AERIAL SURVEY: COLONY OF HONG KONG

This paper describes the planning and implementation of a very extensive aerial survey contract undertaken by Hunting Surveys on behalf of the Hong Kong Government. From photography carried out during January and February 1963, photogrammetric plotting at 1 : 600 and 1 : 1200 proceeded steadily over a period of 5 years to the point where all but the highest land in the Colony had been surveyed at one or other of these two large scales. The problems arising from the rather unique terrain conditions and the urban and industrial development of Hong Kong are dealt with mainly from the photographic and photogrammetric aspect but reference is made to the contribution of the Crown Lands and Survey Office of the Public Works Department of Hong Kong, who provided all ground control and undertook field verification.     

The delay between solar activity and density changes in the upper atmosphere

Since 1958 it is known that there exists a response time of the upper atmosphere to changes in solar activity. This response time is best described as the lag between the 27-day variation of solar decimeter flux and the observed density changes of the upper atmosphere. Roemer obtained as a mean observational value for this lag 1.0 ± 0.12 days. Volland's simplified version of the Harris-Priester model of the upper atmosphere is used to calculate the delay which can be expected from theory. Only the effect of solar EUV radiation is taken into account. A possible influence of the corpuscular component of the solar radiation is not included in our estimate.

The calculations are carried out for the Harris-Priester model with solar activity index and a variation of . The resulting delay is 0.6 days. The calculated amplitude of the variations of the diurnal average temperatures during the solar 27-days cycle is in very good agreement with Jacchia's empirical formula.     

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.     

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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.