40 Reviews — Geological Survey of Great Britain. 



basin. The smaller watercourses coming from the marginal hills 

 blended their schotter with the fresh-water limestone, and the 

 transition to the present time is so gradual that the dividing-line 

 cannot be recognized. While in the more central part of the basin 

 immense masses of sediment have been deposited, those of the margin 

 are very much thinner. Erosion alone can have created the present 

 geological conformation. 



This little work is well illustrated by means of natural sections, 

 reproduced from photographs, and by numerous diagrammatic sections 

 in the text. There are also many tables of characteristic fossils. 



A. H. r. 



V. — Summary of Peogress of the Geological Survey of Great 

 Britain and the Museum of Practical Geology for 1906. 8vo; 

 pp. 181, with three text-illustrations and one plate. London, 

 1907. Price Is. 



I^HIS number of the " Summary of Progress," which was issued in 

 the autumn, is less in bulk than its predecessor by more than 

 twenty pages : a reduction due not to the fact that the publication 

 is for the first time notified as "of Great Britain," instead "of the 

 United Kingdom," but to the shorter record of field-work in Scotland. 

 Progress has been made with the mapping of the Highland Schists, 

 but at present " the difficulties of interpretation and correlation appear 

 to increase rather than diminish," and " no general theory as to the 

 structure or sequence of rocks has been formed on which all officers 

 are agreed." The rocks of the Lizard area have been undergoing 

 detailed examination, and they too have presented problems not 5'et 

 solved, as their relations with the Devonian and earlier sedimentary 

 strata on the north have yet to be demonstrated. Elsewhere in 

 Cornwall, as also in the coal-fields of South Wales, Derbyshire, and 

 Scotland, and in the adjacent tracts of older and newer strata, the 

 work has proceeded in areas often of much difficulty, but without 

 those conflicting opinions which beset the ciystalline schists. The 

 zonal distribution of fossils has received special attention in the 

 Ordovician, Silurian, and Carboniferous rocks of Pembrokeshire, and 

 in the Carboniferous of Scotland, and has not been neglected in 

 other regions. Economic geology rightly occupies some space — in the 

 details of coal-bearing strata in England, Wales, and Scotland, in 

 remarks on the eastern extension of the Nottinghamshire coal-field, in 

 the account of the fluor-spar of Derbyshire, and in the suggestion 

 made that bordering Cornwall " There must be a large amount of 

 detrital tin-ore at the bottom of certain of the bays margined by rich 

 tin-lodes." 



In the Appendix there is an essay on "The Scapolite-bearing 

 Rocks of Scotland," by Dr. J. S. Flett ; a statement of the "Total 

 quantity of Tin, Copper, and other Minerals produced in Cornwall, 

 particularly with regard to the Quantities raised from each Parish," 

 by D. A. MacAlister ; and detailed records of " Some Well-sections in 

 Middlesex," by W, Whitaker and George Barrow. 



