principally within the Tertiary era, and mainly within the latter half of it. In fact, none of the mountains which bound the Indian Empire appear to have existed in anything like their present form or size at the commencement of the Tertiary era. The Indo-Gangetic alluvium occupies a zone of depression formed entirely within the Tertiary era concomitantly with the elevation of the extra-Peninsular ranges. The surface deposits are all Recent or Pleistocene in age, but the occurrence of extinct mammals in the alluvium of the Jumna, some of which are identical with those of the uppermost Siwalik beds, points to an Upper Tertiary age of the deeper seated deposits of the Gangetic alluvium, whose thickness has been proved to reach 1,300 feet under Lucknow. The Peninsular area differs from the extra-Peninsular in having been dry land since the close of the Palæozoic era, and in the very small amount of disturbance the rocks have undergone during this period. Two of its main geographical features appear to be of very ancient date. On the north-west the Aravalli range of the present day is the mere wreck of a mountain range whose elevation was completed in the Vindhyan period; the exact age of this system cannot be determined, as no fossils have been found in it, but it is certainly pre-Carboniferous, though probably not much older than Devonian. On the east the present coastline appears to have been approximately determined about the same period, and the manner in which the small patches of marine deposits found on the east coast thin out against the older rocks shows that throughout the Secondary era the sea could never have extended much west of the present coast, though dry land may at times have extended further to the east. The west coast appears to be of much more recent origin. Throughout the Secondary era there seems to have been a more or less continuous land connection between Southern India and South Africa; at the close of the Secondary era, however, this was broken up, the present west coast defined, and the range of the Western Ghats elevated. The paleontological evidence of the former connection between India and Africa is very complete, and, besides this, there is a very remarkable analogy between the geology of the two regions. The Karoo series of the interior of South Africa and the Uitenhage series of the coast are represented in India physically, stratigraphically, and paleontologically by the Gondwanas of the interior of the Peninsula and the Upper Gondwana outliers of the east coast. So far reference has only been made to the most important features of what is known, and it will be well now to point out briefly what has still to be done. Within the thoroughly settled districts of the Peninsula large areas have been left uncoloured because absolutely nothing is known of them, and even in the area which has been coloured much remains to be done. The vast area coloured with one uniform tint of pink contains many varieties of rock, and at least two-probably many more successive systems of deposits, besides intrusive and eruptive rocks of the most diverse kinds. The succession and correlation of the various rock systems which are classed as Transition, Cuddapah, and Vindhyan have yet to be established; while the relation between the Upper and Lower Gondwana beds and the proper classification of this great series of river deposits, ranging in age from Carboniferous to Cretaceous, have still to be worked out. In the extra-Peninsular area the Himalayas have much information to yield, especially as regards the zonal distribution of the Siwalik fauna, and the sequence and correlation of the great series of as yet unfossiliferous slates and limestones of the North-west Himalayas. On the east our newly-acquired province of Burma, besides almost the whole of Assam, has to be surveyed, and the very fine series of Tertiary rocks and the economically important mineral deposits have to be examined in detail. If fact, the most pressing need of the immediate future is not so much the exploration and imperfect examination of new regions as the completion and Elling up of gaps in our knowledge of the geology of the land which lies within our frontier. 8. Geological Sketch of Central East Africa. By WALCOT GIBSON, F.G.S. The tract of country described in this paper is situated in Equatorial East Africa. It extends from the coast inland to the N.W. borders of Victoria Nyanza. The small island of Mombasa, the starting-point of the expedition, lies fifty miles north of the island of Pemba. A narrow creek, fordable at low water, separates the island from the mainland. The sea cliffs are composed of coral rock, which also forms an inland belt about two miles broad, with a general elevation of 50 feet, which sometimes rises to 100 feet. A fringing reef borders the coast. The shore sand consists of comminuted corals and shells mixed with rounded fragments of quartz, orthoclase, garnets, and splinters of clear blue cyanite. These constituents appear to be derived from a submerged ridge, of which the Seychelles Islands are a remnant. The coral rock rests on a sedimentary series consisting of shales, limestones, flaggy sandstones, grits, and conglomerates in descending order. The beds dip gently to the east. They extend inland to the borders of the Taru Plain, a distance of about forty-seven miles. The beds are of marine origin, ammonites and ichthyosaurian remains having been found near Rabai and other localities. It is impossible to correlate these beds with any occurring in South Africa, but they appear to form a belt running many miles north and south of Mombasa. The sedimentary beds rest unconformably on a metamorphic series, consisting of gneisses, schists, and intrusive granites. The strike is N.N.W. and S.S.E., and the dip is generally high. The beds are often intensely folded (Ndange River). Biotite is the commonest mica, and orthoclase the predominant felspar. The schists contain much cyanite, full of iron inclusions. Common garnets are plentiful. Hornblendic rocks are remarkably scarce, the main mass being micaceous. Graphite schists occur, and the Bura Hills are largely composed of a crystalline limestone containing scales of graphite. No fossils could be detected. Quartz veins and quartzites are only feebly developed. They form gently undulating country or else nearly level plains (Taru, Serengeti) through which low isolated hills of gneiss and granite protrude. It is evident that they have suffered enormous denudation. They no doubt represent a complex metamorphosed series of sediments and intrusive rocks, but of what geological age or ages it is impossible to state. The intrusive granites are generally pegmatites. Porphyritic granite covers a large area in Kavirondo. Biotite is the essential mica, and a pink orthoclase the predominant felspar. The relation of this large mass of granite to the gneisses and schists could not be ascertained. The area covered by granite and metamorphic rocks is enormous. Fully twothirds of Central East Africa are composed of these rocks. The remaining portion of the country, excepting the narrow coast belt of sedimentary rocks, is formed of recent volcanic rocks. No traces of the fossiliferous sandstones and shales found by Professor Drummond near Lake Tanganyika, and quite recently by Mr. Joseph Thomson to the west of Lake Nyassa and around Lake Bangweolo, were detected. If further investigation proves their absence from East Africa to be a fact, then we have in the deposits around Lake Tanganyika the most northerly extension of the Karoo beds of South Africa. Volcanic rocks form the grandest scenery in East Africa. They occur in two forms, giving rise to two distinct types of scenery. They have either built up tall isolated mountains like Kilimanjaro (19,718 ft.), Kenia (18,000 ft.), Elgon (14,000 ft.), Chibchangani (12,000 ft.), besides numerous other smaller hills, or they are arranged in lines running north and south. The lavas, tuffs, and ashes composing the high central plateaux of Mau, Kamasia, and Lykipia have evidently issued from a north and south fissure. The site of this fissure is now occupied by the chain of lakes commencing with Naivasha on the south, and terminating northward in Lake Baringo. Along this line recent eruptions, some still giving out steam, have broken out, and it is the interception of the drainage by the material thrown out from these vents that forms the lakes Naivasha, Nakuru, and Elmeteita. Highly acid and ultra-basic rocks are represented. Kilimanjaro and the Kyulu Mountains are chiefly built up of basic rocks, while the lavas of Lykipia and the Mau plateaux are chiefly acid. It appears that the latter localities have been the seat from which acid lavas have continued to be poured from times prior to the first eruptions of Kilimanjaro up to the present day. The basic lavas of Kilimanjaro do not extend very far from the original point of issue. At least this is so to the north, for no lavas were found on the plains of Lytokitok, distant thirty miles north of Kilimanjaro. On the other hand the acid lavas of Mau and Lykipia extend for great distances. Eastwards they stretch as far as the Athé plain, about fifty miles, and westwards to near the shores of Victoria Nyanza, a distance of nearly one hundred miles. Further westward, in Busoga and Buganda, basic igneous rocks pierce the metamorphic rocks, but without possessing any general trend. With the exception of the still active volcanoes it is impossible to state even the approximate geological age of any of the eruptions. Some of the volcanoes are possibly only dormant, others are certainly extinct, but none appears to be of great geological antiquity. All that can be safely asserted is that they are long subsequent to the deposition of strata containing ammonites, for, whereas the conglomerates of these sedimentary deposits contain pebbles of schist and gneiss, they nowhere yield fragments of igneous or volcanic rocks. 9. Report on the Volcanic Phenomena of Vesuvius.-See Reports, p. 471. 10. On Quartz Enclosures in Lavas of Stromboli and Strombolicchio, and their Effect on the Composition of the Rock. By Professor H. J. JOHNSTON-LAVIS, M.D., M.R.C.S., B.-ès-Sc., F.G.S. In a recent dolerite lava stream that reaches the sea at Punta Pietrazza, on the island of Stromboli, are numerous inclusions of vein quartz and quartzite. These attain several centimetres in diameter; some specimens are almost clear glassy, while others are opaque and granular. They have undergone more or less softening and fluxion, if not actual fusion, by the lava. They are surrounded by a glassy crust containing numerous augite crystals, more especially at the periphery. Where the glassy envelope has formed veins penetrating along the fissures in the quartz, augite crystals have crystallised out of this vitreous fluid. The amount of augite in the vicinity of these quartz enclosures is greater than the average in the surrounding lava, showing that the quartz has afforded a material necessary for the individualisation of augite. The crystallisation of such out of the glass envelope would have been more complete if sudden cooling of the lava had not prevented such a result. The small island of Strombolicchio, close to Stromboli, is the wreck of an old volcanic neck. The rock composing it is lighter than the lavas of Stromboli, being of a purple tint, in which dark bottle-coloured and also bright emerald green augites are visible, the latter being fewer but very striking. The Strombolicchio rock is crowded with quartz enclosures, more opaque, more granular, and enwreathed with numerous emerald green augites. This green crust is seen microscopically to be composed of mixed grains of quartz and augite. We can trace the emerald green augites to an origin in the quartz which has combined with the residual fluid of basic oxides with insufficient silica for the individualisation of a mineral to form an augite. The process is seen better here on account of the slow cooling of the plug and the absence of the mechanical disturbance in the flowing stream of lava of the Punta Pietrazza. I have elsewhere shown the olivine nodules and many loose crystals are nothing more than altered limestone enclosures, and here we see quartz adding augite to a lava which may owe its diminished acidity in part to the absorption and conversion of quartz into augite, the supply of the free silica possibly affecting the rock in other ways as to its composition, not so easily demonstrable as the one here described. This is one more fact which goes to show that igneous rocks are markedly modified in their composition by the rocks they traverse. I have pointed out elsewhere that it is not a case of simple fusion or fluxion but rather one of selective diffusion. 11. On the Gypsum Deposits of Nottinghamshire and Derbyshire. The gypsum deposits of Nottinghamshire and Derbyshire belong to the Keuper series (Triassic). The Upper Marls,' in which the gypsum deposits occur, consist of beds of marls with minor bands of sandstone. Rock salt is apparently absent in both counties, but gypsum is abundant. The chief gypsum works in Nottinghamshire are at Newark, Orston, Barton, Thrumpton Gotham, and Kingston, and in Derbyshire at Chellaston and Aston. The gypsum varies in thickness from a mere film to fifteen feet or so, and occurs in the marls in the form of bowls,' 'cakes,' beds, and thin bands or veins, and in every degree of purity. The more massive portions are usually saccharoidal or amorphous, and the purest kind is by the trade termed 'Superfine.' The tough variety, commonly called Alabaster,' which is worked up into ornaments, is found only in the Chellaston district. The thin bands or 'rivings' are fibrous ('satin spar). These gypsum deposits were probably formed in salt lakes or inland seas, similar to the Dead Sea and the Great Salt Lake of Utah. After extraction gypsum is cleaned, ground down to flour, and burnt. The burning drives off the combined water. When ground down to flour and properly burnt gypsum possesses the valuable property of recombining with water, and setting from a thin paste into a solid mass. The mineral thus treated forms plaster of Paris, and is an ingredient in Keene's and other hardened cements. 12. Report on Photographs of Geological Interest.—See Reports, p. 473. 13. On a Bed of Oolitic Iron-ore in the Lias of Raasay. [Communicated by permission of the Director-General of the Geological Survey.] The author drew attention to the occurrence in Raasay of a bed of oolitic ironore which had not been previously noticed. The bed in question attains a thickness of five feet, and lies at the top of the Middle Lias, beneath the dark shales of the Upper Lias. The stratigraphical position is thus approximately the same as that of the Cleveland iron-ore, although in Yorkshire the upper part of the Middle Lias contains a series of ironstone bands. An analysis of the Raasay ore, made by Mr. A. B. Dick, showed in the grey (unweathered) rock 29 per cent., and in the brown (weathered) rock 37 per cent., of metallic iron. The discovery of the iron-ore was made during the progress of the Geological Survey. 14. Note on a Transported Mass of Chalk in the Boulder Clay at Catworth in Huntingdonshire. By A. C. G. CAMERON, Geological Survey. [Communicated by permission of the Director-General of the Survey.] In this paper the author comments upon the abundance of chalk fragments and boulders that culminate in the Drift around the highest points in the county west of the town of Huntingdon. At particular elevated spots there are outcrops of white Chalk which are dug up and used about the farmyards, where it sets hard, making a firm bottom like cement. At Catworth, near Kimbolton, on the summit. of high ground overlooking the plain of the Oxford Clay, there is a mass of chalk of great size, regularly interstratified with flint and lying on Boulder Clay. The very unusual phenomenon is presented of a village, or the greater and principal part of a village, built on chalk far away from any place where the Chalk formation occurs in place, or any outliers of that rock are seen. The evidence is striking. There are ponds and pits about in bare chalk, the soil in the gardens is chalk, and the graves in the churchyard leave off in chalk. There are numerous old excavations besides, whence hundreds of loads of chalk have been got out and carted away to the farms adjacent. The flints in this chalk are angular, and show little signs of being weathered or worn, and there are in it besides thick tabular masses of flint. Copious springs issue at the base of this chalk, and it is therefore an important water-bearing bed in the village. The water in the wells sunk through the chalk to the clay beneath frequently runs over the top; while in that portion of the village which is outside the chalk area no water can be got by sinking in the clay. Besides Chalk there are boulders of other rocks clustered about this village, but none of notable size. It is not clear whether the Catworth Chalk is all one boulder-it may, perhaps, be several boulders with clay between-but as the material has been transported unaltered from the parent rock, it is not, in any sense of the term, a reconstructed chalk. 15. Augen Structure in Relation to the Origin of Eruptive Rocks and Gneiss. By J. G. GOODCHILD, F. G.S. The author discriminates between two types of augen structure-that (also termed phacoidal structure) in which the 'eyes' are not necessarily crystalline in structure, but are the unsheared portions of the rock which have escaped conversion into the schist to which their matrix has been reduced, and that in which the 'eyes' are crystalline minerals, generally undeformed, and of later date in origin than the movements which have produced the schistosity. True augen structure occurs under two different conditions. In the one the constituents out of which the augen have been formed were already in existence within the rock, and their development in a crystalline form is merely a case of regeneration under plutonic conditions. In the other class of augen structure one or more of the essential constituents that go to form the eyes' did not originally exist within the rock, but have been introduced at a late period in its history from some foreign source. Both of these classes of augen structure appear to be due to segregatory action, which came into play at a time when the rocks in which the structure occurs were in a potentially molten condition arising from the heat developed by earth movements acting under great pressure. Under these conditions of high temperature a slight and very gradual relief of the pressure referred to permitted some of the less refractory minerals to pass into a condition which favoured their segregating from a state of diffusion throughout the mass. Under these circumstances the more refractory minerals remained practically unaffected. If, following the diminution of pressure (which is equivalent in this case to a rise of temperature), there ensued a fall of temperature, the newly-formed minerals passed into the crystalline condition, while the rock material within which the augen had been developed still retained the schistose or other structure impressed upon it by the earth movements of prior date. According to this view, therefore, phacoidal amphibolite and augen-amphibolite are respectively the results of mechanical and chemical action upon the same original type of rock. In the other types of augen structure the eyes' are developed by the heat generated by earth movements, as in the former case; but an essential component of one or more of the constituents of the augen has been derived from an outside source. Augen of this class may consist of any one of several minerals; but those of most importance in the present connection are the |