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Visit to the imperial institute
VISIT TO THE IMPERIAL INSTITUTK two pebble bands. There was not time to collect fossils, but a good specimen of Panopaa t"ntermedza was found. Two feet below the upper pebble-band a 6-in. hard, calcareous, concretionary band containing fossils was traced for several yards. Above the band of pebbles was about 3 ft. of brown loam, with scattered fossils in the lower part. Mr. Whitaker suggested that 2 ft. of this loam should be included in the basementbed, which would then be 9 or 10 ft. thick. Near Little Oxhey Lane Bridge, on its northern side, the loam just described passes up into 3 or 4 ft. of sandy clay, with patches of sand, but without fossils; and above this, close up to the bridge, was seen 4 01 5 ft- of decomposed pale grey and brown clay. At the bridge there were traces of characteristic brown London Clay at the surface, but it may have been disturbed. The complete opening up of these beds makes possible a slight correction of the Geological Survey Map (Drift), Sheet 1. On the map, the line of outcrop of the Reading Beds is shown as being less than a furlong (-lo of a mile), north of Little Oxhey Lane Bridge. Observations made during the Excursions, confirmed by other examinations made by Mr. Woodhead and the writer, show that the outcrop of the Reading Beds is rather more than a furlong (ir of a mile) farther north, or about a quarter of a mile north of the bridge. On the west side of the line, opposite Sandpit Wood, there is a small plantation, shown on the Geological Survey map. The line of outcrop of the ~eading Beds will be approximately indicated by a line drawn from the south-eastern corner of the plantation, across the railway, to the middle part of Sandpit Wood, where it broadens out eastward. On both Excursions tea was taken at the Railway Hotel, Woodridings, Pinner. On September 24th, a vote of thanks was passed to the Directors, on the proposal of Mr. Whitaker, seconded by Mr. Chas. Oldham, Hon. Sec. of the Hertfordshire Natural History Society; and on November 5th Mr. Whitaker expressed the thanks of the party to the Directors. VISIT TO THE IMPERIAL INSTITUTE, SATURDAY, JANUARY 28TH, 1911. by J. W. EVANS, D.Sc., LL.B., F.G.S.)
(R~port
THE ROCKS AND MINERALS OF NATAL AND ZULULAND. THE party, which numbered about twenty-five, was conducted by Dr. Evans to the Natal Court, where Dr. Hatch, who gave a lecture to the Association on the Geology of Natal on the 2nd of December last, has arranged an important collection of rocks and minerals from that province. The formations which are known to exist in Natal are shown
VISIT TO THE IMPERIAL INSTITUTE.
157
in the accompanying stratigraphical table, which has been approved by Dr. Hatch. It is only necessary to add here that while the rocks of the Swaziland (pronounced Swawziland) system are strongly folded, those of later age are as a rule nearly horizontal, though they have been subjected to considerable faulting, which has brought them down to a much lower level on the sea-coast than in the east of the province. Attention was first directed to the metamorphic rocks, which have been included in the Swaziland system. Some are evidently of sedimentary origin. Such are the conglomerates, quartzites, quartz schists, and mica schists of the Buffalo River and the Insuzi valley, Zululand, and the Denny Dalton Mine, and the neighbourhood of Nondweni, Vryheid District. The conglomerate from the last-mentioned locality shows marked resemblance to the ancient pne-Cambrian "tillites" (consolidated boulder clays) found in different parts of the world, and may perhaps be correlated with the Lower Huronian glacial beds of Canada described by Coleman. Specimens of sheared lava flows are also shown. Of especial interest is the contorted ironstone or "calico" rock of the Umbizwa River, Zululand, and the Vryheid District, which may be paralleled with similar rocks in the Witwatersrand and Swaziland systems of the Transvaal, the Dharwar rocks of the Kolar Gold Field in India, and the Lake Superior Iron Ores. The corrugations of the ferruginous layers, which are not shared by the arenaceous rocks above and below, can only be explained by expansion due to chemical change before they were covered up by any considerable thickness of deposits. The conversion of hrematite into chalybite, for instance, would cause an increase in volume of nearly one hundred per cent. The crystalline dolomitic limestone from Port Shepstonc, and the metamorphic minerals it contains, recently described by Dr. Hatch (Q. .f. G. S., vol. lxvi, 1910, p. 507), were also noticed, as were the chlorite and hornblende schists which no doubt represent altered igneous rocks. The rocks intrusive in the Swaziland system are well represented. Hornblende schists are" injected" with acid rocks at Mvuzana Spruit, near Fort Yolland, and intrusions of granite, syenite, and quartz felspar rocks occur on a large scale in the Vryheid District and Zululand. In the former there are also intrusions of dolerite showing xenocrysts of felspar and xenoliths of granite. Serpentine formed by the hydration of peridotite is met with near Fort Yolland, and contains veins of serpentine asbestos, the karystiolite of the ancients, while chromite is found in the serpentine of Tugela Rand, Krantzkop. Samples are also exhibited of auriferous quartz, galena, and copper ore, including native copper in joint.5 in syenite.
158
VISIT TO THE MARBLE WORKS, HAYES, MIDDLESEX.
The lithological characters of the Table Mountain Sandstone and Karroo system are illustrated by typical specimens which include the Dwyka glacial conglomerate or tillite, its scratched boulders, and the striated floor on which it rests. The chief economic product of the Karroo beds is the coal, of which specimens are shown in the court. They also contain, near Prestwick and De Jager's Drift, valuable beds of iron ore, and, near Weenen, beds and nodules of phosphatic material formed from the remains of fish, the scales of which are shown. A sample of fossil wood from the same formation near Ladysmith is also exhibited. Near Doornkloof intrusive dolerites have in some places metamorphosed the coal into graphite, which, though no doubt available for use in pencils, is of little use for the manufacture of crucibles. For this purpose the flake graphite found in crystalline dolomitic limestone near Port Shepstone and in gneiss at N'changa is more useful, though the cost of separation from the other minerals of the rock is of course considerable. Samples are exhibited of the iron and manganese ores and limestone occurring as surface formations.
VISIT TO THE MARBLE WORKS OF ARTHUR LEE & BROS., LTD., HAYES, MIDDLESEX. SATURDAY, FEBRUARY IITH, 1911.
Excursion Secretary: A. C. (Report by W. G.
YOUNG.
RENWICK.)
THE party, numbering about 35, left Paddington by the 2.5 p.m. train, arriving at the works at 2.45. Here they were received by the General Manager, Mr. H. C. Tanner, and Mr. W. G. Renwick, and conducted through the works. The stock comprises over eighty varieties of marbles, ranging in time from Lower Silurian (Honister Green) to Upper Miocene, in which (.ccur the Travertines or Onyx Marbles. Particular attention was directed to the stacks (nearly 200 tons) of very beautiful Onyx Marble (Travertine) from Arizona, U.S.A. Specimen pieces cut parallel to and across the bedding planes were exhibited, and the blocks sprayed with water, when the admirable colour effects, only brought out in full by polishing, were readily discernible. Among many others the following were of especial interest: Saint Katherine, a spar marble of Triassic age, obtained from the Spanish Pyrenees, interesting on account of its peculiar crys-
(R~port
THE ROCKS AND MINERALS OF NATAL AND ZULULAND. THE party, which numbered about twenty-five, was conducted by Dr. Evans to the Natal Court, where Dr. Hatch, who gave a lecture to the Association on the Geology of Natal on the 2nd of December last, has arranged an important collection of rocks and minerals from that province. The formations which are known to exist in Natal are shown
VISIT TO THE IMPERIAL INSTITUTE.
157
in the accompanying stratigraphical table, which has been approved by Dr. Hatch. It is only necessary to add here that while the rocks of the Swaziland (pronounced Swawziland) system are strongly folded, those of later age are as a rule nearly horizontal, though they have been subjected to considerable faulting, which has brought them down to a much lower level on the sea-coast than in the east of the province. Attention was first directed to the metamorphic rocks, which have been included in the Swaziland system. Some are evidently of sedimentary origin. Such are the conglomerates, quartzites, quartz schists, and mica schists of the Buffalo River and the Insuzi valley, Zululand, and the Denny Dalton Mine, and the neighbourhood of Nondweni, Vryheid District. The conglomerate from the last-mentioned locality shows marked resemblance to the ancient pne-Cambrian "tillites" (consolidated boulder clays) found in different parts of the world, and may perhaps be correlated with the Lower Huronian glacial beds of Canada described by Coleman. Specimens of sheared lava flows are also shown. Of especial interest is the contorted ironstone or "calico" rock of the Umbizwa River, Zululand, and the Vryheid District, which may be paralleled with similar rocks in the Witwatersrand and Swaziland systems of the Transvaal, the Dharwar rocks of the Kolar Gold Field in India, and the Lake Superior Iron Ores. The corrugations of the ferruginous layers, which are not shared by the arenaceous rocks above and below, can only be explained by expansion due to chemical change before they were covered up by any considerable thickness of deposits. The conversion of hrematite into chalybite, for instance, would cause an increase in volume of nearly one hundred per cent. The crystalline dolomitic limestone from Port Shepstonc, and the metamorphic minerals it contains, recently described by Dr. Hatch (Q. .f. G. S., vol. lxvi, 1910, p. 507), were also noticed, as were the chlorite and hornblende schists which no doubt represent altered igneous rocks. The rocks intrusive in the Swaziland system are well represented. Hornblende schists are" injected" with acid rocks at Mvuzana Spruit, near Fort Yolland, and intrusions of granite, syenite, and quartz felspar rocks occur on a large scale in the Vryheid District and Zululand. In the former there are also intrusions of dolerite showing xenocrysts of felspar and xenoliths of granite. Serpentine formed by the hydration of peridotite is met with near Fort Yolland, and contains veins of serpentine asbestos, the karystiolite of the ancients, while chromite is found in the serpentine of Tugela Rand, Krantzkop. Samples are also exhibited of auriferous quartz, galena, and copper ore, including native copper in joint.5 in syenite.
158
VISIT TO THE MARBLE WORKS, HAYES, MIDDLESEX.
The lithological characters of the Table Mountain Sandstone and Karroo system are illustrated by typical specimens which include the Dwyka glacial conglomerate or tillite, its scratched boulders, and the striated floor on which it rests. The chief economic product of the Karroo beds is the coal, of which specimens are shown in the court. They also contain, near Prestwick and De Jager's Drift, valuable beds of iron ore, and, near Weenen, beds and nodules of phosphatic material formed from the remains of fish, the scales of which are shown. A sample of fossil wood from the same formation near Ladysmith is also exhibited. Near Doornkloof intrusive dolerites have in some places metamorphosed the coal into graphite, which, though no doubt available for use in pencils, is of little use for the manufacture of crucibles. For this purpose the flake graphite found in crystalline dolomitic limestone near Port Shepstone and in gneiss at N'changa is more useful, though the cost of separation from the other minerals of the rock is of course considerable. Samples are exhibited of the iron and manganese ores and limestone occurring as surface formations.
VISIT TO THE MARBLE WORKS OF ARTHUR LEE & BROS., LTD., HAYES, MIDDLESEX. SATURDAY, FEBRUARY IITH, 1911.
Excursion Secretary: A. C. (Report by W. G.
YOUNG.
RENWICK.)
THE party, numbering about 35, left Paddington by the 2.5 p.m. train, arriving at the works at 2.45. Here they were received by the General Manager, Mr. H. C. Tanner, and Mr. W. G. Renwick, and conducted through the works. The stock comprises over eighty varieties of marbles, ranging in time from Lower Silurian (Honister Green) to Upper Miocene, in which (.ccur the Travertines or Onyx Marbles. Particular attention was directed to the stacks (nearly 200 tons) of very beautiful Onyx Marble (Travertine) from Arizona, U.S.A. Specimen pieces cut parallel to and across the bedding planes were exhibited, and the blocks sprayed with water, when the admirable colour effects, only brought out in full by polishing, were readily discernible. Among many others the following were of especial interest: Saint Katherine, a spar marble of Triassic age, obtained from the Spanish Pyrenees, interesting on account of its peculiar crys-