Notices of Memoirs — J. Oeikie. 485 



they remark, tlie weathering seems to be much more rapid than else- 

 where. They mention that on the granite near Oughterard the de- 

 cay, since the Grlacial period, appears to he from half to one and 

 a half inch, judging from the height the unweathered veins, traversing 

 the granite, stand up above the mass of the rock. 



The authors give an account of the Mines, more particularly those 

 of Glan, Oughterard, and Glengowla ; they also mention the ores 

 obtained from them. 



The "Explanation" is illustrated with several woodcuts, and it 

 has moreover the advantage of a good index. 



II. — The Cabbonifebous Fokmation of Scotland. 



AT the Meeting of the North of England Institute of Mining and 

 Mechanical Engineers, held at Glasgow, and extending over 

 four days, August 9 to 12, Mr. James Geikie, District Surveyor of 

 the Geological Survey of Scotland, read a paper on the Geology of 

 the Carboniferous formation of Scotland. The author described, 

 first, the Calciferous Sandstone series, which, when typically de- 

 veloped, consists of two groups of strata, the lower pointing to the 

 prevalence of marine conditions during the deposition of the Eed 

 Sandstones and conglomerates, and the upper showing that, during 

 its accumulation, marine and brackish water conditions alternated 

 with the occasional appearance of land surfaces. Volcanos were 

 somewhat prevalent during the deposition of both groups. Secondly, 

 he noticed the Carboniferous Limestone series, consisting of a lower 

 group indicating marine conditions and occasional old land surfaces ; 

 a middle group indicating frequent land surfaces, and alternate 

 brackish water and marine conditions ; and an upper group pointing 

 chiefly to marine conditions, with occasional brackish water-deposits 

 and a few old land surfaces. Both submarine and subaerial volca- 

 nos were active during the deposition of this series. Thirdly, he 

 drew attention to the Millstone Grit, which was deposited under 

 almost exclusively marine conditions. Fourthly, he described the 

 Coal-measures, which show a prevalence of brackish or freshwater 

 conditions, with abundant land-surfaces, and with evidence also of 

 occasional inroads of the sea. Mr. Geikie then pointed out that there 

 were intrusive rooks of three classes, namely, some referable to the 

 close of the Coal-measures ; bosses or pipes of tuff or agglomerate, 

 probably of Permian age ; and dykes of Dolerite of Miocene Age. 

 Two systems of faults of different ages were indicated, the older 

 striking north-east and south-west, the other a double-set, striking 

 approximately east and west, and north and south. In conclusion 

 Mr. Geikie referred to the exceeding richness of the variety shown 

 by the phenomena of the Scottish Carboniferous formation, and said 

 he had no hesitation in affirming that, when the palaeontological and 

 geological histories of these rocks was thoroughly worked out there 

 would be prepared one of the most important chapters in the physical 

 history of the country. — Nature, 25th August, 1870. 



