48 Reviews — The Problem of the Bray Series. 



and Derbyshire should be so poor in silver, unlike North Wales, 

 for example, and especially Devon and Cornwall. The most striking 

 development of silver-production of late years is undoubtedly the 

 Cobalt district of Ontario ; Canada now occupies the third place in 

 respect to output of all the countries of the world. 



All the usual details and tables are given, as in the other volumes 

 of this series, and the work concludes with a very complete 

 bibliography. 



The Problem of the Bray Series. By Grenville A. J. Cole, 

 F.E.S. Proc. Eoy. Irish Acad., vol. xxxvi. Section B, No. 1, 

 pp. 10. 1921. 



TN this paper the literature of the Bray Series is reviewed and the 

 -^ various theories discussed, including the work of Pro- 

 fessor Sollas. The author concludes that the present anomalous 

 position of the old rocks of Bray Head and CarrickgoUogan 

 is due to an overthrust, by which they have been carried up over 

 the Ordovician and Silurian rocks subsequently to the intrusion of 

 the Leinster granite. This is comparable to the horizontal dis- 

 placements recognized by SoUas at Howth, and to certain structures 

 described by Matley and by Greenly in Anglesey. The date of the 

 overthrust is considered to be probably late Caledonian, although 

 a,n Armorican relation is not definitely excluded. 



On. Some Mineral Occurrences in the Namib Desert. By 

 P. A. Wagner. Trans. Geol. Soc. South Africa, vol. xxiv, 

 1921, pp. 71-97, with 2 plates and 2 text-figures. 



T^HE Namib Desert region, forming part of the Soutb-West 

 Protectorate, is occupied mainly by ancient crystalline rocks 

 belonging to the Fundamental Complex of that region. Among 

 these rocks are many occurrences of considerable mineralogical and 

 petrological interest, some being fine examples of metamorphism, 

 while others are of pegmatitic origin. Among the rocks and minerals 

 here described are the itabirite deposits in the hinterland of Walvis 

 Bay, which are found to be too siliceous to be of any commercial 

 value at present ; two interesting examples of cordierite rock, one of 

 which yields fine blue crystals like the " water sapphires " of Ceylon 

 and some remarkable occurrences of garnet, beryl, rose-quartz, and 

 felspar in pegmatites. Some of the beryls are good enough for 

 gemstones, as aquamarine and heliodore, greenish-blue and golden, 

 respectively ; the last-named contains uranium. A promising 

 -deposit of phlogophite in a diopside rock, associated with forsterite 

 marble and pegmatite, is being opened up near Eossing Station. 



