Reviews — The Micrographic Dictionary. 183 



even on tlie extreme supposition that all the so-called Devonian was 

 newer than nearly all the so-called Old Eed. 



Much valuable new matter has been introduced into the description 

 of the Lower Cretaceous rocks, and a more full discussion of the age 

 of the Blackdown Beds is given at p. 277. 



We need go no further than to notice how all the newest evidence 

 to be obtained as to the fossil flora of Miocene and other periods, and 

 the many new facts and theories bearing upon glacial phenomena, 

 have been weighed, and the results clearly stated, to show that we 

 have in the " Student's Elements" a most valuable epitome of the 

 present state of our knowledge of stratigraphical geology. 



In conclusion, we will only say that those who would learn the 

 true method of working out the great problems of Geology should 

 study that most readable and philosophic work The Principles, and 

 those who would learn what are the data upon which the story of 

 the ancient earth has been founded should avail themselves of that 

 most concise and clear summary, the Student's Elements. 



III. — The MicRoaRAPHio Dictionary : a Guide to the Examina- 

 tion AND Investigation of the Structure and Nature of 

 Microscopic Objects. By J. W. Griffith, M.D., etc., and 

 Arthur Henfrey, F.E.S., etc. Third edition, edited by Dr. 

 Griffith, assisted by the Eev. M. J. Berkeley, M.A., and 

 Professor T. Eupert Jones, F.G.S. 8vo. Van Voorst, London. 

 Parts I. to VL September, 1871, to February, 1872. 



WE must draw the attention of our readers to the "Micrographic 

 Dictionary," now in course of publication, as very useful to the 

 geologist, whether naturalist or physicist, whether paleeontologically 

 or mineralogically inclined. Besides the habitual use of the pocket- 

 glass or hand-lens, recourse must often be had now-a-days to a good 

 microscope, to determine the structure of rocks and the nature of 

 minute fossils ; and, for comparison with these, chemical products 

 and living organisms have to be microscopically studied with equal 

 care and exactness. Students and workers have an extensive choice 

 of manuals, text-books, and introductions to the use of the micro- 

 scope, and for the recognition of microscopic objects, in the numerous 

 books by Carpenter, Quekett, Griffith, Hogg, Lankester, and others. 

 These authors have classified the natural objects under examination, 

 and the first-named has given a chapter on the application of the 

 microscope to geological investigation. A very wide field, however, 

 is open for histologists in " microgeology," or "clinology," as the 

 study of rocks by means of the microscope has been termed. The 

 labours of Ehrenberg, richly illustrated in his "^ Mikrogeologie " ; 

 the enthusiastic work of Schaf hautl ; the systematic researches of 

 Delesse, Naumann, Sorby, David Forbes, and Allport; the occasional 

 contributions of De Beaumont, Bischoff, Scheerer, Brewster, Phillips, 

 Eeade, Bryson, Dawson, and others, at home and abroad, — all indicate 

 the path by which the miorogeologist is to advance towards a clearer 



