426 Revieus — Transvaal Geology. 



have been intruded a vast series of sills or dykes of diabase or altered 

 dolerite. The author regards it as inconceivable that such an immense 

 mass of igneous rock should flow over and rest upon the ferruginous 

 and calcareous rocks without absorbing luaterial from them. The 

 Karroo laccolite, formed of dolerite, occupies an area about 700 miles 

 long by 200 broad, while the individual sills are from 100 to 500 

 feet thick ; and Professor Schwarz estimates that the entire material 

 would, if melted up, form a ball 50 miles in diameter. He has no 

 doubt that a considerable amount of sedimentary material has been 

 assimilated. Thus a dyke 100 feet or more thick may have been 

 intruded at a high angle and then bend over to follow the bedding 

 plane of the sediments as a sill. If the dolerite were entirely new 

 material, that had not melted out its cavitj', there should be visible 

 above the bend of the dyke to the sill some continuance of the crack 

 through which the dolerite came, but he has seen no evidence of this 

 in the Karroo. 



VI. — Geological Sukvez of the Tkansvaal. — Memoir Xo. 6, issued 

 by the Mines Department, Pretoria, 1912, is entitled Hie Geology of 

 the Murchison Range and District; it is by Mr. A. L. Hall, B.A., 

 E.G.S., and is accompanied by a geological map on the scale of about 

 1 inch to 2\ miles. The Murchison Range, which attains an elevation 

 of 2,980 feet, is formed mainly of the Moodies' Series, consisting of 

 quartzites, phyllites, slates, and conglomerates, with ironstones and 

 limestones ; and this series presents characters that suggest correlation 

 with the Swaziland system. The Black Iteef and succeeding Dolomite 

 Series of the Transvaal system, rest unconformablj' on the Moodies' 

 Series. The granite of the Low Country is intrusive into the older 

 rocks of the Murchison range, and occupies as regards age a position 

 between those rocks and the Transvaal system. Economically the 

 lUack Reef Series and the older Schist belts of the Murchison range 

 are of importance as gold-beai'ing rocks; there are likewise extensive 

 tracts of mica, some of which occur in coarse white granite pegmatites 

 that are intrusive into the older granite, while others are associated 

 with the newer Palabora granite. Deposits of corundum also occur, 

 but at present it is not possible to estimate the quantity available. 

 More prospecting is required in reference to all the mineral deposits, 

 but the author regards the district as specially suited for small mining 

 enterprises. He further observes that there are remarkably fertile 

 stretches of countrj' with permanent and abundant water and a healthy 

 climate, admirably adapted for agricultural operations. 



YII. — Geological Survey of New Zealand. — A quarto volume on 

 The Geology of the Bun Mountain Subdivison Nelson, by Messrs. J. M. 

 liell, E. de C. Clarke, and P. Marshall, forms the subject of an 

 official Bulletin (No. 12, New Series, Wellington, 1911). The area 

 liere described lies in the northern part of the southern island of 

 New Zealand, bordering Tasman Bay. The eastern portion, occupied 

 by forest-covered mountains, rises to more than 3,000 feet above sea- 

 level ; the western part, drained by the River Waimea and its 



