analogous to the Taylorsville thrust cropping out to the north of the survey route. The latter might represent the base of the Sierra Nevada batholith, the westward extension of any one of several thrust systems cropping out in Nevada, a low‐angle extensional detachment, or Moho.
The tectonic structure of the Hazara‐Kashmir Syntaxis, southern Himalayas, Pakistan
Authors: Bossart Paul , Dietrich Dorothee , Greco Antonio , Ottiger Robert , Ramsay John G.
Published: February 2008

The stratigraphic and structural features of the Hazara syntaxis are described. A special aim of this work was to integrate modern approaches to rock deformation with the regional tectonics. The region is one of overthrust and shear zone tectonics associated with the development of at least two superimposed sets of major folds and associated minor structures (microfolds, cleavage, vein systems and various types of lineations related to rock strain or intersections of planar structures). It is concluded that the syntaxis results from an early set of nappe units developed by southwestward overthrusting of previously metamorphosed (Himalayan) rocks followed by the formation of a large shear zone structure and finally by the transport of overthrust units from northwest to southeast.
Paleomagnetism of Late Cretaceous and Eocene limestones and chalks from Haiti: Tectonic interpretations
Authors: Van Fossen Mickey C. , Channell James E. T.
Published: February 2008

We have conducted a paleomagnetic study of limestones and chalks from Haiti which suggests that the island of Hispaniola is a composite of at least two tectonically independent blocks. Sampling sites are distributed among three widely separated localities, namely: Les Cayes (nine sites; 18.3°N. Latitude; 73.6°W. Longitude) and Beloc (five sites; 18.4°N. Latitude; 72.6°W. Longitude) which are located on the southern peninsula of Haiti, and a northern locality, Ennery (six sites; 19.5°N. Latitude; 72.5°W. Longitude). Stable magnetization components of dual polarity and moderately high blocking temperature were revealed through progressive thermal demagnetization of samples from all of the Beloc and Ennery sites, while seven of the nine Les Cayes sites possessed unstable magnetizations. Mean paleolatitudes calculated from Beloc and Ennery data show 8° of latitudinal separation that is of at least Eocene age. Pole positions (Beloc: 43.2°N. Latitude; 185.8°E. Longitude, α95=25.1° and Ennery: 66.1°N. Latitude; 31.3°E. Longitude, α95=19.7°) show both colatitudinal and angular discordance with the North American apparent polar wander path. Based on these disparities, we demonstrate that the implied tectonic displacements tend to support some aspects of previously published Caribbean plate tectonic models.
Crustal evolution of the Eastern Canadian Cordillera
Authors: Struik L. C.
Published: February 2008

The Cordillera is not like the Himalayas. The Himalayas are supported by the Indian continent that was thrust under the Asian continent. The eastern Cordillera is supported not by imbricated continents but by imbricated continental margin of the ancient western North America. That ancient margin was compressed and imbricated as it was confined between the North American craton and the minicontinent of Stikinia. In the eastern Canadian Cordillera, tectonic thickening is in the collision zone and not on either side of it, as for example, in the Tibetan Plateau where the underthrust Indian continent has duplicated the thickness of the crust. In the eastern Canadian Cordillera, Jurassic and early Cretaceous thrusts and faults are directed away from the collision zone toward the converging blocks. The oppositely directed thrust faults outline wedge‐shaped sheets of rock. Sedimentary and volcanic rocks (cover), the crystalline rocks on which they were deposited (basement), and the underlying upper mantle may have been detached from each other during the compression. The basement therefore would have imbricated internally between the cover and the mantle as a duplex structure. Confinement of the ancient margin's basement between the colliding blocks requires that the volume of basement under the margin be the same as that presently between the colliding blocks. The possibility of such an equality has been tested and confirmed in cross section. The cross section of the ancient western margin from that test has many features comparable to cross sections recently drawn through the eastern continental margin of Canada.
Evolution of extensional basins and basin and range topography west of Death Valley, California
Authors: Hodges K. V. , McKenna L. W. , Stock J. , Knapp J. , Page L. , Sternlof K. , Silverberg D. , Wüst G. , Walker J. D.
Published: February 2008

Neogene extension in the Death Valley region, SE California, has produced a variety of sedimentary basins. Diachronous movements on an array of strike‐slip and normal fault systems have resulted in the uplift and preservation of older basins in modern ranges. One of the best exposed of these is the Nova basin on the western flank of the Panamint Mountains. The Nova basin includes over 2000 m of sedimentary and volcanic rocks deposited during denudation of the Panamint Mountains metamorphic core complex in late Miocene (?) – early Pliocene time. The principal growth structure for the basin was the Emigrant detachment, which initiated and moved at a low angle. Modern Panamint Valley, west of the range, developed as a consequence of Late Pliocene ‐ Recent, kinematically linked movement on the right‐slip, high‐angle Hunter Mountain fault zone and the low‐angle Panamint Valley detachment. Detailed mapping of the intersection between the Emigrant and Panamint Valley detachments demonstrates that segments of the earlier system remained active during development of Panamint Valley and, thus, during development of modern Basin and Range topography as well. These results indicate that large‐scale extension in the Death Valley region, accommodated by movement on low‐ to moderate‐angle normal fault systems and high‐angle strike‐slip fault systems, is a continuing process. Basin and Range topography in the Panamint Valley ‐ Death Valley area was generated at least in part by displacements on low‐angle detachments rather than high‐angle normal faults.
The age of the Keystone Thrust: Laser‐fusion 40Ar/39Ar dating of Foreland Basin Deposits, southern Spring Mountains, Nevada
Authors: Fleck Robert J. , Carr Michael D.
Published: February 2008

Nonmarine sedimentary and volcaniclastic foreland‐basin deposits in the Spring Mountains of southern Nevada are cut by the Contact and Keystone thrusts. These synorogenic deposits, informally designated the Lavinia Wash sequence by Carr (1980), previously were assigned a Late Jurassic to Early Cretaceous(?) age. New 40Ar/39Ar laserfusion and incremental‐heating studies of a tuff bed in the Lavinia Wash sequence support a best estimate age of 99.0±0.4 Ma, indicating that the Lavinia Wash sequence is actually late Early Cretaceous in age and establishing a maximum age for final emplacement of the Contact and Keystone thrust plates consistent with the remainder of the Mesozoic foreland thrust belt. The reinterpretation of the age of the Lavinia Wash sequence and the consequent limit on the age of foreland thrust faults in the southern Spring Mountains strengthen widely accepted correlations of the Contact‐Red Springs and Keystone thrusts with the Cretaceous Summit‐Willow Tank and Muddy Mountain‐Glendale thrusts in the Muddy Mountains. These correlations were partly in conflict with previously reported ages and geologic interpretations of structures in the Spring Mountains.
Uplift of deep crust during orogenic extensional collapse: A model based on field studies in the Sogn‐Sunnfjord Region of western Norway
Authors: Andersen Torgeir B. , Jamtveit Bjørn
Published: February 2008

The Western Gneiss Region (WGR) in Norway experienced high‐pressure metamorphism during Silurian‐Devonian continent‐continent collision. The eclogite‐bearing lower crust is separated from the middle and upper crust by major detachment zones formed during extensional collapse of the orogen; formation of the Devonian basins is related to the extension. The footwall of the detachment zones comprises three structural and metamorphic zones. The upper zone, zone 1, is characterized by penetrative homogeneous down‐to‐the‐west simple shear developed under retrograde greenschist‐facies metamorphism. Zone 2 suffered inhomogeneous simple shear of the same polarity. Petrography and mineral chemistry data from the lower zone, zone 3, show a record of initial eclogite facies metamorphism at 600°C and >16 kbar, which was decompressed almost isothermally to amphibolite‐facies conditions at 550°C and 10–12 kbar. Both the eclogite‐ and amphibolite‐facies metamorphism developed in a regime of pure shear with vertical shortening. The rapid decompression records an approach of approximately 20 km to the surface, related to uplift that was probably the result of the removal of a thickened thermal boundary layer in the mantle lithosphere. The pure shear regime, which developed initially in the lower crust, was truncated by zones of simple shear as the lower crust was uplifted to middle and upper crustal levels. Extension by simple shear in the upper crust was rooted in the lower crust where extension occurred by pure shear. The shear zones in zones 1 and 2 did not penetrate the pure shear regime of the lower crust. A considerable amount of tectonic stripping of the orogenic welt predates deposition of the Devonian sedimentary basins.
Opposite vergence of Nappes and crustal extension in the French‐Italian western Alps
Authors: Philippot Pascal
Published: February 2008

In the Internal Pennine Zone of the French‐Italian Western Alps (Dora Maira, Monviso, Rocciavre massifs and Queyras region), the structural trends define an apparent “dome” geometry that is truncated to the east by the Pô Basin. This geometry is classically interpreted as a backthrusting system. The kinematic history of the area has been investigated using structural, metamorphic and geochronologic data, on the basis of which two main deformation episodes have been distinguished that occurred under differing metamorphic conditions: (1) The first deformation occurred under greenschist facies metamorphism. It caused a regional scale foliation and an EW trending lineation that lie parallel to ductile deformation zones and thrust contacts. Sense‐of‐shear indicators associated with the lineation indicate contradictory top‐to‐the‐east and top‐to‐the‐west senses of shear. From these, it is deduced that coeval east and west vergent thrust faulting accommodated major displacements between nappes. Phengite Ar‐Ar data yield late Eocene‐early Oligocene ages for the greenschist facies metamorphism. (2) The second deformation caused the widespread development of high‐angle shear bands and normal faults on opposite sides of the Dora Maira massif resulting in the apparent “dome” geometry of the massif. A steep (50–80°) network of west‐dipping normal faults is particularly well developed on the west side of the Dora Maira massif. Differences of 2–3 kbar and 100–150°C between juxtaposed Monviso + Rocciavre and Queyras nappes implies ≥8 km of vertical displacement along the Monviso upper tectonic contact. These normal faults formed in a more brittle regime. Only a post‐early Oligocene age can be estimated from microstructural studies for these final movements. These deformations postdate HP‐LT metamorphism and resulted in the juxtaposition of nappes of distinctly different origin, age, grade, and P‐T‐t history. A kinematic model is presented in which opposite vergence of nappes followed by large‐scale crustal extension occurred in response to uplift during the convergence between the European and South Alpine plates. This model may account for rapid uplift, rapid unroofing and cooling of high pressure‐low temperature rocks (thereby explaining the absence of amphibolite facies metamorphism overprint in this part of the Alps) that may have led to the preservation of coesite‐bearing rocks in the southern part of the Dora Maira massif.
Remarks upon professor Rücker's paper and Wilde's magnetarium
Authors: Bauer L. A.
Published: February 2008

I am constrained to add a few remarks upon the foregoing paper and the interpretation to be put upon the results derived from the “Magnetarium.” Professor Rücker admits that Wilde's results must be received with great caution, and that the conditions under which the experiments were performed are open to legitimate criticism. As I have already had occasion in another connection to point out some of the errors to which “the Magnetarium” results are liable, I shall not enter again upon this matter, but simply accept Wilde's observational results as correct, and endeavor to show what interpretation is to be put upon them.

As Professor Rücker states, “The magnetic field of the earth may be regarded as that primarily due to a uniformly magnetized globe disturbed by some secondary causes.” Furthermore, the result of recent investigations has been that this field originates practically from causes within the earth's crust, and can be referred to a potential. The total magnetic potential on the earth's surface can then be represented by the following terms:

V = Vs + V′s + Vu; Vs = Vp + Ve; V′s = V′p + V′e.
The physical decomposition of the permanent magnetic field of the United States—No. 1. the assumed normal magnetization and the characteristics of the primary resulting residual field
Authors: Bauer L. A. , Hazard D. L.
Published: February 2008

In the March (1899) issue of the JOURNAL, L. A. Bauer published a paper entitled, “The Physical Decomposition of the Earth's Permanent Magnetic Field,” and in that paper were developed the principles and formulae upon which the decomposition was based. The present paper is an application of these principles and formulae for a special portion of the Earth, namely, the United States of America.

This investigation is based upon the series of magnetic charts constructed by Mr. C. A. Schott for the year 1900, and published in Appendix No. 1, Coast and Geodetic Survey Reports for 1896, and 1897. These charts give us the best possible representation of the distribution of the magnetic elements in the United States up to the date of the construction of the charts.
Beobachtungen über die electricitätszerstreuung an der steilen Südküste der Krim
Authors: Rachmanow Von George
Published: February 2008

In diesem Frühling unternahm ich eine Excursion an die Südküste der Krim, um daselbst in verschiedener Seehöhe Beobachtungen über die Electricitätszerstreuung mit einem Apparat nach Elster und Geitel auszuführen. Hier will ich vorläufig einige besonders interessante Daten mittheilen.

Ich bezeichne mit q das Verhältniss,
wo a− die Zerstreuung der negativen und a+ die der positiven Electricität bedeutet. Meine Beobachtungen ergaben folgende Werthe für q.
Report on the magnetic observations made at the magnetic observatory at Pola, Austria, during the time of the total solar eclipse of May 17, 18, 1901
Authors: Kesslitz Wilhelm
Published: February 2008

“Mit Beziehung auf Ihre (T. M., Vol. v, p. 166) Einladung zur Vornahme simultaner erdmagnetischer Beobachtungen am 17. Mai von 14h bis 21h Greenwicher Zeit, wird Ihnen hiemit eine Zusammenstellung der Curven‐Ablesungen vom Magnetographen in Pola u. zw. von Minute zu Minute und die Aufzeichungen des Thermographen Richard für jede 5te Minute des obgenannten Zeit‐Intervalles übersendet.

Die magnetischen Curven nehmen in dieser Zeit einen ganz normalen Verlauf und zeigen keinerlei Störungen.
Report on the magnetic observations made at the University of Groningen during the total solar eclipse of May 17, 18, 1901
Authors: Haga W.
Published: February 2008

At the request of Dr. van Rijckevorsel, I have made in the laboratory of the University of Groningen, during the night between 17–18 May, observations of the variations of declinations and of the horizontal intensity.

The laboratory is quite free from iron, and lies in a garden far from the railway, canals, and frequented streets. In Groningen there are no electric car lines nor electric plants, hence we are undisturbed by stray or “vagabundirende” currents.
Zur Bibliographie von W. Gilbert's “De Magnete”
Authors: Hellmann G.
Published: February 2008

Vor einiger Zeit frug ein Fachgenosse bei mir an, welche Ausgabe von William Gilbert's grundlegendem Werke “De Magnete” die seltenste sei. Ich habe diese Frage nicht ohne weiteres beantworten können, sondern erst einige Nachforschungen darüber anstellen müssen, deren Ergebniss ich wegen der grossen Wichtigkeit und Seltenheit des Buches hier auch weiteren Kreisen mittheilen will.

Zunächst mochte ich betonen, dass es nur drei Ausgaben von Gilbert's Werkgiebt: London 1600, Stettin (Sedini) 1628 und 1633. Die beiden letzten wurden von dem Stettiner Assessor Wolfgang Lochmann besorgt, einem grossen Verehrer der Gilbert'schen Lehren, die damals im Ausland mehr Anklang fanden, als in England selbst.
Ueber die meteorologische Natur der variationen des Erdmagnetismus
Authors: Nippoldt A.
Published: February 2008

Wenn man die Curven unserer Magnetographen betrachtet und von augenscheinlich gestörten Tagen absieht, so zeigt sich uns aufs deutlichste, dass wir es hier mit einem sehr gesetzmässigen Vorgange zu thun haben; dennoch wissen wir über die Quelle dieser Gesetzmässigkeit noch sehr wenig. Die von Schuster geschaffene und von Bezold so eingehend discutierte Theorie der täglichen Variationen, zeigt zwar, dass man ein System magnetischer Kräfte construieren kann, innerhalb dessen die Erde rotiert, und das die genannten Variationen erzeugen konnte, allein damit verlegt sich die Frage nur und lautet jetzt: Wodurch entsteht ein solches System?

Dass es ein rein magnetisches ist, ist unwahrscheinlich, denn die Atmosphäre enthält keine Bestandteile, die genügend magnetisierbar sind, und sie ist doch der Sitz dieser Kräfte. Zwar wäre ein cosmisches Feld denkbar, allein der Verlauf der Kraftlinien trägt doch einen unverkennbar irdischen Character. Daher muss man annehmen, dass das Feld electrischer Natur ist. Dann aber hängen dessen Ströme von der Leitfähigkeit der Luft ab und mithin unter anderem sehr wahrscheinlich von ihrem meteorologischen Zustande. Sie können ausserdem noch in Richtung und Intensität dadurch variieren, dass jene Ursachen variieren, welche die Ströme hervorgerufen haben. Diese Ursachen können ebenfalls terrestrischer Natur, aber auch cosmischen respective solaren Ursprungessein, etwa in der Art der Theorien von Birkeland1 Arrhenius2 und Bigelow,3 die alle darin übereinstimmen, dass sie electrisierte Teilchen von der Sonne ausgehen und zum Teil die Erde treffen lassen. Es sei übrigens hier bemerkt, dass schon vor anderthalb Jahrhunderten Mairan in seinem Traité de l'aurore boréale, p. 455, Paris 1754, zur Erklärung der regelmässigen Variationen angenommen hat, dass von der Sonne feine Teilchen ausströmen, die die magnetische Nadel beeinflussen.
Vorschläge für die Ausführung electrischer Beobachtungen während der bevorstehenden Sonnenfinsterniss
Authors: Elster J. , Geitel H.
Published: February 2008

Die Frage, ob Beobachtungen der electrischen Eigenschaften der Atmosphäre während einer totalen Sonnenfinsterniss mit Sicherheit wertvolle Aufschlüsse über die Natur der atmosphärischen Electricität versprechen, ist, unserer Meinung nach, nur mit Vorbehalt bejahend zu beantworten, nichtsdestoweniger erscheint es geboten, die bevorstehende Finsterniss nicht ungenützt vorübergehen zu lassen.1 Man ist leider noch nicht im Besitze einer vollständigen Theorie, aus der sich voraussagen liesse, welche Erscheinungen in der Zone der Verfinsterung zu erwarten sind und deren Voraussage daher an den Beobachtungen als richtig oder unrichtig erwiesen werden könnte.

Zwar ist bekannt, dass Gase, während sie vom Lichte durchstrahlt werden, eine Ionisierung erfahren können, indem Ionen sowohl im Innern des Gases selbst auf Kosten der absorbierten Lichtenergie gebildet werden, als auch besonders in der Nähe der begrenzenden festen Körper, die während der Bestrahlung negative Electronen aussenden. Aber diese Wirkungen sind für die atmosphärische Luft und für diejenigen festen Stoffe, aus denen die Erdoberfläche besteht, nur für Licht von sehr kleinen Wellenlängen nachgewiesen, die dem Sonnenlichte an der Erdoberfläche fast oder völlig fehlen.
Some problems in radioactivity
Authors: Eve A. S.
Published: February 2008

In the month of May, 1908, by the kindness of the Captain and officers of the S. S. “Lake Erie,” observations were made, between Montreal and Liverpool, on the radioactive deposit collected on a wire, charged negatively by a Zamboni dry pile, and exposed in the air for a few hours. The wire was insulated by ebonite rods, and suspended from the flag halyards. After exposure it was coiled on a skeleton reel and placed in an electroscope. The latter was clamped to a board, together with the observing microscope.
Le projet du levé magnétique de l'Empire Russe et les travaux magnétiques executés en Russie en 1910
Authors: Rykatchew M.
Published: February 2008

Dans mon rapport à la Commission magnétique du Comité Météorologique International, publié dans le Rapport de cette Commission,1 j'ai communiqué le plan du levé magnétique de l'Empire Russe, projeté par la Commission Magnétique, nommée près de l'Académie Impériale des Sciences de St. Pétersbourg. Cette Commission consiste des représentants de l'Académie des Sciences, de l'Observatoire Physique Central Nicolas, des différents ressorts et Institutions, des Sociétés scientifiques, des Universités et des autres établissements et personnes privées, qui ont bien voulu prendre part à l'entreprise.

Le projet du levé magnétique avec le devis a été présenté à l'Académie, laquelle dans sa séance du 13/26 octobre l'a approuvé. Désirant faire tout ce qui est dans son pouvoir pour soutenir cette entreprise elle a décidé d'assigner de son coté pour le levé magnétique 10,000 rb. par an depuis 1912 durant 10 années si elle reçoit le crédit qu'elle demande pour les entreprises scientifiques de l'Académie. Ce don considérable et la bonne volonté des autres institutions et personnes, qui voulent bien prendre part dans nos travaux, nous donne l'espoire que nous parviendrons au but.
The magnetic character of the year 1910
Authors: van Dijk G.
Published: February 2008

The annual review of the “Caractère magnétique de chaque jour,” for 1910 has been drawn up in the same manner as the preceding years. Forty‐three observatories contributed to the quarterly reviews; when the tables were prepared, thirty‐four of them had sent complete data. One of the observatories communicated its method of classification; one adopted another method in the course of the year. Table II of the annual review, containing the mean character of each day and of each month, and the list of “calm days” is reprinted here.
The magnetic survey of Australia
Authors: Bauer L. A.
Published: February 2008

Australia is at present the largest land area in which so comparatively few magnetic observations have been made. With the exception of the portion of Victoria, of which a magnetic survey embracing about 235 points was carried out by the indefatigable Neumayer, between 1858 and 1864, the preliminary magnetic survey of Tasmania by McAulay and Hogg in 1901, and some isolated observations along the coasts, such magnetic results as exist in the interior are confined, well‐nigh exclusively, to compass observations by surveyors.

If it be remembered that the total area involved is over three‐fourths that of entire Europe, and is practically equal to that of the United States (exclusive of Alaska), it will readily be appreciated that there remains here an important field for magnetic exploration. And the importance does not arise merely from purely scientific considerations, but from practical ones as well—navigation, surveying, and exploration of the great interior reaches. The prevalence of local disturbances at some of the ports of call is well known, and mention should be made here of the remarkable local disturbances revealed at Port Walcott on the northwest coast, by the admirable work of H. M. S. Penguin, 1890–93.
Directions for magnetic measurements
Authors: Fisk H. W.
Published: February 2008

Magneticians generally will welcome the appearance of this publication, both because of its excellent presentation of the essentials of field and office practice and because of its general suggestiveness. Its aim is “to present the subject matter in such form that an observer familiar with the use of instruments of precision but without experience in magnetic work may be able to make in satisfactory manner the various observations incident to the determination of the magnetic elements, without other assistance than that to be obtained from these Directions.” Not only has the author effected this purpose but he has also covered the subject of magnetic computations as fully as that of observation, by concise derivation of the various formulae involved, the discussion of their use, and numerous tables particularly helpful to the practical computer. The manual presents in a very concise and finished form, the results of the experience of the United States Coast and Geodetic Survey since its magnetic work was placed on a systematic basis by C. A. Schott, and developed subsequently, in the separate Division of Terrestrial Magnetism of that Survey, under the direction of Dr. L. A. Bauer; the system of observation, and reduction of results, as well as the general directions to observers in the field as given, are essentially those developed by the latter on the foundation laid by Schott.
The physical theory of the Earth's magnetic and electric phenomena: 4. Continued
Authors: Bauer L. A.
Published: February 2008

53. I am grateful to Dr. Steiner for his helpful discussion of the question raised in Nos. III and IV as to whether the Earth is chiefly an electromagnet, due possibly to negative electric currents circulating overhead in the same general direction as that of the Earth's rotation. It may be recalled that this was advanced merely as a working hypothesis in order to ascertain just what conclusions would thereby be implied and how far the hypothesis might assist in explaining the phenomena found in my paper, PD No. II. (Terr. Mag. v. 6, pp. 13–24). The facts of the latter paper will receive fuller treatment in a subsequent number; they appear to be related in some manner to the Earth's rotation.

Steiner agrees with me that the portion of the Earth's magnetism which heretofore was thought almost universally could only be due to internal agencies, can be produced, at least theoretically, equally as well by external electric currents. He is also in agreement with me as to the direction in which these exernal currents would have to circulate around the Earth, viz., from west to east, if negative, and the reverse, if positive. In other words, the direction of the external currents would be precisely the same as that of internal currents supposed capable of causing the Earth's magnetism. If Nos. III and IV accomplish nothing beyond the general recognition of these two facts—that the electric currents may be external ones, and that their direction may be at the same time the same as the supposed internal ones—I shall feel abundantly repaid for the labor bestowed. Given the possibility of an external source, a variety of questions stimulating further research immediately arises.
On the normal magnetic elements at the Mauritius Magnetic Observatory
Authors: Bauer L. A.
Published: February 2008

During a visit on the Carnegie in August, 1911, I had occasion to look into the remarkably disturbed character of the site of the Royal Alfred Observatory at Pamplemousses, Mauritius. Mr. Claxton, while director, had already called attention to the disturbances disclosed by a painstaking and extensive series of declination observations made over an interval of several months at 893 stations, within the area surrounding the old and new sites of the absolute declination observations.1 The declination at these two sites which were located approximately in a true north‐south direction and only 90 feet apart, varied from 9° 15′, at the old site, to 10° 35′, at the new one; from comparisons made twice a day for one year, the adopted difference between the two sites was found to be, 1° 30′. The declinations for standardizing the magnetograph had been made with a Kew magnetometer since 1875 in the old magnetic pavilion where at present the horizontal intensities and dips are still being observed.
Description of the C. I. W. combined magnetometer and Earth inductor
Authors: Fleming J. A. , Widmer J. A.
Published: February 2008

Owing to the difficulties generally experienced in the satisfactory determination of the corrections of dip needles to standard and the possible changes in these corrections with geographical variation in magnetic intensity and inclination and with wear of pivots of the needle, it was found desirable to further improve the universal magnetometer1 of the Department of Terrestrial Magnetism by replacing the dipping needle by an earth inductor attachment. The comparisons made with earth inductors by the observers of the Department in various regions of the globe have been far more satisfactory than the dip circle comparisons.2 In accordance, therefore, with the Director's instructions, the present instrument has been designed and constructed in the shop of the Department. The instrument consists essentially of four parts: (a) the base, (b) the magnetometer attachment, (c) the earth inductor and theodolite attachment, and (d) the galvanometer.
Halley's observations of the magnetic declination, 1698–1700
Authors: Ault J. P. , Wallis W. F.
Published: February 2008

The spelling of the ports visited by Halley's ship, the Paramour Pink, was modernized. It was thought desirable, however, to retain Halley's dates as given by him, which apply to the old style calendar; to refer them to the new style calendar, it would be necessary to add 10 days in 1698–99 and 11 days in 1700.

The latitudes and longitudes, given in the columns headed “Halley's noon position”, are those as published in Halley's journal, all his reckoning being made from noon to noon. The latitude usually results from “a good observation” at noon and the longitude is obtained by reckoning from the previous noon position, except in a very few cases as described in the footnotes.
Bemerkungen zu einem Gewitter in San Carlos de Ancud
Authors: Knoche Walter
Published: February 2008

Am 25.–26. Oktober 1912 rief ein ausserordentlich heftiges Gewitter in San Carlos de Ancud (Hauptstadt der Inselprovinz Chiloé) die grösste Aufregung unter seinen Bewohnern hervor, da Chile in seinen bewohnten Teilen ein ausserordentlich gewitterarmes Land ist. So beobachteten unter 33 meteorologischen Stationen im Jahre 1911, 13 kein, 12 ein, 3 zwei, 2 drei, 2 vier und nur 1 (Santiago) sieben Gewitter und Wetterleuchten (ohne die stillen Entladungen tiber den Anden zu zählen); hierzu kommt, dass die beobachteten Gewitter, z. B. alle sieben in Santiago, meist sehr unbedeutender Natur waren.

Das Gewitter, welches ausser in Nordchiloé auch in der Provinz LLanquihue beobachtet wurde, ist nun dadurch interessant, dass es im Seminario Conciliar yon Ancud mittelst Registrierappkrats. aufgezeichnet wurde. P. Galceran, der Direktor des Seminars, hatte die Freundlichkeit, uns die Registrierstreifen einzuschicken und eine kurze Beschreibung des Apparats zu liefern. Derselbe besteht aus einem Branlyschen Kohärer; der Kohärerstrom (⅓V) schliesst durch ein Relais (mit Klopfer) den Batteriestrom einer Art Morsetelegraph. Die Erdung ist vorzüglich durch Anschluss an den aus Stahlwerk bestehenden Kirchturm erreicht. An diesen ist, gut isoliert, die Antenne yon 80 m Länge bis zur Höhe yon 40 m geführt. Den Ablauf des Registrierstreifens besorgt ein Uhrwerk, mir der sehr grossen Geschwindigkeit von 3.60 m pro 1 Stunde oder 6 cm pro 1 Minute oder 1 mm in der Sekunde. Bei etwa 5 Entladungen in der Sekunde hört die Auflösungsfähigkeit dieses Apparates ftir die Entladungen auf, die. dann einen ununterbrochenen Streifen bilden. Es kamen stellenweise tatsächlich, derartige zusammenhängende Partieen trotz der schnellen Abwicklung vor, die längste 6 sec andauernd, mir einem Minimum also von 30 Entladungen während dieser Zeit.
Magnetic results at Pilar and Luarie Island, Orcadas del Sur, 1905–1912
Authors: Schultz L. G.
Published: February 2008

In the following summaries of magnetic results at Pilar and Laurie Island, Orcadas del Sur, the means are derived from all hours including disturbed days. The Orcadas data are derived from the variometer records: the numerous gaps show that we have been unfortunate with that station up to the past two years, owing to the breaking down of the register clocks and the inexperience of the observers. The absolute observations for the station are much more complete, but it would be most laborious to abstract results from them; however, a fair idea of the secular variation may be obtained from the present data.
The atmospheric‐electric observations on the third cruise of the Carnegie, 1914
Authors: Swann W. F. G.
Published: February 2008

The general course followed by the Carnegie during her third cruise is shown on the accompanying map, Fig. 1. The vessel started from Brooklyn, under the command of Mr. J. P. Ault, on June 8, 1914, arriving at Hammerfest on July 3. Sailing again from Hammerfest on July 25, she arrived at Reykjavik, Iceland, on August 24, having reached the latitude of 79° 52′ North, off the northwest coast of Spitzbergen. Leaving Reykjavik on September 15, the Carnegie arrived at Greenport on October 12, returning to Brooklyn on October 21, 1914.
Correspondence concerning the Commission for Terrestrial Magnetism of the International Meteorological Committee
Authors: van Everdingen E.
Published: February 2008

For the purpose of facilitating correspondence on subjects of a scientific nature during the European war, Prof. Adolf Schmidt, secretary of the Commission for Terrestrial Magnetism, has asked the undersigned to act as intermediary for this correspondence. He accordingly requests that communications or propositions respecting terrestrial magnetism be sent to the undersigned, who will undertake to enter into the necessary correspondence with the Secretary of the Commission or with the members of the Executive Bureau, as the case may be, and communicate the result to the author.
Activity of the Earth's magnetism
Authors: Hazard D. L.
Published: February 2008

At the request of the International Commission for Terrestrial, Magnetism, the “activity” of the Earth's magnetism has been computed for each day of the year 1915 from the records of the Cheltenham Magnetic Observatory, using the method proposed by the late Dr. Bidlingmaier and explained by him in the publication of the results of the Wilhelmshaven observations for 1911.

This method takes the variability of the Earth's magnetism as a measure of its activity, that is, its departure, from moment to moment, from its undisturbed state. As we have not as yet data for determining this undisturbed state, the activity for a day is derived from the departures from the daily mean. This is divided into two parts, namely: the departure of the hourly means from the daily mean and the departure of the individual values in each hour from the mean value for that hour.
On recent secular variation of the magnetic elements in and near Java
Authors: Van Bemmelen W.
Published: February 2008

In the course of the year 1916, my colleague, Dr. J. Boerema, and I had the opportunity of repeating observations at most of the stations in Java visited during the magnetic survey of the years 1903–1907.1 Though we intended also to revisit stations in the outer parts of the Archipelago, various circumstances have thus far prevented us from doing so, and it is not certain that this will be possible in the next few years. Accordingly I think it best to give a preliminary report of the work done, especially since the period considered here (1905–1916) coincides with that of recent surveys covering nearly the whole globe. Only one station at a considerable distance from Java could be visited, viz., Seroetoe, situated between the islands of Billiton and Borneo.
On the magnetic and electric fields which spontaneously arise in a rotating conducting sphere
Authors: Swann W. F. G.
Published: February 2008

There are several ways in which small magnetic and electric fields may be conceived as arising in a rotating conducting body. Thus, centrifugal force will make the free electrons move away from the axis of rotation, until the electrostatic forces brought about as a result of this phenomenon restore equilibrium. The rotation of a body, a sphere for example, may accordingly, from this cause alone, be expected to result in the generation of magnetic and electric fields. Again, in so far as gravity pulls the electrons, they will tend to move towards the center of the sphere and will do so until the electrostatic forces, etc., resulting from this action restore equilibrium.
The magnetic storm of May 13–16, 1921, at Observatorio del Ebro, Tortosa, Spain
Authors: Rodes Father Luis
Published: February 2008

On May 13, 1921, at 13h 10m, there began the most violent magnetic storm registered at this observatory since 1910. The first movement was a very sudden one: towards east in declination, and a decrease in the horizontal intensity, followed by a rapid change to an increase. The oscillation of the vertical component was so rapid that its initial direction could not be determined.

At 19h 18m of May 13 there occurred again sudden jumps in the three elements; there next followed very rapid oscillations, generally of a short amplitude, until the next day, May 14, at 16h 15m, when the general character of the former perturbation was reproduced with a maximum intensity between 22h 15m, May 14, and 8h, May 15, during which time the curves left the photographic sheet several times; the H‐component particularly remained off the sheet from 3h to 11h, May 15, and 8h to 10h, May 16.
The magnetic storm of May 13–17, 1921, at Watheroo Observatory, Australia
Authors: Parkinson Wilfred C.
Published: February 2008

A magnetic disturbance of exceptional severity has been recorded by Watheroo magnetographs during May 13–17, 1921. The time used throughout is 120th east meridian standard time, designating midnight as 0h and noon, 12h. The disturbance began at 21h 09m on May 13, the commencement in all three elements being very sudden. The H (horizontal intensity) increased by about 70γ and the Z (vertical intensity) decreased by about 27γ almost immediately.
The magnetic character of the year 1920
Authors: van Dijk G.
Published: February 2008

The annual review of the “Caractère magnétique de chaque jour” for 1920 has been drawn up in the same manner as for the preceding years. Thirty‐nine observatories contributed to the quarterly reviews, 36 of them having sent complete data.

Table II of the annual review, containing the mean character of each day and each month, the list of calm days and the days recommended for reproduction, are reprinted here.
Report on magnetic observations made by the National Observatory of Mexico during the total solar eclipse of September 10, 1923
Authors: Gallo Joaquin
Published: February 2008

In accordance with the plan outlined1 by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, special magnetic declination observations were made at Yerbanis, Durango, in the path of totality, on September 10, 1923, by Sr. Ingeniero Rosendo O. Sandoval, in charge of the Magnetic Department of the National Observatory.

Using Dover magnetometer, No. 126, eye‐readings were made every minute from 17h 28m to 24h 02m, G. M. T. The results are given in Table 1. The geographic position of Yerbanis is as follows: latitude, 24° 44′ North; longitude, 104° 10′ West of Greenwich.
The computation of tabular quantities
Authors: Neumann Frank
Published: February 2008

There is one phase of magnetic work which, although only of secondary importance as compared with its theoretical problems, is nevertheless of real practical importance to those who have in hand the preparation and publication of the results of magnetic observatory observations. It may be of interest to describe some of the methods which have recently been found effective in facilitating the preparation of the magnetic observatory results for the five observatories of the Coast and Geodetic Survey. Reference will be made only to the computation of the hourly values of the magnetic elements and to the diurnal variation tables.

The hourly values of declination, horizontal and vertical intensities are, of course, computed by simply adding the converted hourly magnetogram scalings to constant base‐line values and applying corrections for temperature when necessary. There are several ways in which this may be done, depending largely on the facilities at hand and on the preferences of individual computers. The system to be described here includes the use of an addition table and a special copyholder, and these, when used in conjunction with a touch system adding and tabulating machine, enable computers with even very limited experience to attain a high degree of speed and accuracy. When it is realized that as many as three or four thousand tabular quantities might be computed in the course of a day, the reason for great attention to detail becomes very evident.