Microstructures of High-grade Metamorpbic Rocks at Broken Hill, Australia

Frequency distributions of true interfacial angles in high-grade,regional metamorphic rocks from Broken Hill indicate that interfacialtension varies with relative crystallographic orientation incommon minerals. In some single-phase aggregates (e.g. quartz,feldspar, garnet, and calcite) the grains are equant and polygonal,anisotropy of interfacial tension having only a small effecton the appearance of such aggregates. This is also true of two-phaseaggregates of these phases, but their appearance is complicatedby the presence of inclusions, the relative proportions of ihephases, and the characteristic dihedral angle formed by a grainof one phase in contact with two grains of the other. In phases for which interfacial tension is more orientation-dependent,crystal forms exert some control on the appearance of the microstructure.For example, in hornblende and pyroxene aggregates, some interfacesare parallel to planes of the form {110}, although most areirrational. In still more anisotropic phases, low-energy forms(e.g. {001} of biotite and {110} of sillimanite) are very stable,giving rise to a predominance of planar, rational boundariesover curved, adjustment boundaries. Anisotropy of interfacial tension is expressed in the shapesof inclusions. However, even where strongly anisotropic mineralsare involved, inclusions with partly planar boundaries occuralongside inclusions with completely curved boundaries.     

THE COMPUTATION OF SINGLE STRIPS IN PLAN

This paper discusses a simple method of computing independent strips under certain reasonable approximations. It is shown that, if the method is regarded as if it were computation by polynomials, the order of the polynomial is decided by the nature of the control provided and not by the number of controlled models. This conclusion should throw some light on the vexed (and perennial) problem of the choice of orders for polynomials.     

Ergebnisse von Temperaturmessungen im Gemünder Maar/Eifel

Zusammenfassung Auf Grund von Messungen im Gemünder Maar/Eifel in den Jahren 1959 und 1960 wird der Jahresverlauf der Temperatur in verschiedenen Tiefen und das Verhalten der Sprungschicht diskutiert. Zusammen mit Registrierungen der Globalstrahlung in Köln ergibt sich ein Einblick in den Wärmehaushalt des Sees.

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Summary Based on measurements in the Gemünder Maar/Eifel during the years 1959 and 1960, the annual variation of water temperature in different depths and the behaviour of the discontinuity layer (thermocline) are discussed. Taking into consideration records of global radiation in Cologne, and estimation of the thermal economy of the lake is possible.

     

Magnetic pinch in relation to the lightning stroke

Summary The application of the snow plow approximation to the magnetic pinch effect in the return stroke of lightning is described. Results are presented for a constant electric field and for a measured stroke current. In general, the solutions indicate that the magnetic pinch effect is important for cases of high currents, small channel diameters, and low degrees of ionization.     

Evaporation and radiation heat balance at the soil surface

Summary Evaporation from an area covered with short clover-grass has been determined by means of evapotranspirometers (4 m²), open (12 m²) and screened (1/3 m²) evaporimeters, and it has been estimated on the basis ofPenman's andThornthwaite's theories, too. The results of the measurements with the various instruments are compared with each other and with the results derived from the cited theories.Further, radiation heat balances have been made, including evaporation and heating of soil and atmosphere.

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Zusammenfassung Die Verdunstung über einer mit kurzem Kleegras bedeckten Fläche wurde mittels Evapotranspirometern (4 m²), offenen (12 m²) und abgeschirmten (1/3 m²) Evaporimetern gemessen und auch auf Grund vonPenmans undThornthwaites Theorien berechnet. Die Meßergebnisse der verschiedenen Instrumente werden untereinander verglichen und auch den mittels der angeführten Theorien abgeleiteten Resultaten gegenübergestellt.Weiters wurde eine Strahlungs-Wärme-Bilanz aufgestellt, die auch die Verdunstung und die Erwärmung von Boden und Atmosphäre berücksichtigt.

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Résumé On a mesuré l'évaporation sur une surface recouverte de trèfle court à l'aide d'évapotranspiromètres (4 m²) et d'évaporimètres ouverts (12 m²) et protégés (1/3 m²); les résultats de mesures, furent comparés entre eux et avec la théorie dePenman etThornthwaite.Puis on a dressé un bilan radiatif tenant compte, de l'évaporation et du réchauffement du sol et de l'atmosphère.

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With 8 Figures