322 Revieivs — Prof. A. Geikie's Geological Sketches. 



Series (though I dissent from his views as to the origin of their 

 colour). The Avicula contorta Zone (='Ehat') Credner describes 

 as " a series of strata with prevailing clear finely-grained sandstones, 

 which are covered with grey sandy shales, and enclose the remains 

 of numerous vascular cryptogams and about 20 gymnosperms. 

 They are found especially in the Eheetics near Bayreuth and near 

 Culmbach, where they even form feeble seams of coal. . . . This 

 Ehsetic flora is certainly nearly related to that of the Upper Keuper ; 

 still the most important and characteristic species occur first in the 

 Ehgetic itself and pass up partly into the Jurassic System. The 

 Ehajtic is therefore linked to the Lias, or is a passage-formation 

 (' Zwischenbildung ') between this formation and the Keuper." 



DB :E "V IIB "W S. 



I. — Geological Sketches at Home and Abroad. By Archibald 

 Geikie, LL.D., F.E.S., Director-General of the Geological Surveys 

 of the United Kingdom. Eoyal 8vo. pp. 3S2, with 29 Illustra- 

 tions. (London : Macmillan & Co., 1882.) 

 THE Essays here collected and revised have, says Professor A. 

 Geikie, appeared at intervals in various journals, most of the 

 papers being records of geological rambles, the author has introduced 

 into them a few illustrative sketches from his note-books. Those 

 who are already acquainted with Professor Geikie's many pleasant 

 books on Geology and the Physical features of the Earth's surface, 

 may anticipate not unnaturally to find the present volume sustain 

 the high character of the author's other writings, and in this they 

 will not be disappointed. We have here brought together, in a most 

 agreeable form, graphic sketches with pen and pencil of many 

 a beautiful spot in the Highlands and Orkneys; in Norway and 

 Sweden ; among the volcanos of Central France ; in Wyoming ; 

 among the Geysers of the Yellowstone ; a chapter on Geographical 

 Evolution ; and lastly an Essay on the Geological Influences which 

 have affected the course of British History. From this last chapter 

 we venture to quote briefly. " It is obvious that no event in the 

 geological history of Britain can have had a more powerful influence 

 on its human history than the separation of this country as a group 

 of islands cut off" by a considerable channel from direct communica- 

 tion with the mainland of Europe. Let us consider for a moment 

 how the disconnection was probably brought about. 



" There can be no doubt that at the time when Britain became an 

 island, the general contour of the country was, on the whole, what 

 it is still. The same groups of mountains rose above the same 

 plains and valleys, which were traversed by the same winding 

 rivers. We know that in the glacial and later periods considerable 

 oscillations of level took place ; for, on the one hand, beds of sea- 

 shells are found at heights of 1200 or 1300 feet above the present 

 sea-level; and on the other hand, ancient forest-covered soils are 

 now seen below tide-mark. It was doubtless mainly subsidence 



