bluuebunny/crossref_metadata_2025 huggingface dataset:
The Tripoli, Libya, Earthquake of September 4, 1974: Implications for the active tectonics of the central Mediterranean
Authors: Westaway Rob
Published: February 2008

Source parameters have been determined for the earthquake (Ms 5.6) that occurred offshore of Tripoli, Libya, on September 4, 1974. One nodal plane of its focal mechanism has dip 37°, strike 297°, and rake −141°, indicating oblique normal faulting. This nodal plane is subparallel to many west‐northwest striking normal faults in the epicentral area and is most likely the fault plane, indicating a component of right‐lateral strike‐slip with slip vector azimuth N84°E. Inversion of long‐period teleseismic body waves indicates 12‐km centroid depth and 0.4 × 1018 N m seismic moment. A much larger earthquake (Ms 7.0) on April 19, 1935, that occurred in the same zone of active oblique normal faults ∼400 km farther southeast near Sirte probably involved similar slip sense. This zone, for which the name “Tunisia‐Libya seismic zone” appears appropriate, has overall northwest‐southeast extent ∼1000 km from northern Libya to between Tunisia and Sicily. It takes up a change in motion direction relative to stable Europe from west of north inside the African plate to between N30°E and N50°E in the Ionian Sea between Sicily, southernmost peninsular Italy, southwest Greece, and Libya. This suggested motion direction of Sicily relative to stable Europe agrees with independent estimates from fault slip rates and senses elsewhere in Italy.
Determining deviatoric stress tensors from calcite twins: Applications to monophased synthetic and natural polycrystals
Authors: Laurent Philippe , Tourneret Christophe , Laborde Olivier
Published: February 2008

Theoretically, calcite twins analysis makes possible the full determination of the deviatoric stress tensor responsible for the formation of the twin lamellae, that is, the orientations of the principal stress axes and the three differential stress values (σi–σj) may be calculated, assuming conditions of constant resolved shear stress for twinning. Inverse method using nonlinear regression and robust estimation is proposed.

Applications to monophased synthetic polycrystals that are generated numerically by solving the direct problem and to a natural sample from the Quercy (southwest of France) have given good results. Comparison with the first method proposed by Turner (1953), modified by Nissen (1964) for principal stress orientations and by Jamison and Spang (1976) for differential stress values, clearly emphasizes the considerable interest of this new method.
Structural development of the Western Metamorphic Belt adjacent to the Coast Plutonic Complex, southeastern Alaska: Evidence from Holkham Bay
Authors: Stowell Harold H. , Hooper Robert J.
Published: February 2008

The Coast plutonic complex in southeastern Alaska and British Columbia is bordered on the west by low‐ to medium‐grade metamorphic rocks of the western metamorphic belt. This belt includes intensely deformed rocks underlying a prominent topographic low, the Coast Range megalineament. Structural data from the northern part of the belt near Holkham Bay, southeastern Alaska, constrain the shear sense during polyphase deformation. Tectonite fabrics within the western metamorphic belt record at least three deformational events. Variation in foliation development, fold geometry, and metamorphism indicate that deformation was heterogeneously partitioned. Four tectonic zones can be defined; the peninsular, Coast Range megalineament, coherent, and straight zones. The earliest recognized deformation resulted in folding that transposed bedding into a tectonite layering (S1) throughout the western metamorphic belt. These structures are inferred to have developed during late Cretaceous crustal thickening that resulted in moderate‐ to high‐pressure metamorphism. Later deformation (probably early Tertiary) resulted in abundant mesoscopic and macroscopic F2 folds of S1 and development of shear bands in the Coast Range megalineament zone. The vergence and variation in plunge of F2 folds are compatible with subvertical east‐side‐up displacement across the Coast Range megalineament zone (uplift of the Coast plutonic complex). Shear bands indicate right‐lateral strike‐slip motion occurred during the waning stages of metamorphism, probably following development of F2 folds. Brittle faults parallel to the Coast Range megalineament contain subhorizontal slickensides suggesting additional strike‐slip movement.
Kinematic constraints on distributed lithospheric deformation in the equatorial Indian Ocean from present motion between the Australian and Indian Plates
Authors: Gordon Richard G. , DeMets Charles , Argus Donald F.
Published: February 2008

From an expanded, accurate, and up‐to‐date data set comprising 110 spreading rates, 46 transform azimuths, and 151 earthquake slip vectors from the Indian Ocean and Gulf of Aden, we determine a new rigid plate model describing the motion since 3 Ma between India and Australia. The Euler vector (ω = 0.313°/m.y. about 5°S, 78°E) lies near the middle of the equatorial, diffuse plate boundary dividing the Indian from the Australian plate and predicts a rate of north‐south shortening along 85°E of 4±3 mm/yr, only 30% as fast as predicted by our prior model. The new model also predicts north‐south extension of 6±2 mm/yr (at 68°E) along the western segment of the diffuse plate boundary, where our prior model predicted north‐south contraction. Using data only along the Carlsberg and Central Indian ridges and no other plate boundaries, we show that plate motion data cannot be fit by a single Euler vector. However, the data are well fit by two Euler vectors when an east‐west striking India‐Australia plate boundary is assumed to intersect the Central Indian Ridge near the equator. The best location along the Central Indian Ridge for this triple junction is 6°S–3°S, with 95% confidence limits of 9°S–4°N, just west of a region of intense seismicity. The sense of deformation, as recorded in earthquake focal mechanisms, reverse faults mapped with reflection seismic data, and undulations in basement topography, surface gravity, and the geoid, agrees well with the north‐south extension predicted in the western part and the north‐south shortening predicted in the eastern part of the India‐Australia boundary. The predicted rate of north‐south shortening between 79°E and 86°E is consistent with the rate of shortening inferred from observed faulting and folding; shortening taken up by faulting is ∼6 to 100 times greater than that taken up by the spectacular basement folds. Little of the rapid north‐south shortening predicted east of ∼86°E is taken up by crustal thickening. Instead, lithosphere is transported northeastward toward the Sumatra trench through strike‐slip faulting and possible clockwise rotation. The failure of the convergent segment of the diffuse plate boundary to form a subducting trench provides some new observations that must be satisfied by models for the initiation of subduction. A model of separate, rigid Indian and Australian plates divided by a diffuse plate boundary appears to be valid and useful because the predictions of the model agree with independent data and because the predicted velocity of relative motion is statistically significant and comparable with that across other plate boundaries.
Breakup of young oceanic lithosphere in the upper part of a subduction zone: Implications for the emplacement of ophiolites
Authors: van den Beukel Jilles
Published: February 2008

It is investigated, by means of numerical modelling, whether the interaction between young oceanic lithosphere and a subduction zone can lead to the breakup of a young and thin oceanic plate. First, a thermal model of the upper part of a subduction zone (the region between the trench and the volcanic arc) is presented. Temperatures are modelled for situations in which the age of the subducting oceanic lithosphere gradually decreases, culminating in the arrival of a spreading ridge at the trench. Temperatures are used to infer the strength of material within the subducting plate from a pressure and temperature dependent rheology. Next, it is investigated by means of finite element modelling whether the forces acting upon young subducting oceanic lithosphere, recently created at a spreading center in the vicinity of a subduction zone, can lead to its breakup. Our modelling results show that very young oceanic lithosphere may indeed break up during the early phase of its subduction. Whether breakup occurs depends upon the spreading velocity and the length of the ridge segment that interacts with the trench. If breakup occurs, some young oceanic lithosphere situated in the upper part of the subduction zone and in the region between the ridge and the trench will be detached from the other parts of the subducting plate. The detached sheet of thin oceanic lithosphere will not be subducted to mantle depths. Instead, subduction of the trailing plate, at the opposite side of the ridge, can lead to the incorporation of this sheet into the forearc region. Our modelling provides a mechanism to incorporate thin oceanic lithosphere into an arc‐trench region and eventually, upon closure of the ocean basin, into an orogenic belt. It is shown that a large subset of ophiolites (those with a harzburgite‐dominated mantle section) has properties in good agreement with an emplacement history in which the breakup of young oceanic lithosphere in the upper part of a subduction zone is the first phase.
Crustal extension in the northern Apennines: The transition from compression to extension in the Alpi Apuane Core Complex
Authors: Carmignani L. , Kligfield Roy
Published: February 2008

An interpretation of Northern Apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge, after a model proposed by Platt [1986], followed by the initiation and development of continental rifting. During Cretaceous to Eocene time an accretionary wedge formed as remnant Tethyan oceanic crust subducted beneath the rotating Corsica‐Sardinia microplate. Microplate collision during the Oligocene was characterized by the rapid imbrication of buoyant continental crust of the Italian continental margin, the record of which is preserved within the duplex structure geometry of the Alpi Apuane region. The overthickened wedge geometry returned to a more stable configuration by developing extensional features during the Miocene: both listric normal faults at upper‐crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid‐crustal levels are recorded. It is proposed that large‐scale regional extension with associated volcanism beginning in the Messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex. Further rifting, perhaps aided by subduction and back arc processes in the Southern Apennines, led to the formation of the Tyrrhenian Sea as an oceanic basin. Both the Apennines and North American core complexes record evidence of crustal thickening followed by crustal thinning, and finally of continental rifting. This suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges.
Grustal shortening in the Alpine Orogen: Results from deep seismic reflection profiling in the eastern Swiss Alps, Line NFP 20‐east
Authors: Pfiffner O. A. , Frei W. , Valasek P. , Stäuble M. , Levato L. , DuBois L. , Schmid S. M. , Smithson S. B.
Published: February 2008

The deep crustal seismic line NFP 20‐EAST crosses almost the entire Swiss Alps. Despite the complex geometry of the well‐exposed nappe structure and the considerable axial plunge of some of the units, the Vibroseis survey yielded coherent reflections from several individually identifiable nappe contacts. In the northern part of the survey the Vibroseis data closely match the internal structure of the Helvetic nappes and the underlying autochthonous‐parautochthonous Mesozoic sediments. On the northern flank of the Aar massif, an external basement uplift, these Mesozoic sediments seem to rise from a depth of approximately 7–8 km below sea level to the surface in a series of steps which is interpreted to represent crustal shortening achieved by a combination of folding and thrusting. In the southern part of the survey it was possible to image a number of thin slivers of Mesozoic carbonates pinched between slabs of Penninic basement nappes as well as nappe contacts between lithologically contrasting units. In addition, it seems that the Insubric fault zone, which marks the contact between the Penninic zone and the Southern Alps and which outcrops about 30 km to the south of the survey, shows up as steeply north dipping reflections. The lower European crust in the northern part of the survey is relatively transparent as opposed to the Adriatic lower crust, whose reflective nature may stem from shear zones associated with Mesozoic crustal stretching. The base of both the European and Adriatic crust coincides with a 1‐s‐thick band of laterally discontinuous reflections. This reflection Moho drops to greater depths going from the north toward the center of the Alpine chain, where it disappears with a steep southerly dip. The Moho reappears as a reflection band farther south. This Moho gap is situated above the lithospheric root and may be caused by perturbations related to subduction of lower crustal material. The crustal‐scale structure obtained from the Vibroseis data may be interpreted as a continent‐continent collision with wedge‐shaped indentation of a piece of Adriatic crust into the European crust and vertical escape of the material in the core of the orogen along steeply dipping faults.
Evidence of Uppermost Proterozoic to Lower Cambrian miogeoclinal rocks and the Mojave‐Snow Lake Fault: Snow Lake Pendant, central Sierra Nevada, California
Authors: Lahren Mary M. , Schweickert Richard A. , Mattinson James M. , Walker J. Douglas
Published: February 2008

Displaced uppermost Precambrian to Lower Cambrian miogeoclinal strata occur within Snow Lake pendant in the central Sierra Nevada. These rocks have been correlated with the Stirling Quartzite, the Wood Canyon Formation, the Zabriskie Quartzite, and the Carrara Formation in the western Mojave Desert and the San Bernardino Mountains (Lahren and Schweickert, 1989; Lahren, 1989). This correlation is based on new, updated, and previously reported data including (1) lithologic similarities, (2) overall stratigraphic sequence, (3) vertical sequence within individual formations, (4) approximate stratigraphic thicknesses, (5) Skolithos in the correct stratigraphie position, (6) depositional environments, and (7) petrographic character and provenance of quartz arenites. The correlation is strengthened by the fact that Snow Lake pendant and the western Mojave share many other close similarities including (1) initial 87Sr/86Sr ratios of associated granitic rocks >0.706, (2) passive margin tectonic setting of Precambrian to Cambrian miogeoclinal rocks, (3) dikes of the Independence dike swarm, (4) possible Lower Triassic overlap sequence, the Fairview Valley Formation, (5) petrographically similar gabbroic complexes of the same age, (6) associated eugeoclinal rocks, and (7) identical(?) pre‐Tertiary structural configuration. New U/Pb zircon geochronology unequivocally shows that dikes at Snow Lake pendant are coeval with the Independence dike swarm of the eastern Sierra and the western Mojave desert and that associated gabbroic complexes in both the Mojave and Snow Lake pendant are the same age. Correlation of Snow Lake pendant with the western Mojave requires about 400 km of dextral displacement of the rocks of Snow Lake pendant, together with associated rocks (Snow Lake block), from the western Mojave Desert along the Mojave‐Snow Lake fault. Displacement most likely occurred after 150 Ma, the age of the Independence dike swarm, and before about 110 Ma, the age of major plutons within the Sierra Nevada batholith. This interpretation, if correct, holds major implications for allochthonous terranes west of Snow Lake pendant, which were probably attached to the Snow Lake block before its northward transport. In addition, a number of Paleozoic and Mesozoic tectonic features in western Nevada and eastern California may have been offset dextrally along the proposed Mojave‐Snow Lake fault.
Über die Möglichkeit, vollständige magnetische Observatorien ganz Oberirdisch und in einem gebäude Einzurichten
Authors: Wild Von H.
Published: February 2008

Herr Professor M. Eschenhagen hat in Nr. i des IV. Bandes dieser Zeitschrift meinen Plan für Einrichtung magnetischer Observatorien1 in einer Weise besprochen, welche meines Erachtens über den Zweck und die Bedeutung meines Vorschlags zu irrigen Meinungen führen könnte. Es sei mir daher gestattet, hier im Interesse der Sache einige rectificirende Bemerkungen zu dieser kritischen Besprechung zu machen und die in Betracht kommenden Fragen etwas eingehender zu erörtern.

Herr Eschenhagen möchte meinen Plan, der die Vereinigung der absoluten erdmagnetischen Messungen und der Variations‐Beobachtungen in einem oberirdischen Gebäude vorschlägt, nur für solche Fälle adoptiren, wo es aus ökonomischen Rücksichten nicht möglich sei, mehrere Gebäude zu errichten. Da es ihm wichtig erscheint, sowohl für die absoluten Messungen als für die Variations‐Beobachtungen je zwei Serien verschiedener Instrumente in einem vollständigen magnetischen Observatorium zu haben, so hält er es für besser, wie bisher zwei getrennte Gebäude zu erstellen, das eine, oberirdische, für die beiden Serien der Instrumente zu den absoluten Messungen, und das andere, unterirdische, für die zwei Serien von Variationsinstrumenten, wie dies kürzlich in Potsdam eingerichtet worden sei, nachdem sich dort die seit 1890 bestehende Vereinigung der absoluten Messungen und der Variations‐Beobachtungen in einem Gebäude, nämlich die letztern im Keller und die erstern im Erdgeschoss darüber, nicht bewährt habe. Ausserdem solle noch ein drittes Gebäude für besondere Untersuchungen in grösserer Entfernung von den erstern daselbst erstellt werden.
Completes oberirdisches Observatorium
Authors: Wild Von H.
Published: February 2008

In einem Artikel “Ueber die Einrichtung magnetischer Observatorien”1 habe ich den Plan eines magnetischen Observatoriums mitgetheilt, bei dem in einem einzigen oberirdischen Gebäude nicht bloss die drei Instrumente für absolute Messungen der Declination, Inclination und Horizontal‐Intensität mit ihren Magneten, sondern auch zwei Serien von Variations‐Instrumenten für Declination, Horizontal‐ und Vertikal‐Intensität (die eine Serie selbstregistrirend) so untergebracht waren, dass dieselben innerhalb der Genauigkeitsgrenzen bei derartigen Beobachtungen keinen störenden Einfluss aufeinander ausüben. Die Gründe, welche mich zu dieser, von der üblichen abweichenden Einrichtung bewogen, habe ich schon dort, viel ausführlicher aber in meinem, in dieser Nummer veröffentlichten Artikel: “Ueber die Möglichkeit, vollständige magnetische Observatorien ganz oberirdisch und in einem Gebäude einzurichten” dargelegt. Wenn man aber darnach in oberirdischen Gebäuden dieselben Bedingungen constanter resp. sehr langsam variirender Temperatur realisiren und überdies die störende Feuchtigkeit viel leichter vermeiden kann als in unterirdischen Räumen, warum sollte man dann nicht lieber die erstern auch für die magnetischen Variations‐Instrumente wählen, und wenn man die letztern zusammen mit den Instrumenten für die absoluten Messungen ohne Befürchtung gegenseitiger Störungen bei passender Anordnung in ein und demselben Gebäude unterbringen kann, warum sollte man diese Bequemlichkeit aufgeben und sie durchaus auf zwei Gebäude vertheilen wollen? Diesen Erwägungen zufolge dürfte es daher den Lesern dieses Journals nicht unlieb sein, die am letzern Ort bereits erwähnte zweite, in mehrern Beziehungen vortheilhaftere Lösung des fraglichen Problems kennen zu lernen.
Sur la rélation qui existe entre la répartition des éléments magnétiques et la distribution générale des mers et de la température moyenne annuelle à la surface du globe
Authors: de Tillo Alexis
Published: February 2008

Dans l'Atlas des isonormales du magnétisme terrestre, publié en 1895,2 j'avais émis la conviction que par rapport à chaque élément magnétique le globe représente deux hémisphères dans le sens longitudinal. Aujourd'hui j'ai l'intention de prouver cette thèse en prenant les différences entre les valeurs des éléments magnétiques des méridiens opposés. Je me limiterai aux latitudes comprises entre les degrés 60 Sud et 60 Nord, en excluant les contrées polaires; premièrement à cause de l'incertitude de leur connaissance, et secondement parce que les régions polaires avec le phénomène des auroras boréales doivent être envisagées autrement.

Les Tables fondamentales du magnétisme terrestre, publiées en 1896 par la Société Impériale Russe de Géographie contiennent déjà les valeurs moyennes des éléments magnétiques pour les méridiens à distance de 10° pour les époques 1829, 1842, 1880 et 1885, d'après les autorités principales (Erman et Petersen, Sabine, Creax et Neumayer).
The United States Coast and Geodetic Survey: its origin, development, and present status
Authors: Preston E. D.
Published: February 2008

The United States Coast and Geodetic Survey owes its origin present status to certain Acts passed by the United States Congress in the years 1807, 1832, and 1843. The ultimate necessity of a great national work was foreseen by Washington, who had himself been a surveyor. Jefferson, the third President of the United States, having passed five years in diplomatic service abroad, realized the importance of the project from a commercial standpoint, and during his administration the first formal action was taken by Congress. Twenty‐five years later, after the country had again passed through the bitter experiences of war, the strategic aspect of the work was appreciated, and during the presidency of Jackson a new impetus was given to the undertaking.
A possible cause of the earth's magnetism and a theory of its variations
Authors: Sutherland William
Published: February 2008

A possible cause of the Earth's magnetism is the rotation of an electrostatic field within the Earth, as Rowland's experiments have proved (Phil. Mag. [5] xxvii) that a moving charge of electricity produces a magnetic field analogous to that of a current. If the Earth carries round an electrostatic field in its rotation, then it will have the axis of its magnetic field identical with the axis of rotation which is the chief approximate fact of the Earth's magnetism. The actual obliquity of the magnetic to the rotational axis is traced to unsymmetrical magnetic permeability of the Earth, which also causes the induction of Earth currents, the secular variation of whose tracks is the cause of magnetic secular variation.

The theory advanced to account for daily variation is that under the action of the Sun's rays the oxygen and ozone of the atmosphere become the active substance of a large secondary battery or accumulator whose alternate charge and discharge are the cause of the daily variations.
The magnetic “postturbation” and the current vortices of Schmidt
Authors: van Bemmelen W.
Published: February 2008

The recent article, by Dr. Adolf Schmidt, in the Meteorologische Zeitschrift, 1889, p. 385» entitled, “Uber die Ursache der Magnetishen Stürme,” induces me to return to my paper, published in the same journal (1895, p. 321), “Die Erdmagnetische Nachstörung,”. The phenomena of disturbance described in my paper, examined anew by the light of Dr. Schmidt's considerations on moving current‐vortices, furnish, in my opinion, new indications for an explanation of the nature of magnetic disturbances. For this purpose I propose to recapitulate briefly the chief results of the investigations concerning the phenomenon described by me, which I term the magnetic “postturbation,” or the magnetic after‐disturbance effect.

The daily means of the magnetic elements observed at the different observatories formed the principal basis for these inquiries. A superficial look at those quantities—e. g., for Pawlowsk—shows that immediately after a magnetic storm the horizontal force is generally less than it was before, and that it increases during the following days. A synoptical tabulation of a number of such series of diurnal means confirmed this result; it showed, in the majority of cases, that the horizontal force increases regularly after any magnetic storm, and that the westerly declination decreases. The vertical component mostly decreased, though not with the same regularity.
Magnetic observations made at the magnetic observatory, Zi‐Ka‐Wei, China, during partial solar eclipse, November 11, 1901
Authors: de Moidrey J.
Published: February 2008

L'éclipsé de soleil du 11 novembre dernier a été visible ici comme éclipse partielle (grande phase 0.616 vers le coucher du soleil). Les observations astronomiques et météorologiques ont présenté peu d'intérêt. Quant à l'étude des effets magnétiques de l'éclipsé, la conclusion de notre travail parait bien être négative. Je vous envoie néanmoins nos chiffres dans la pensée que, si on a fait des observations ailleurs, la comparaison pourra être instructive.
Results of international magnetic observations made during the total solar eclipse of May 18, 1901, including results obtained during previous total solar eclipses
Authors: Bauer L. A.
Published: February 2008

During the total solar eclipse of May 28, 1900, a slight magnetic effect that appeared to be directly associated with the passage of the shadow cone from place to place was observed at various stations, distributed within or close to the belt of totality, in the southeastern part of the United States.1

The analysis of the effect showed that it was not a phenomenon similar to a cosmical magnetic disturbance, the beginning of which takes place practically simultaneously over a very large area and, in many instances, over the entire earth, but that the occurrence of the various phases of the effect was closely related to the times of totality at the various stations. Furthermore, the indications were that the source of the effect was to be attributed to some change which occurred outside of the Earth's crust. It was also shown that this effect differed from an ordinary cosmical magnetic storm in that it began, progressed, and ended gradually; in brief, that it consisted of a wave of the periodic variation kind so that it was not proper to term it a “disturbance” or “perturbation,” but a magnetic oscillation or variation.
The physical decomposition of the Earth's permanent magnetic field, No. III
Authors: Bauer L. A.
Published: February 2008

a. The Earth's Total Magnetic Energy.

b. The Seat of the Principal Cause of the Secular Variation.

c. On the Improvement of the Gaussian Theory.
Beschreibung des neuen magnetischen Theodoliten, “Bamberg” NR. 7904, am magnetischen Observatorium in Pola
Authors: Kesslitz W.
Published: February 2008

Die nachstehenden Figuren 2 und 4 stellen die beiden von einander unabhängigen Theile des Theodoliten, nämlich das Instrument zur Winkelmessung und den Apparat für die Bestimmung der Schwingungsdauer in perspectivischer Ansicht dar

Das Instrument wurde von der Firma Carl Bamberg in Friedenau bei Berlin gebaut, wobei der Normal‐Theodolit in Potsdam als Modell gedient hat und verschiedene Verbesserungen nach den Angaben des damaligen Leiters vom magnetischen Observatorium, Professor Dr. M. Eschenhagen, angebracht worden sind.
Über die radioactivität der erdsubstanz als eine der ursachen des Ionengehaltes der atmosphäre
Authors: Elster J. , Geitel H.
Published: February 2008

Durch den Nachweis eines normalen Gehalts von electrischen Ionen in der atmosphärischen Luft,1 mit anderen Wortes, eines gewissen Leitvermögens, ist die weitere Frage nach der Quelle dieser Ionisierung nahegelegt. Die Untersuchung begegnet einer, wie es scheint, sehr ernsten Schwierigkeit, die darin liegt, dass es unmöglich ist, Luft oder irgend ein Gas ohne Vermittelung fremder, starrer oder flüssiger Körper abzugrenzen, deren Einfluss auf den Ionengehalt des Gases, wie im folgenden noch deutlicher hervortreten wird, von vornherein nicht zu erkennen ist.

So kommt es, dass selbst in dem einfachsten Falle, nämlich für begrenzte Luftmassen, unter bekannten physicalischen Bedingungen noch nicht mit Sicherheit entschieden werden kann, ob die Ursache der Ionenbildung in der Luft selbst oder wesentlich in einem Einflusse der begrenzenden Wände zu suchen ist. Hiernach könnte es fast hoffnungslos erscheinen, den Ionengehalt der freien Atmosphäre, in der so viele Prozesse chemischer und physicalischer Art durcheinanderlaufen, auf bestimmte Quellen zurückführen zu wollen. Und doch wird dies Vorhaben ausführbar, sobald man auf Vollständigkeit verzichtet und nur solche Ursachen der Ionisierung berücksichtigt, die in deutlich messbarer Intensität tätig sind. Im Folgenden soll eine solche, nämlich die Radioactivität des Erdbodens, eingehender behandelt werden.
The physical decomposition of the earth's permanent magnetic field: No. IV
Authors: Bauer L. A.
Published: February 2008

a. Introductory Note.

b. Secular Motion of a Free Magnetic Needle.

c. Vertical Earth‐Air Electric Currents.

d. Residual Magnetic Field and Diurnal Variation Field.
Magnetic survey of the Dutch East Indies
Authors: van Bemmelen W.
Published: February 2008

The annual amount of the secular variation in the remote parts of the Archipelago is not positively known; the low values of easterly declination found in March, 1904, in the northern part of Sumatra, make it obvious that hypothetical values are not to be relied upon.

The best way to eliminate, as far as possible, this uncertainty is to obtain values of the magnetic elements in the remoter parts of the Archipelago in one and the same year. For this reason also the northeastern and southern boundaries of the region to be surveyed were likewise visited during 1904. Besides two trips, respectively, to Engano in June, and to Christmas Island in July, a great number of stations in Celebes, the Molluccos and northern New Guinea have been visited during the months August, September, and October of that year.
Earth‐currents and a proposed method for their investigation
Authors: Burbank J. E.
Published: February 2008

Sir Humphrey Davy26 appears to have been the first to suggest the possibility of currents of electricity flowing in the earth, and states that the variation in the declination may be caused by the variations of these currents. Christie carried the suggestion still further in his “Theory of the Diurnal Variation of the Earth's Magnetism”23 and argued that the heat of the sun was the cause of these currents; he constructed a model to test this point. Becquerel16 made some experiments in 1844 to find whether the Earth's magnetism had an electrical origin, but his results seem to indicate effects due to the electrochemical action of the plates and the soil. W. H. Barlow10 from his observations on the English telegraph lines in 1847 appears to have been the first to prove that the currents which often interfered with the sending of messages actually came from the Earth and were always present.
Die absolute Messung der specifischen Leitfähigkeit und der Dichte des verticalen Leitungsstromes in der Atmosphäre
Authors: Gerdien H.
Published: February 2008

Leitungsstrom und Convectionsstrom.

Die electrischen Strömungen in der Atmosphäre setzen sich aus zwei Anteilen zusammen: dem Leitungsstrom und dem Convectionsstrom;1 unter Leitungsstrom soll im folgenden der dem electrischen Felde und der specifischen Leitfähigkeit proportionale Strom verstanden werden, unter Convectionsstrom der von dem electrischen Felde unabhängige, durch die Bewegung freier electrischer Ladungen vermittelte Strom. Dann ergiebt sich für die Componenten der Gesammtstromdichte:
jy = ... ... ... ... ... .jz = ... ... ... ... .....worin V das electrische Potential, ϵ die Ladung des einzelnen Ions, np1, np2 ... nph, nn1 ... die specifischen Zahlen der positiven und negativen Ionen der Gattung 1, 2, ... h, vp1, vp2 ... vph, vn1 die specifischen Geschwindigkeiten der positiven und negativen Ionen der Gattung 1, 2, . . h, ρ1, ρ2 ... ρk die räumlichen Dichten der freien Ladungen von der Gattung 1, 2, ... k, G1, G2, ... Gk die Geschwindigkeiten dieser Ladungen bedeutet.
Magnetische Messungen in Sibirien
Authors: Smirnow Von D.
Published: February 2008

Diese Messungen sind auf Initiative des Herrn Professors der Kaiserlichen Universität in Tomsk, Th. Kapustin, mit dem Wild'schen Reise‐Universaltheodolith aus der Werkstatt von Edelmann in München gemacht worden.

Als eins der ersten Exemplare seiner Art, weicht dieses Instrument unwesentlich von der Beschreibung ab.
Some atmospheric radioactivity observations made at Washington, D.C., showing presence of thorium in the air
Authors: Burbank J. E.
Published: February 2008

Since the discovery by Elster and Geitel of the induced radioactivity obtained on a negatively charged wire when exposed in the free air, several investigators have carried out similar observations. The researches of Elster and Geitel showed an induced radioactivity, which decayed at approximately the same rate as that obtained from radium.

Rutherford and Allen, at Montreal, carefully investigated the rate of decay for a wire exposed in the open air, and found that the radioactivity thus resulting decreased to one‐half value in about forty‐five minutes, whereas the radium‐induced activity does not decrease very regularly until after about two hours, and then decays exponentially, falling to half‐value in twenty‐eight minutes. Allen has since confirmed his previous observations.
On the nature of the effect of the sun‐spot frequency on the variation of the magnetic elements at the Cape of Good Hope
Authors: Fincham G. H. H.
Published: February 2008

The influence of the Sun‐spot frequency on the magnetic elements has been discussed by many investigators during recent years. The observations upon which the present investigation is based are those taken by the royal artillery during the years 1842–46 and published by Sabine in “Magnetical and Meteorological Observations”, Vol. 1. Cape of Good Hope. The period over which the observations extend is unavoidably limited so that it is impossible to say whether the results obtained are truly representative of a whole eleven‐year period.
Note on the present position of the Earth's magnetic axis derived from declination data alone
Authors: van Bemmelen W.
Published: February 2008

The marked secular variation to which the magnetization of our planet is subject, makes it extremely probable, that its mean magnetic axis is also slowly changing its position.

Our exact knowledge concerning this question is almost nil, because we only possess determinations for two epochs, differing but fifty‐six years in time, viz.:Epoch. Latitude. Longitude. Authority.1829,. 78° 16′ N 295° 15′ E Erman and Petersen.1885, . 78 34 291 30 Schmidt.
Die magnetische Observatorien des Preussischen Meteorologischen Instituts
Authors: Schmidt Adolf
Published: February 2008

Das magnetische Observatorium zu Potsdam bildet mit seiner seit Beginn dieses Jahres tätigen Aussenstation bei Seddin (s. Terr. Magn. Vol. XII, p. 79) eine Abteilung des Preussischen Meteorologischen Instituts (Direktor G. Hellmann, vorher W. von Bezold, †17. Feb. 1907, s. T. M. Vol. VL, p. 144), der zugleich die magnetische Landesaufnahme übertragen ist. Gegründet wurde, es 1889 als Teil des meteorologischmagnetischen Observatoriums zu Potsdam (Vorsteher A. Sprung, der auch die Aufsicht über den 1888 beginnenden Bau führte), geleitet zuerst von M. Eschenhagen (†12. Nov. 1901, s. T. M. Vol. VII, p. 77), der die innere Einrichtung und die eigenartige Ordnung des Betriebs schuf, und nach seinem Tode, bis Ende September 1902, vertretungsweise von J. Edler († 2. Juli 1905, s. T. M. Vol. X, p. 192). Die regelmässigen Beob. achtungen begannen am 1. Januar 1890.
Concerning publication “Caractère magnetique de chaque jour”
Authors: van Everdinger E.
Published: February 2008

M. LE DR. MAURITS SNELLEN, ancien directeur à l'Institut météorologique à De Bilt, venant de mourir, nous avons l'honneur de vous faire savoir que, par suite d'une décision du Bureau exécutif de la Commission Internationale de Magnétisme Terrestre, l'Institut météorologique royal des Pays‐Bas se chargera de la publication du, Caractère Magnétique".

Nous vous prions donc de bien vouloir envoyer vos listes du caractère magnétique à
Some microseismic tremors and their apparent connection with barometric variations
Authors: Burbank John E.
Published: February 2008

In 1874 Professor Rossi of Rome, in “Bulletino del Vulcanismo Italiano, Vol. 1,” called attention to a possible connection between microseismic motion and variations in atmospheric pressure. He stated that no marked barometric depression had occurred during the preceding three years without having been immediately preceded, accompanied, or followed by marked microseismic motion.2 Professor Rossi calls these effects baro‐seismic.

The most recent papers on this subject, and the only ones to which I have had access, are those of Professor F. Omori, the well‐known Japanese seismologist.3 Professor Omori has called these motions “Pulsatory Oscillations”, on account of their regular pulse‐like nature.
Störmer's work on the physics of the aurora
Authors: Nutting P. G.
Published: February 2008

With the recent advances in our knowledge of luminescence and electrical effects in rarified gases, hypotheses of auroral formation have become fewer in number and more specific in detail. The spectroscope and transit long ago showed that the aurora is an excitation to luminescence of the upper portions of the Earth's atmosphere. Further study with the spectroscope showed that the luminescence is such as could be caused only by a bombardment of cathode rays, corpuscles, or negative electrons, whatever they may be called. If the light had been caused by a steady current of electricity or by an electric wave it would be reddish orange instead of bluish white in color and would exhibit an altogether different spectrum.
The magnetic character of the year 1906
Authors: van Everdingen E.
Published: February 2008

The first annual review of the “Caractère magnétique de chaque jour”, published on behalf of the International Magnetic Commission by the Dutch Meteorological Institute (see “Terrestrial Magnetism”, v. X, p. 117 and v. XII, p. 183) has appeared.

An introduction states that the number of observatories partaking in this work increased during 1906 from 15 to 35; complete data are available for 30 observatories.
Magnetic observations
Authors: Skey Henry F.
Published: February 2008

The magnetic observers were, in general, Dr. C. C. Farr and Mr. H. D. Cook for the Auckland Islands, and Messrs. H. F. Skey and K. Kidson for the Campbell Islands.

At Enderby Island and Mt. Faye it was impossible to determine the azimuth as the sky was obscured. These declinations could however be calculated at a future date from the observations of the magnetic axis and reference marks (permanent), which were taken. At the stations where only one needle was used to determine the dip, a correction has been applied. The Horizontal Intensity, as determined by N. A. B. C. magnetometer, requires a correction of—.00013 C. G. S., to be applied to reduce to Observatory Standard, (mag 'r No. I). Dips observed with “Field Circle” require a correction of +4.′5 to bring them to the Observatory Standard, (Circle 147; 3 needles).
On the distribution of magnetism over the Earth's surface: 2.
Authors: Passalskij Paul T.
Published: February 2008

Each magnetic element, as well‐known, is undergoing continually changes, some periodic, others aperiodic. Some changes, like the secular variation, considerably affect with lapse of time the value of an element. During the period necessary for conducting a magnetic survey of a district, the observed elements at any point may change, hence, appreciably. It is therefore important to define what values are to be considered as those of the magnetic coordinates of a given point.
The launching of the “Carnegie”, June 12, 1909
Authors: Bauer L. A.
Published: February 2008

The morning of the eventful June 12th dawned fair, though later a slight cloudiness overspread the sky, proving a grateful shield from the fierce rays of the Sun.

The buildings near the entrance of the ship yard of the Tebo Yacht Basin Company (the builders of the “Carnegie”) at the foot of 23rd street, Brooklyn, N.Y., and the vessels in the harbor were gayly decorated in honor of the occasion. It was estimated that from 3,000 to 4,000 people had gathered to witness the launching.
Magnetic storm of September 25, 1909, as recorded at the Cheltenham Magnetic Observatory
Authors: Burbank J. E.
Published: February 2008

All times given in this article refer to eastern or 75th meridian mean civil time; hence in order to get Greenwich mean time, 5 hours are to be added.

The first indication of the storm appeared on the magnetograms obtained at the Magnetic Observatory of the United States Coast and Geodetic Survey, situated at Cheltenham, Maryland, latitude 38° 44′.0 N., longitude 76° 50.′5 W., at 3h 27m a.m., on September 25th, and consisted of a slight increase in both declination and horizontal intensity. It continued as a moderate disturbance until 6h 39m, when the principal portion of the disturbance began and lasted until about 16h.
Northern lights and Earth currents observed by the “Carnegie” in September, 1909
Authors: Peters W. J.
Published: February 2008

The curve is a tracing of as much of the Eschenhagen declination curve as could be seen and where the Eschenhagen curve was indistinct or missing the curve was filled in by means of the Adie eye‐readings properly reduced to correspond with the Eschenhagen base lines. Where Adie eye‐readings are used they are indicated by a small star. Broken lines indicate probable movement of the spot of light.

The small letters a and b refer to the Adie eye‐readings made, respectively, at 8h and 8h 05m, as given in the table.
The magnetic storm of September 25, 1909, at De Bilt, near Utrecht, Holland
Authors: van Dyk G.
Published: February 2008

At De Bilt the magnetic variations are at present recorded in two auxiliary buildings, since the observatory for variation observations, burnt down in 1902, has not yet been built up again. In one of them, the variometers of D, H, and V are placed behind each other, the registration occurs by means of a Toepfer registering apparatus and lamp, the paper is 20 cms. broad, and an hour corresponds to 20 mms. on the base line. In the other building the three elements are recorded apart on three cylinders of an Adie magnetograph, the paper is 12 cms. broad, an hour corresponding to 15 mms. of base line. Here the manner of illumination is different from the usual one.
The complete magnetic results of the first cruise of the “Carnegie,” 1909–10
Authors: Bauer L. A. , Peters W. J.
Published: February 2008

Preliminary results of the magnetic observations made on the portion of the cruise from New York to Falmouth were published in the weekly periodical, Nature, for October 28, 1909. We can now give a summary of the chief results obtained for the entire cruise covering about 8,000 nautical miles and extending over the period from September 1, 1909, to February 13, 1910. The ports visited were Gardiner's Bay, Long Island; St. John's, Newfoundland; Falmouth, England; Funchal, Madeira; and the Bermudas, whence the vessel returned to Brooklyn, New York. The cruise will be found charted in red on Plate II.
Die Werte der erdmagnetischen Elemente in Apia, 1905–1908 (nach den Registrierungen des Samoa‐Observatoriums)
Authors: Linke Von F. , Angenheister G.
Published: February 2008

Im Anschluss an die deutsche Südpolarexpedition wurde im Jahre 1902 von der Kgl. Gesellschaft der Wissenschaften zu Göttingen die Gründung eines geophysikalischen Observatoriums in Apia (Samoa‐Inseln) veranlasst. Das Arbeitsprogramm des Observatoriums umfasst seismische, luftelektrische, meteorologische Arbeiten, und vor allem auch die vollständige Registrierung der drei Elemente der erdmagnetischen Kraft. Die Registrierung wird in angemessenen Zeiträumen (etwa wöchentlich) durch absolute Messungen kontrolliert.
Die Verteilung der Leitfaehigkeit der Atmosphaere ueber dem grossen Ozean, nach den Beobachtungen der “Galilee”
Authors: Nippoldt Von Dr. A.
Published: February 2008

Von Mitte August 1907 bis Mitte Mai 1908 hat der Observator P. H. Dike des Department Terrestrial Magnetism an der Carnegie Institution eine grosse Zahl von Messungen der luftelektrischen Leitfähigkeit der Atmosphäre über dem grossen Ozean auf em damaligen Vermessungsschiffe—die Galilee—angestellt. Er berichtet darüber in dieser Zeitschrift in der Septembernummer 1908, Seite 119 bis 128. Die Ergebnisse werden besonders auf den Einfluss der meteorologischen Elemente untersucht; es lassen sich jedoch noch weitere Schlüsse daraus ziehen, und zwar vor allem auf die Verteilung der Leitfähigkeit über den Ozean hin. Hierbei scheint sich trotz der zum Teil sehr weiten Entfernung zum Lande die Leitfähigkeit dennoch als durch die Landverteilung beeinflusst herauszustellen.
Determination of the pole distance of a very small magnet (abstract)
Authors: Miller J. M.
Published: February 2008

If two circular coils, which are linear single turns, are adjusted so that they are coplanar and concentric, and if two currents are sent in opposite sense around the coils, the two magnetic fields will annul each other at the common center if the ratio of the two currents is equal to the ratio of the radii of the two coils. This gives a method of comparing the radii of coils experimentally. In such a comparison the neutralization of the two fields is usually indicated by a short magnetic needle which is suspended at the common center of the two coils and lies in their common plane.

On account of the finite length of the magnet an error is introduced into the comparison equal to 3/4 K where K is a known function of the pole distance of the magnet and the radii of the coils. If, however, the needle is rotated by torsion or otherwise, out of the plane of the coils, the ratio of the neutralizing currents is changed by a factor 15/4 K sin2a where a is the angle through which the magnet has been rotated. Hence by measuring the angle a and also the change in the ratio of the neutralizing currents, K can be determined, and from this the pole distance of the magnetic needle can be calculated.
Results of some long series magnetic observatory observations: Colaba (1846–1905), Pola (1847–1909), and Potsdam (1892–1900)
Authors: Hazard D. L.
Published: February 2008

Magnetic work at Colaba was started in 1840, but it was not until 1846 that a regular system of observing was adopted. From that time to March, 1906, there is an unbroken series of observations. Photographic registration began in 1872. Prior to that time eye‐readings were taken every hour except on Sundays and holidays.
Request for data
Authors: Stenquist D.
Published: February 2008

The undersigned respectfully requests that papers and not yet published observations of earth‐magnetic and air‐electric phenomena, purple light, halos, coronae, luminous night‐clouds, aurora borealis and australis and zodiacal‐light for June 30 to July 1, 1908, September 25, 1909, and May 19, 1910, be sent to him.