Observatory Hill Research Articles

Eclipse of radio emission on 7 March, 1970 at 10 cm wavelength from the active region associated with McMath plage 10 618

Radio emission of 10 cm from the whole disk was monitored during the eclipse of 7 March, 1970 by the Aerospace San Fernando Observatory and AFCRL Sagamore Hill Solar Radio Observatory. For both, the active region associated with sunspot 17 774, McMath region 10 618, was occulted. At Sagamore Hill the entire region was occulted. At SFO only the southern half of the sunspot group and the hydrogen plage southeast of the group was occulted. This region produced an importance class 1N flare and 10 cm burst beginning at 1601 UT and was enhanced about 15 flux units above the mean value of 190 units at onset. The Sagamore Hill data indicate the region was about 3.8′ and contributed about 0.21 of the total radiation from the disk. The SFO data gave about 5.4′ for the size of the southern half of the region and showed that about 0.20 of the total radiation came from there. Radiation came primarily from the hydrogen plage southeast of the major spot of the group. The hydrogen plage northwest of the group did not contribute significantly. Although the small flare occurred in this region, it did not contribute more than 0.04 of the total (0.20 of the active region) at occultation of region 10 618.

The Rocks

The Rocks is the historic neighbourhood on the western side of Sydney Cove. It rises steeply behind George Street and the shores of west Circular Quay to the heights of Observatory Hill. It was named The Rocks by convicts who made homes there from 1788, but has a much older name, Tallawoladah, given by the first owners of this country, the Cadigal people. Tallawoladah, the rocky headland of Warrane (Sydney Cove), had massive outcrops of rugged sandstone, and was covered with dry sclerophyll forest of pink-trunked angophora, blackbutt, red bloodwood and Sydney peppermint. The Cadigal probably burnt the bushland here to keep the country open. Archaeological evidence shows that they lit cooking fires high on the slopes, and shared meals of barbecued fish and shellfish. Perhaps they used the highest places for ceremonies and rituals. Down below, Cadigal women fished the waters of Warrane in bark canoes.

The Observatory Hill Railway of Allegheny City, Penn.

The Observatory Hill Railway of Allegheny City, Penn.

On the S. W. Extension of the Clifton Fault

On the right bank of the Avon, somewhat below the Suspension Bridge and a little beyond the Clifton station of the Bristol Port railway, the Clifton fault cuts across the strata somewhat obliquely. On the southern side of the fault is massive Mountain Limestone, forming the bold bluff of the Observatory Hill. On the northern side are much contorted red grit and limestone shales (see Map, p. 147). Viewed from the opposite side of the river, the right bank, from the Suspension Bridge for half a mile northwards, shows the following features. The eastern tower of the Suspension Bridge is built on a solid mass of limestone, the western face of which fronts the river as an almost perpendicular wall of rock. At right angles to this, and parallel with the bridge-road, there is a second face due probably to a joint plane, or a minor dislocation of the strata parallel with that caused by the Clifton fault. This vertical face forms the southern boundary of a little recess in the rocks, in which lies the Clifton station. On the northern side of the station rises the somewhat dislocated mass of limestone which forms Observatory Hill, and which, on its southern side, abuts against Millstone Grit and Upper Limestone Shales brought down by the Clifton fault. The whole appearance of the side of the ravine now changes, and in place of vertical limestone cliffs there is a wooded slope. Close to the river, however, the rocks are well seen in