86 Revieas — Dana's Ajypendix — The S. Wales Coalfield. 



abroad, more especially in America. Among the many good points 

 which we have noticed, we may more particularly mention the lucid 

 descriptions of the methods of crystal drawing and the numerous 

 worked problems illustrating in detail the methods practically 

 adopted in the calculation of the forms of crystals from the 

 measured angles. The methods of projection and the uses of 

 anharmonic ratios are also well explained. In the treatment of the 

 subject great stress is laid on the independence of the thirty-two 

 types of crystalline symmetry, and their deduction and characteristics 

 are illustrated in full detail. Most of the figures have been 

 specially drawn, and there are frequent references to the specimens 

 preserved in the Cambridge Collection. The Cambridge University 

 Press is to be heartily congratulated on this particularly handsome 

 and valuable addition to its series of Natural Science Manuals. 



M. F. 



VII. — First Appendix to the Sixth Edition of Dana's System 

 OF Mineralogy. By Edward S. Dana. pp. 75. (New- 

 York, 1899.) 



THE usefulness of the well-known Dana's System of Mineralogy, 

 the sixth edition of which was published in 1892, has been 

 increased by the issue of a First Appendix, which includes within 

 a brief compass a description of the more salient characters of the 

 new mineral species discovered during the last seven years, and 

 an account of the results of later research on the species already 

 described in the Sixth Edition itself. For convenience the mineral 

 species are noted in alphabetical order, and full references are given 

 to the original memoirs. The Appendix is brought well up to date, 

 and takes account of researches published very shortly before its 

 own appearance. M. F. 



VIII. — The Geology of the South Wales Coalfield. Part I : 

 The Country around Newport, Monmouthshire. By Aubrey 

 Strahan, M.A., F.G.S. Memoirs of the Geological Survey. 

 pp. vi, 97. (London : printed for H.M. Stationery Office, 

 1899. Price 2s.) 



THE resurvey of the great Coalfield of South Wales was com- 

 menced in 1891 by Mr. Strahan, and has been carried on with 

 the aid of Mr. J. E. Dakyns (who has now retired from the service), 

 Mr. E. H. Tiddeman, Mr. Walcot Gibson, and Mr. T. C Cantrill. 

 The present Memoir is the first of a series intended to explain the 

 one-inch geological maps of the district, of which four have now 

 been published. In it we have descriptions of the Silurian rocks of 

 Usk, of the Old Eed Sandstone, Carboniferous rocks, Keuper Marl, 

 Eh^tic Beds, Lower Lias, Glacial Drifts, and more recent deposits. 

 The Silurian rocks comprise Wenlock and Ludlow Beds, and while 

 they are overlain with apparent conformity by the Old Eed Sand- 

 stone, it is noted that the plane of demarcation is sharp and that 

 there is no evidence of gradation. This is not as we have usually 

 been taught to believe. Moreover, instead of any break in the Old 

 Eed Sandstone, marking a division into Upper and Lower beds, it is 



