bluuebunny/crossref_metadata_2025 huggingface dataset:
Near‐axial backscattering from a cone‐sphere
Authors: Choi J. , Wang N. , Peters L. , Levy P.
Published: February 2008

The near‐axial backscattering from a conducting cone‐sphere is studied using the equivalent current concept based on the uniform geometrical theory of diffraction (UTD). The creeping waves associated with the spherical base and the conical surface are incorporated into the equivalent current technique. It has been found that the contributions from the creeping waves associated with the conical surface are significant for the oblique incident case. To the best of our knowledge, this is the first UTD approach to calculate the off‐axial backscattering from a conducting cone‐sphere.
Sources of high‐mid‐latitude scintillations in the American zone at 53°N∧
Authors: MacDougall John W.
Published: February 2008

Observations of scintillations for 5 years at about 53°N∧ have been used to attempt to identify the sources of the kilometer‐scale irregularities in this region. The scintillation observations show that there are long‐time, and possibly seasonal variations, which are associated with magnetic activity. The diurnal variation of scintillations shows a nighttime maximum. This occurs before midnight in summer and about 3 hours postmidnight the rest of the year. The correlation of scintillations and magnetic activity is positive in winter, negative in summer, and uncorrelated in equinox. In order to explain these observations, at least three sources of irregularities are required: (1) A local source which is active at sunset in summer. (2) A source at higher latitudes; the irregularities are convected south during nighttime to 53°N∧. This source is most prevalent in winter. (3) A local source which is active over intervals of a few days and may be associated with plasmapause phenomena such as stable auroral red arcs.
Measurement of a zonal wind profile on Titan by Doppler tracking of the Cassini entry probe
Authors: Atkinson D. H. , Pollack J. B. , Seiff A.
Published: February 2008

As the Cassini probe enters and descends through the Titan atmosphere, the winds will cause perturbations to the probe local horizontal velocity resulting in an anomalous drift in the probe location and a measurable shift in the frequency of the probe telemetry due to the Doppler effect. By using an iterative algorithm in which the time variation of the probe telemetry frequency is monitored throughout the descent and the probe trajectory is updated to reflect the effect of wind on the probe location, a highly accurate relative wind profile can be recovered. Coupled with a single wind velocity measured at a known altitude by independent means, an absolute profile results. The accuracy with which the wind profile can be recovered is primarily limited by the a posteriori uncertainties in the probe and orbiter trajectories and oscillator frequencies. An unmodeled drift in oscillator frequency will cause a time‐varying frequency that is inseparable from Doppler effects. Similarly unmodeled changes in the probe‐orbiter relative geometry will lead to Doppler frequency contributions that are indistinguishable from the wind signature.
SCIDAR/radar simultaneous measurements of atmospheric turbulence
Authors: Vernin Jean , Crochet Michel , Azouit Max , Ghebrebrhan Ogubazghi
Published: February 2008

During eleven nights, two different instruments, a scintillation detection and ranging (SCIDAR) and a radar, were simultaneously operated to retrieve profiles of the atmospheric turbulence C2N(h). The SCIDAR spectral window lies between 5 cm and 25 cm, whereas the radar is sensitive to 3.3‐m wavelength. The profiles deduced from the SCIDAR and from the oblique (13°) radar agree fairly well, at least above 9 km, where the effects of specific humidity on radar returns are negligible. On eight occasions the agreement is good enough, over a large range of altitudes, to confirm the validity of Tatarski's theory of beam propagation, Kolmogorov's spectral laws, and Ottersten's description of radar returns.
Echo power loss with RASS (radio acoustic sounding system) due to defocusing effects by distorted acoustic wave front
Authors: Masuda Y. , Awaka J. , Okamoto K. , Tsuda T. , Fukao S. , Kato S.
Published: February 2008

We have calculated the intensity of RASS (radio acoustic sounding system) echoes scattered by refractive index fluctuations produced by acoustic waves. Because of temperature changes in the atmosphere, the sound speed decreases in the troposphere and the shape of the acoustic wave front becomes elliptical. When the shape of acoustic wave fronts is significantly distorted from a sphere, the backscattered radio wave does not focus on the radar. Consequently, the spot size of the RASS echo becomes large, and the peak intensity of the RASS echoes decreases. We numerically estimated the echo power loss due to defocusing effects for an atmosphere whose sound speed decreased linearly with altitude. The loss was found to be a function of the range, radar beam width, radar wavelength, and degree of distortion of the acoustic wave front. When the temperature gradient is 5° C/km, the echo power loss at a range of 10 km for 50‐ and 500‐MHz radars becomes as large as 0.5 and 16 dB for radar beam width of 2.0°, and 7.0 dB and 19.0 dB for a 5.0° width, respectively.
Signal processing and data analysis in middle atmosphere radar
Authors: Rastogi Prabhat K.
Published: February 2008

Use of signal‐processing and data analysis methods in radar studies of middle atmospheric motions is examined. Detection of weak Doppler‐shifted signals from thin atmospheric regions in a noise background requires an optimum receiver. It is noted that the optimum receiver is implemented in successive stages using matched‐filter and correlator structures for locating targets distributed in range and a filter bank for estimating their Doppler shifts. Effectiveness of coherent integration in reducing high data rates, and as an efficient but crude low‐pass filter, is discussed. Use of noiselike binary phase codes and decoding in improving range resolution is outlined. Spectral analysis of radar signals using a time‐averaged periodogram and the autoregressive model is briefly reviewed. Methods of reducing undesirable artifacts in spectral analysis of nonstationary signal components, using windows and trend removal, are delineated. Estimation of signal parameters through spectral moments and least squares estimation is summarized. Finally, simple ad hoc data‐editing methods for suppressing outliers and interference are outlined.
Effect of signal path distortions on the decoding performance in a pulse compression radar system
Authors: Patro Y. G. K. , Nair K. R. Suresh , Balamuralidhar P.
Published: February 2008

Computer simulation studies have been conducted on the range side lobe performance of a pulse compression radar system which uses a complementary biphase‐coded signal transmission. Such a coding scheme is widely used in mesosphere‐stratosphere‐troposphere (MST) radars expecting to achieve ideally zero range side lobes to ensure unambiguous detection of signals. However, system parameters, like overall system bandwidth, delay distortion, limiting, amplitude and phase droop within the pulse, can lead to spillover of a target return into adjacent range bins by raising the range side lobe level. The results of the study indicate that a goal of 20‐dB range side lobe level can be achieved with matched filter bandwidth and reasonable levels of amplitude and phase distortions in the signal path.
Detection and characterization of geomagnetic pulsations using HF ionospheric heating
Authors: Lee H. S. , Ferraro A. J. , Olson J. V.
Published: February 2008

This paper describes the geomagnetic pulsations observed at the high‐latitude ionosphere during the experiment dealing with the ionospheric generation of ELF/VLF electromagnetic waves. The experiments were conducted in June and October of 1987, and there was clear evidence of geomagnetic pulsations intermixed with the ELF/VLF signals generated. This was manifested in both the magnitude and phase data. This paper discusses the detectability of pulsations based on the ELF/VLF generation experimental technique and a method of characterizing the pulsation being observed. A simple simulation model is introduced to facilitate the interpretation of the data, and the procedure for characterizing the pulsation is described.
Introduction to the Special Issue on Correlations Between Plate Motions and Cordilleran Tectonics
Authors: Beck Myrl E.
Published: February 2008

This special issue contains papers that grew out of the American Geophysical Union Symposium “Models for motion of North America and plates of the Pacific basin, and the tectonic history of the western Cordillera—a search for correlations.” This symposium was held in San Francisco on December 13 and 14, 1982. Forty‐two papers were presented on such diverse topics as plate motion and microplate accretion histories, paleomagnetism of Cordilleran terranes and their displacement histories, the volcanic and plutonic history of the western Cordillera, and the timing of important geological episodes of regional extent (onset of extensional tectonics, onset and termination of episodes of strike slip faulting, etc.). Mechanisms of deformation within the Cordilleran continental margin were also discussed. The reader is referred to Eos Trans. AGU (vol. 63, no. 45, 1982) for the full set of abstracts.
Magnetotelluric soundings and the geological structure and tectonics of the Senegalo‐Mauritanian Basin in northern Senegal, West Africa
Authors: Ritz Michel , Bellion Yves , Flicoteaux René
Published: February 2008

The results of the magnetotelluric soundings provide new insights on the geological structure and tectonics of the onshore Senegalo‐Mauritanian basin in northern Senegal (West Africa). Electrical resistivities can be correlated with the major geological units. In the upper 1000 m, resistivity variations indicate a transition from freshwater saturated sediments near the surface to saline water saturated sediments above the basement. The resistivity of the sediments is dominated by their porosity and the resistivity of the contained fluids. The resistivity of the Cretaceous sediments is unexpectedly low, especially in the western part of the basin. The top of the metamorphic/granitic basement cannot be located on the west portion of the profile because of the feeble resistivity contrast between the impervious, compacted Aptian‐Jurassic limestones and the metamorphic/crystalline rocks. The magnetotelluric estimates of the depth of the basement range from 600 m in the east to 4000 m in the west. Based on the magnetotelluric interpretation and other independent geophysical and geological information, a cross section through the Senegalo‐Mauritanian basin along the magnetotelluric traverse is presented. A zone of high electrical conductivity is observed in the crust, at depths of 4–6 km, on the eastern margin of the deep basin. This conductive structure may be the extension of one further south that was revealed by an earlier investigation. The entire conductive zone, which runs north–south between longitudes 15° and 16°W, may be a major fracture zone related to the opening of the Atlantic Ocean; however, its origin remains to be established.
New model of the midcontinent rift in eastern Minnesota and western Wisconsin
Authors: McSwiggen Peter L. , Morey G. B. , Chandler Val W.
Published: February 2008

The Midcontinent rift contains a central zone of mostly volcanic and associated intrusive rocks. Flanking, and in places overlying, these mafic igneous rocks are clastic sedimentary basins which range in thickness from less than 1.5 km southwest of the west end of Lake Superior to more than 3.0 km near the Minnesota‐Iowa border. New gravity and magnetic modeling of the rift has shown that most of the volcanic and intrusive rocks are contained within a central block, which in Minnesota and Wisconsin extends to a depth of at least 10 to 20 km. The geometry of this central block, which ranges from fairly symmetric to very asymmetric, appears to reflect a change from predominantly a graben to only a half‐graben development. The modeling has also suggested the presence of a major prerift intrusive body along the Minnesota‐Iowa border which could have locally controlled the rift’s development.
Tectonic implications of paleomagnetic data from sills and dykes in the Sverdrup Basin, Canadian Arctic
Authors: Jackson K. C. , Halls H. C.
Published: February 2008

Mesozoic intrusives, 71 sills and 12 dykes, from different structures in the folded eastern Sverdrup Basin contain stable, well‐grouped paleomagnetic directions of both normal and reverse polarity. The mean direction is 274°, +79°, k=173, α95=3.7°, with a corresponding pole position at 157°, 67°N, k=61, A95=6.6°. The paleomagnetic fold test shows that the major deformation, involving tilting of strata around strike, postdated the emplacement of sills and dykes. Minor preintrusion deformation may also have occurred, but, more importantly, an offset of the paleopole from the Cretaceous section of the polar wander path permits a postintrusion anticlockwise rotation of eastern Sverdrup Basin of about 15+/−20° with respect to stable North America. If the intrusives are Cretaceous, the degree of rotation is close to that (11°) estimated for Greenland during the opening of the Labrador Sea. No positive evidence has been found to support models of distributed shear with block rotations to accommodate the contentious northeast translation of Greenland along the Nares Strait.
North American apparent polar wander, plate motion, and left‐oblique convergence: Late Jurassic‐Early Cretaceous orogenic consequences
Authors: May Steven R. , Beck Myrl E. , Butler Robert F.
Published: February 2008

The North American apparent polar wander (APW) path indicates an episode of unusually rapid absolute northward motion of western North America between 150 and 135 Ma. During this time the northward component of absolute motion of points along the Washington‐Oregon‐California coast was in excess of 150 km/m.y. and perhaps as high as 230 km/m.y. We believe that such high absolute northward velocity for North America probably ensures that relative motions of oceanic plates and terranes influenced by them were to the south at this time.

The inception of rapid northward motion and left‐oblique convergence was abrupt and should be recorded in the geology of the western Cordillera. It is tempting to correlate this period of unusual Pacific basin‐North American interaction with the “Nevadan orogeny” in the Klamath Mountains as well as with left‐lateral strike‐slip structures such as the Pine Nut fault and Bear Mountains fault zone. Significant differences exist between North American plate motion recorded by the Late Jurassic‐Cretaceous APW path and that predicted by a fixed hotspot model. We believe that this discrepancy reflects uncertainty associated with pre‐Late Cretaceous hotspot tracks and poorly constrained relative plate motions during the Cretaceous normal polarity superchron.
Uplift of the Sierra San Pedro Mártir Baja California, Mexico
Authors: O'Connor James E. , Chase Clement G.
Published: February 2008

The Sierra San Pedro Mártir of Baja California is the highest of the Peninsular Ranges and has undergone rapid Cenozoic uplift. Recent uplift can be explained as a result of flexural isostasy driven by a previously suppressed crustal root. Two‐dimensional modeling of topography and Bouguer gravity data for present and preuplift conditions indicates that a flexural isostatic mechanism for uplift is consistent with the available topographic, geologic, and geophysical data. The crustal root underlying the batholithic rocks of the Sierra San Pedro Mártir was probably emplaced during Cretaceous magmatic arc activity. However, existence of a vast, low‐relief and low‐elevation erosion surface mantled with deposits of fluvial systems originating far to the east suggests that by the early Tertiary the plutons were unroofed, and there was only subtle topographic expression of this crustal thickening. We model the remnant crustal root as regionally compensated (suppressed) beneath a strengthened and continuous elastic plate and topographically expressed as a broad dome. The regional distribution of Tertiary sediments and preserved drainage patterns are geologic evidence of such doming. Since the late Miocene there has been rapid uplift and apparent drainage reversal near the dome apex. The present topography approximates the predicted isostatic response of a doubly broken elastic plate to the previously suppressed root. Several lines of evidence indicate that a major component of uplift of the Sierra San Pedro Mártir has occurred during the Pliocene‐Quaternary and that the crustal scale faulting that has allowed the range to rise rapidly toward local isostasy is related to full development of the San Andreas‐Gulf of California transform system.
Evolving Early Mesozoic Convergent Margin Deformation, central Klamath Mountains, northern California
Authors: Goodge John W.
Published: February 2008

The Stuart Fork terrane in the central Klamath Mountains of northern California is a coherent Late Triassic blueschist belt which records early plate convergence in western North America. Complex deformation and polyphase metamorphism of the terrane directly reflect evolving convergent margin processes. Two major periods of deformation are recorded in the Stuart Fork terrane: D1, an early (Late Triassic) phase of synmetamorphic deformation which produced complex folds and possible southwest directed reverse faults, and D2, a late stage (mid‐Jurassic) deformation which formed simple, open folds as a result of westward thrusting of the entire terrane over neighboring terranes during regional shortening. D2 thrust imbrication of the Stuart Fork and adjacent terranes also produced a mélange zone characterized by disrupted tectonic slivers of these terranes. Each of these episodes of shortening is related to convergence, and at least one (D1) accompanied high‐pressure blueschist facies metamorphism during subduction. More importantly, however, it is possible to distinguish deformation features which formed during initial subduction from those which formed as a result of final thrusting (or accretion) of the entire assemblage to the continental margin as regional contraction progressed through the arc and forearc region. The Stuart Fork terrane is a lithologically and structurally distinctive lithotectonic assemblage which cannot be directly correlated with other terranes of the western Paleozoic and Triassic subprovince. Nonetheless, the Stuart Fork and other similar terranes of the central Klamath Mountains share a common origin as oceanic materials which were accreted against the continental convergent margin in mid‐Mesozoic time during east directed subduction.
Origin of igneous rocks associated with Mélanges of the Pacific Rim Complex, western Vancouver Island, Canada
Authors: Brandon Mark T.
Published: February 2008

The Pacific Rim Complex (PRC) has previously been interpreted as a late Mesozoic subduction complex that formed along the western margin of Vancouver Island. This paper examines a specific aspect of this interpretation: that igneous rocks within the PRC are fault slices derived from the footwall or hanging wall of a subduction thrust. The footwall would have been an oceanic plate, and the hanging wall, Wrangellia, a large coherent terrane that underlies most of Vancouver Island. New mapping has shown that the PRC comprises a lower Mesozoic volcanic unit, herein named the Ucluth Formation, and a superjacent sequence, more than 2 km thick, of Lower Cretaceous sediment‐rich mélanges. Within the mélanges are large blocks of volcanic and plutonic rocks, most of which were derived from the underlying Ucluth Formation. A minor fraction of these blocks cannot be assigned to Ucluth; they consist of Upper Jurassic pillow basalt and rare ultramafite. Fossil ages and chemical data indicate that the bulk of the igneous rocks in the PRC, as represented by the Ucluth Formation and blocks derived from the Ucluth, could not have come from Wrangellia nor from a subducting oceanic plate. The blocks of Upper Jurassic pillow basalt do represent fragments of oceanic crust, but field relations indicate that they are not fault slices. The mudstone matrix surrounding the blocks contains interbeds of “green tuff” which are shown to be scree deposits derived from the Ucluth and the Upper Jurassic pillow basalts. My interpretation is that the PRC mélanges formed by surficial mass wasting, and not by faulting along a subduction thrust. Furthermore, regional geologic relations indicate that the present location of the PRC, outboard of Wrangellia, is a result of strike slip faulting during the latest Cretaceous or early Tertiary. This event postdates the formational age of the mélanges by at least 45 m.y.

An appendix of chemical analyses, locality descriptions, sample petrography, analytical methods, and estimated accuracy is available with the entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document T89‐004; $2.50. Payment must accompany order.
Paleomagnetism and tectonics of Malaita, Solomon Islands
Authors: Musgrave Robert J.
Published: February 2008

Malaita, in the Solomon Islands, is the emergent expression of the Pacific Province, a geologically distinct suspect terrane which is commonly held to be the margin of the Ontong Java Plateau, a thickened portion of Pacific plate overthrust onto the rest of the Solomon Islands Arc during a late Miocene reversal of the polarity of the arc. Subduction of the Australian plate replaced Pacific plate subduction during this event, and the Solomon Islands Arc was transferred from the Australian plate to the Pacific plate. A paleomagnetic survey of the eastern Solomon Islands included sampling in southern Malaita. Magnetostratigraphic dating gives an age of 5.8 Ma for the Haruta Calcisiltite‐Hada Calcisiltite facies change on Malaita. This facies change resulted from renewed volcanic activity following the initiation of Australian plate subduction. Paleomagnetic poles from two pre‐Pliocene units do not lie near the Pacific apparent polar wander path (APWP), as the conventional model would suggest, but rather fall on the Australian APWP, suggesting that the Pacific Province developed as a part of the Australian plate. Correction for 6.5 Ma of Pacific‐Australia relative motion produces an improved, very close fit to the Australian APWP, consistent with the transfer of Malaita, along with the rest of the arc, to the Pacific plate at about that time. Magnetic paleolatitudes from a DSDP hole on the Ontong Java Plateau, which disagree with usually accepted Pacific Tertiary motion, also fail to match the Malaitan data; the possibility that Malaita could be a part of an Ontong Java sub‐plate, somehow detached from the rest of the Pacific plate, can be discounted. Malaita and the rest of the Pacific Province arose in the fore‐arc of the originally north‐east facing arc. Collision of the Ontong Java Plateau with the trench slowed subduction of the Pacific plate and began subduction of the Australian plate below the arc. Both subduction zones may have been active for a period, beginning at about 10 Ma and ending at about 3 Ma, until Pacific plate subduction broke down, and the Pacific Province was subsequently uplifted and deformed.
Satellite laser ranging and geological constraints on plate motion
Authors: Harrison C. G. A. , Douglas Nancy B.
Published: February 2008

We have analyzed Satellite Laser Ranging (SLR) observed baseline rates of change and compared them with rates determined from sea floor spreading rates and directions, and earthquake solutions. With the number of years of observation now over six for many of the baselines, the inaccuracy of determining baseline rates of change has diminished so that in some cases it is less than a few mm per year. Thus a direct comparison between baseline rates of change and rates of change established using geophysical information (which we call geological rates) is now feasible. In most cases, there is good agreement between the rates determined from SLR and geological rates, but in some cases there appear to be discrepancies. These discrepancies involve many of the data for which one end of the baseline is either Quincy (California), Huahine (French Polynesia) or Simosato (Japan). We have devised a method for looking at the discrepancies for these SLR observatories which allows us to calculate the motion not modelled by the geologic information. The results are discussed in terms of what is known about plate margins, and other information.
Aimantation induite par le champ terrestre sur les aimants
Authors: Mascart Par M. E.
Published: February 2008

Dans la méthode de Gauss, généralement employée pour évaluer la composante horizontale H du champ terrestre, on détermine d'abord le produit P = M H du moment magnétique M d'un barreau par cette composante, à l'aide des oscillations, puis le quotient
au moyen des déviations que le barreau produit sur un déclinomètre.

Dans ces expériences, le moment magnétique du barreau est modifié par l'aimantation induite que produit le champ terrestre; on est d'ailleurs autorisé à admettre que cette aimantation est uniquement temporaire, réversible sans hystérésis, et proportionnelle au champ.
Tafeln zur genäherten Auswertung von Kugelfunctionenreihen und ihren Differentialquotienten
Authors: Schmidt Von Dr. Ad.
Published: February 2008

Im Laufe einer Reihe von Jahren, in denen ich mit Untersuchungen über das erdmagnetische Potential beschäftigt war, habe ich Veranlassung gefunden, mir allmählich eine grössere Zahl von Hülfstafeln zur Erleichterung numerischer Rechnungen anzulegen. Manche davon, so z. B. die hier mitgeteilten, besitzen eine so allgemeine und vielfache Verwendbarkeit, dass ihre Veröffentlichung wohl gerechtfertigt erscheint.

Zur Auswertung einer durch eine Kugelfunctionenreihe dargestellten Function, z. B. eines Potentials V, giebt es bereits verschiedene Tafeln. Ich selbst habe in dieser Zeitschrift (Vol. I, pag. 75, 76) eine kleine Tabelle der Logarithmen der Functionen Rmn mitgeteilt. Diese Hülfsmittel sind indessen noch nicht bequem genug, wenn man, was oft vorkommt, schnell eine wenn auch nur ganz rohe Uebersicht (am besten in graphischer Darstellung) über die Verteilung der Functionswerte auf der ganzen Kugelfläche gewinnen will. Es genügen dann sehr stark abgerundete Werte der Reihencoefficienten und der Kugelfuiictionen. Diese letzteren findet man nun—auf 3 Decimalstellen angegeben—im ersten Teile der umstehenden Tabelle. Rundet man sie, was für den bezeichneten Zweck vollkommen ausreicht, auf 2 Decimalen ab, so kann die Berechnung der Reihe
The beginnings of magnetic observations
Authors: Hellmann G.
Published: February 2008

After Christopher Columbus discovered the magnetic declination, on the 13th of September, 1492—or, as others think, the geographical variation of the same—mariners began to bestow increased attention on the compass.2 Voyages to the West Indies becoming now more frequent, showed that the declination of the magnetic needle from the astronomical meridian, which on the west coast of Europe was easterly, decreased gradually toward the west, vanished in the neighborhood of the Azores, and then passed over into a westerly declination. What wonder, then, that it was thought that in this way the geographical longitude could be determined! Christopher Columbus and Sebastian Cabot had already thought of the possibility of such a solution of this, the most important of the nautical problems of that time, and in the sixteenth century the number of those who sought to ascertain the longitude magnetically increased very materially. The fact that the line of no declination, or the agonic line, almost coincided with the zero meridian as adopted at that time—at least in that part of the Atlantic Ocean traversed by voyagers to the West Indies‐certainly helped not a little to continually strengthen the belief in the possibility of determining the longitude with the aid of the compass. The agonic line was looked upon as a point of departure given by Nature herself for the reckoning of longitude.
Le Cadet's treatise on atmospheric electricity
Authors: McAdie Alexander
Published: February 2008

Dr. Le Cadet has given in this volume of 200 pages a very general review of our knowledge of atmospheric electricity. Specifically, the chief aim of the work is to critically review present theories as to the origin of the electricity of the atmosphere in the light of certain modern determinations of the strength of the earth's electric field. Many years ago Sir William Thomson desired that we might have a general electrical survey, showing the surface density of the electrical charge on the earth's surface. If this were known, we could determine the normal values of the earth's field.
Sur la périodicité des perturbations de l'aiguille aimantée horizontale, à l'observatoire du parc Saint‐Maur
Authors: Moureaux Par M. Th.
Published: February 2008

La série des observations magnétiques faites à l'observatoire du Parc Saint‐Maur remonte au Ier janvier 1883; elle comprend donc actuellement seize années. Les courbes de variations de D, H et Z sont réduites, et transformées en tableaux qui donnent, pour chaque heure, la valeur absolue de ces trois éléments. Le résumé des quinze premières années, qui vient d'être publié, permet ainsi la discussion de 131,496 observations.

Nous n'envisagerons ici que la variation horaire et mensuelle des perturbations de la déclinaison et de la composante horizontale. Ce mot perturbation doit d'ailleurs s'entendre au sens le plus large; il ne s'aplique pas seulement aux grands orages magnétiques; mais à toute valeur horaire s'écartant de sa valeur normale, dans un sens ou dans l'autre, d'une quantité déterminée.
New magnetic intensity‐variometers
Authors: Heydweiller Adolf
Published: February 2008

1. Two like declination needles, one lying above the other, with a common axis of rotation, are brought into such a position that they cross at right angles to each other, each making an angle of 45° with the magnetic meridian; then, on turning the magnets, each of the four poles moves in an almost homogeneous magnetic field, as is apparent from the known distribution of the lines of force of bar magnets, and a change in the exterior directive force, the horizontal intensity of the earth's magnetism, corresponds to a proportional turning of the needles. This is the fundamental principle of the instruments now to be described.

2. Description of a simple local‐variometer for the horizontal intensity. Two rhombic magnetic needles of tungsten steel, 5.7 cm. in length and about 1.4 g. in weight, which, treated according to Strouhal and Barus, possess a magnetic moment of about 30 C. G. S., oscillate on pivots, above dampers of copper plate, in a cylindrical case, with a vertical distance between them of about 6.4 cm., which, by raising and lowering the lower pivot with a screw and a check‐nut, can be varied and can be precisely fixed, The lower needle carries two light aluminum indices, perpendicular to its axis and pointing upward, which move, at the ends of the upper needle, over small graduations on silvered glass attached to it. The turning of the needles relative to one another is determined at different points, and the difference of the readings on each scale for the two positions of equilibrium of the needles, 90° apart, is found. The height of the whole instrument, which rests on three foot screws, is 16 cm., the diameter of the base 15 cm., its weight, 1.5 kg,; it is, therefore, quite portable.
A source of error in the Kew magnetometer
Authors: Morize Henry
Published: February 2008

The Kew magnetometer, No. 134, by Negretti and Zambra, was examined at the Observatory at Kew, and was accompanied by a table of corrections when it was exported from England. In employing the instrument for observations of the declination, I discovered in its construction the existence of a cause of error of a magnitude and character worthy of being pointed out, since it is probably present in other instruments of the Kew pattern. The magnet is observed through a pane of glass, which closes the front of the box in which it is suspended. To find the direction of the astronomical meridian, we hoist the magnet, by means of its suspending thread and sight under it, toward the movable mirror which reflects the rays of light from the sun or from some mark, across the two panes of glass that are employed to close the front and rear of the magnet‐box.
The effect of glass covers in magnetic instruments
Authors: Fischer E. G.
Published: February 2008

Some time in the winter 1896–7, while determining index corrections of the compass declinometers belonging to the Coast and Geodetic Survey, Assistant G. R. Putnam observed motions of the magnetic needles of such nature as to leave no doubt that the glass covers of these instruments carried strong electrostatic charges, caused by atmospheric conditions, which at the time were especially favorable, the weather being dry and cold.

In two of the declinometers, in which the glass covers were afterwards replaced by brass plates, with only small pieces of glass covering the openings through which to observe the points of the needles, no erratic movements were noticed, and repeated determinations of their index corrections, agreed with each other within the error of observation; while, before, nearly all observers using these instruments reported occasional discrepancies in their results, which could not be accounted for.
Einige bemerkungen zur messung der horizontal‐intensität des erdmagnetismus mittels des magnetischen theodoliten
Authors: Liznar J.
Published: February 2008

Unter den Methoden, welche zur Messung der Horizontal‐Intensität des Erdmagnetismus angegeben worden sind, hat jene mittels des magnetischen Theodoliten die häufigste Anwendung gefunden, ja man kann sagen, dass sie an den magnetischen Observatorien nicht nur für die fortlaufenden Beobachtungen, sondern auch bei den magnetischen Aufnahmen ausschliesslich im Gebrauche ist. Bei dieser Methode wird bekanntlich die Schwingungsdauer eines Magnetstabes und jener Winkel, um welchen er einen in derselben Horizontalebene liegenden, kleineren Magnet ablenkt, beobachtet, wobei die Längenaxe des ablenkenden senkrecht steht zu der des abgelenkten und deren Verlängerung letzteren in seiner Mitte trifft.
Some recent contributions to terrestrial magnetism
Authors: Bauer L. A.
Published: February 2008

During the past five years a most remarkable interest in magnetic work has been shown throughout the civilized world. The present time can well be likened to the years when Gauss inaugurated a Magnetic Association, consisting of investigators from all countries, in order to carry out observations simultaneously at stated periods, for the purpose of deducing laws governing the complex phenomena of the Earth's magnetism, and to recognize harmony in irregularities apparently subject to no law.

Almost every civilized country has either just completed a magnetic survey, or is taking the necessary steps for the inauguration of such work on a grander and more comprehensive scale than ever before.
Nachtrag zur Mittheilung: einige bemerkungen zur messung der horizontal‐intensitæt des erd‐magnetismus mittels des magnetischen theodoliten
Authors: Von J. Liznar
Published: February 2008

In einer Mittheilung in No. 2 dieses Bandes habe ich den Vorschlag gemacht, bei den Messungen mit den magnetischen Reise‐Theodoliten die Ablenkungswinkel in zwei Distanzen zu bestimmen, weil sich dann mit Hilfe der beiden Ablenkungswinkel der richtige Wert der Grosse C (der Gleichung 6) immer ermitteln lässt. Da aber die Methode, welche ich am Schlüsse der pag. 64 zur Berechnung von C″ angeführt habe, nur einen rohen Näherungswert
liefert, wovon man sich leicht durch die daselbst angegebenen Substitutionen überzeugen kann, so sei es mir gestattet, auf diesen Gegenstand nochmals zurück zu kommen, um zu zeigen, wie der jedesmalige Wert von C genau zu berechnen ist.

Es muss zunächst betont werden, dass die am Anfange der pag. 69 aufgestellte Behauptung : die relative Grösse und die Form der Magnete sei gleichgiltig, nicht aufrecht gehalten werden kann, sondern dass vielmehr die relative Göosse der Magnete an die Bedingung geknüpft ist, dass in der Reihe

urn:x-wiley:00968013:media:tma381:tma381-math-0002
die Grösse Q=o wird.
Notes on some recent contributions to atmospheric electricity
Authors: McAdie Alexander
Published: February 2008

Elster and Geitel1 have shown that normal air contains positive and negative ions in nearly equal quantities and that these ions are free to move in ordinarily pure air. In damp air their mobility is not so marked. The ionic condition of gases first investigated by W. Geise2 in 1882, has been used by Elster and Geitel as a basis of the theory explaining the origin of the electrification of the atmosphere. Zeleny3 showed that the negative ions as a rule have the greater mobility.
Results of some recent magnetic investigations in Italy
Authors: Littlehales G. W.
Published: February 2008

It is indispensable in laying the foundation for researches into the distribution of values of the terrestrial magnetic elements that observations should extend to all parts of a region, whether the terrain does or does not exert a sensible local action.

For example, one who would determine the values of the constants of terrestrial magnetism on the island of Elba, or in the volcanic terrain of Latium, or among the serpentine and dioritic rocks of the Alps, or, in general, anywhere in the midst of the magnetic masses, would do his work in vain; because, firstly, by repeating the observations in the same locality, but at points slightly distant from those previously occupied, he would obtain probable values differing much from those obtained at the first points; and, secondly, the electric discharges in the atmosphere would more or less modify the magnetic conditions of the ground.
Summary of results of recent comparisons of magnetic instruments
Authors: Bauer L. A.
Published: February 2008

During the fall of 1899 I compared a set of the Coast and Geodetic Survey magnetic instruments with the standard instruments at Kew (England), Potsdam (Germany), Pavlovsk (Russia), and Pare St. Maur (France). I also compared, the dip circle with Schering's earth‐inductor at Darmstadt, Germany. The comparisons were made at Kew both before and after those at the other places named. It had been the original intention to begin and end the comparisons at the Toronto Magnetic Observatory; however, circumstances over which I had no control prevented the carrying out of this idea.
Some experiments upon the relations between ether, matter, and electricity
Authors: Gilbert Norman E.
Published: February 2008

In the following paper are described a number of experiments, undertaken at the suggestion of Professor H. A. Rowland, upon the relations between ether, matter, and electricity. The theories advanced in the paper as suggestive of the experiments are, to the best of the writer's ability, statements of Professor Rowland's ideas. Unfortunately the sudden illness and death of Professor Rowland prevented him from reviewing the paper.

Since the development of the wave theory of light by Huygens in 1678, the most important problem which has confronted the physicist has been the determination of the nature and the properties of the medium which we must imagine to fill all space for the propagation of the waves which give rise to the sensation of light. Numerous ethers have been postulated, each with properties which might account for the phenomenon under consideration, but none of which have made any claim to universal application. Green has developed extensively the elastic solid theory, and has even made estimates of the density and rigidity of the ether. The recent development of the electro‐magnetic theory of light and the location of the electro‐magnetic energy in the ether have demanded properties entirely different from any which could be furnished by a rigid elastic solid, and new ethers have been postulated accordingly. Faraday's discovery of the rotation of the plane of polarization of light in a magnetic field suggested that the particles of matter, or the ether in connection with them, must be in rotation. As a result of the theories proposed by Ampere and Weber, and developed by Maxwell, modern theories of magnetism are based on some kind of rotary or vortical motion in the ether, and if a piece of iron is magnetized, we imagine that the molecules, or something about them, rotate also. Maxwell has tried to detect the presence of any such rotation in an electro‐magnet. With a kind of gyroscope he showed that, if it exists, the angular momentum must be small compared with any quantities which we can measure. An attempt was made, at the suggestion of Professor Rowland, by Mr. Paul McJunkin and the author, to determine within what limit it is possible to say that there is no frictional or viscous resistance in the ether connected with such rotation.
Report on the magnetic observations made during the total solar eclipse, May 17–18, 1901, at the magnetic observatory, Potsdam, Germany
Authors: Eschenhagen Max
Published: February 2008

Besides the regular magnetic registrations of the Observatory, the following additional work was done in response to the appeal for international co‐operation in the special magnetic work on the day of the eclipse:

A. Eye readings of the unifilar and bifilar magnetometers and of the balance every minute from 14h 37m to 22h 30m Greenwich mean astronomical time, May 17, 1901, the observers being Messrs. Lüdeling, Edler, Nippoldt, Bidlingmayer, Luyken, Warthmann, and Ott. The bifilar magnetometer was read on the full minute, the unifilar 10 seconds before, and the balance 10 seconds after, all by the same observer. The reduction formulae, the values of the base lines being provisional, are:

D = 10° 01′.2 W‐1′.0 (n‐150),

H = 18830 + 2.63γ (n′‐60) + 3.35γ (t′‐20°),

Z = 43470 + 3.1γ (n″‐100) − 2γ (t″‐20°)
Report on the magnetic observations made during the total solar eclipse, May 17–18, 1901, at the Royal Alfred Observatory, Mauritius Island
Authors: Claxton T. F.
Published: February 2008

I have much, pleasure in forwarding contact prints of the magnetograph traces (Adie system) obtained during the total solar eclipse of May 18, 1901. The value of 1mm of ordinate is for D, 1′.117, for H, 2.66), and for Z, 7.7γ. It will be observed that the sensibility of the horizontal intensity trace is about double that recommended by the British Association for the Advancement of Science, and on the originals slight tremors are seen between 7:15 and 7:50 and occasionally between 8:05 and 9 A.M. Mauritius mean local times, the corresponding Greenwich mean astronomical times of May 17 being, respectively, 15:25 to 16:00 and 16:15 to 17:10.
Description of a set of magnetographs designed by W. Watson
Authors: Watson W.
Published: February 2008

Some time ago I designed a set of magnetographs to be used in determining the disturbances produced by an electric railway on the three magnetic elements, the experiments being made with the view to the framing of regulations for the protection of the English magnetic observatories. Since observations had to be made at a number of stations, and accommodation for the instruments was often very rough, generally stables and sheds, it was essential that the instruments should be easily and rapidly set up and adjusted, also that they should not require a darkened room. Captain Fraser, the director of the magnetic survey of India, having seen these instruments, asked me to design a set on similar lines for use at the four base stations of that survey, and although I can not claim any novelty for the arrangement as a whole, yet it has been suggested to me that a short description of the instruments might be of use to others who have to design such instruments.

No attempt is to be made in the case of the Indian magnetic survey to keep a record of the changes in the vertical component, and thus in the attached photographs, which were taken from the Indian instruments, only the declination and horizontal intensity instruments are shown. Some photographs of the vertical intensity balance used in England have, however, been added.
Ueber den Einfluss der Spiegel‐Collimation bei Spitzen‐Aufhaengung auf Declinations‐Messungen
Authors: Haussmann K.
Published: February 2008

Die Annahme, dass der Collitnations‐Fehler eines freischwingen den Declinations‐Magnets durch das Umlegen in Wegfall komme, gilt nur für den Fall, dass die Verbindung s‐Linie der zwei Aufhänge‐Puncte durch den Schwerpunct des Magnet‐Systems geht. Für die Aufhängung an einem Faden ist dies leicht zu bewirken, nicht aber für die Bewegung auf einer Spitze.

1) Bei der Pinnen‐Auf hängung ist die genannte Forderung (Schwerpunct in der Verbindungs‐Linie der beiden Aufhänge‐Puncte) erfüllt, wenn die Axen der Ausschleifungen des Doppel‐Hütchens zusammenfallen mit der geometrischen Axe der Fassung des Hütchens, bez. der Axe der Hülse, in der das Doppel‐Hütchen sich bewegt Allgemein trifft die Forderung noch zu, wenn die Axen der Ausschleifungen des Doppel‐Hütchens parallel und symmetrisch zur Axe der Fassung liegen und der Schwerpunct in beiden Lagen gleich tief unter dem Auf hänge‐Punct liegt. Zu diesen Voraussetzungen für die Construktion kommt noch die weitere für die Messung, dass der Magnet in seinen beiden Lagen genau centrisch auf die Pinne gesetzt wird, oder wenn dies aus mechanischen Gründen nicht möglich ist, dass die Pinne zwischen beiden Magnetlagen um 180° gedreht werde, bei genau gleicher räumlicher Lage des Magnets.
The Christchurch Magnetic Observatory, New Zealand
Authors: Farr C. Coleridge
Published: February 2008

The Observatory is situated in the Christchurch Botanical Gardens, in latitude 43° 31′ 50″ S.; longitude 172° 37′ 18″ E. The time employed in New Zealand is that of longitude 172° 30′ 00′′ E., or 11h 30m E., and when Greenwich time is not stated as being adopted, it is this local .standard time which is used at the observatory.

The observatory consists of three buildings, situated sufficiently far from one another for the operations carried on in one to be without appreciable effect in the others. The “absolute house” and “variation house” are both constructed of material which has been tested and found rice from magnetic effect. The absolute house is built of wood fastened with copper nails and brass screws; the roofing is of slate.
An analysis of the results from the Kew magnetographs on quiet days during the eleven years 1890–1900, with a discussion of certain phenomena in the absolute observations
Authors: Chree Charles
Published: February 2008

The late Kew Observatory Committee joined in 1890 in a scheme whereby five days each month were to be selected as magnetically quiet days by the Astronomer Royal, with a view to the curves on these days being tabulated by observatories which did not care to undertake the tabulation of every day's curves. That scheme has been persisted in, and the present paper deals with the results it has led to during the eleven years 1890–1900. The paper treats of the secular change in the several elements, of the annual inequality, of the diurnal inequality, and the non‐cyclic effect in the diurnal variation. Attention is more particularly given to the declination, inclination, and the horizontal and vertical components, but some consideration is also given to the northerly and westerly components of the horizontal force and to the total force.
Results of the magnetic observations in the United States up to June 30, 1902
Authors: Bauer L. A. , Hazard D. L.
Published: February 2008

Two recently issued publications bring the results of the magnetic (declination, dip, and intensity) in the United States up to the date June 30, 1902.

The “Magnetic Declination Tables for 1902,” cited in the foot‐note below,1 is a continuation of the series of papers begun in 1855, treating of the magnetic declination in the United States, the last one published having been by the late Mr. Schott in the year 1897 and giving the results for 1900. The form of publication has been altered into the more convenient octavo form.