Apeil 14, 1899.] 



SCIENCE. 



547 



for those of a liquid are greater than the at- 

 tractions ' p. 142 ; ' zinc has a greater af- 

 finity for oxygen than copper,' p. 386; 'the 

 bond uniting the hydrogen to the acid radi- 

 cal SOi will be ruptured,' p. 388; 'an elec- 

 trolyte capable of a reaction with one of 

 the conductors,' p. 388, should be retained 

 in a modern text-boot. Exception must be 

 taken also to the use of the word ' molecule ' 

 on p. 237 without any explanation ; to the 

 phrase ' mechanical equivalent at 15° C. ,' on p. 

 264 ; to the explanation of what is meant by a 

 ' reversible ' cycle on p. 269 ; to the definition 

 of the 'ampere ;' to the use of the expression 

 ' stationary waves ;' and to the expression ' it 

 is assumed that the current enters.' 



Certain explanations are undoubtedly erro- 

 neous, such as those of electrolysis, scintillation 

 and the theory of ' angle of contact ' in cap- 

 illarity ; while others are not rigid or not defi- 

 nite, such as those of the simple pendulum, the 

 barometer, Kontgen rays, iridescence. 



There are several slight mistakes throughout 

 the book, such as the incomplete statement of 

 Doppler's principle, the use of R instead of 

 R„ in the two formulae of Van't HofFon pages 

 236 and 240, the statement on page 263 that 

 there are discrepancies between the values of 

 the mechanical equivalent as found by the two 

 methods. 



As a text- book of the character evidently 

 planned by its authors this treatise must, how- 

 ever, be considered most successful. It is a 

 book to which every student would have occa- 

 sion to refer from time to time, and which con- 

 tains within its covers much more matter than 

 any existing book of its class. The style is 

 pleasant, attractive and definite, and every 

 laboratory and library would do well to pur- 

 chase the book. 



J. S. Ames. 



Johns Hopkins University. 



The Principles of Siratigraphical Geology. By 

 J. E. Maer. Cambridge Natural Science 

 Manuals, Geological Series. Cambridge, Uni- 

 versity Press ; New York, The Macmillan 

 , Co. 1898. Pp. 304. 

 Here is a book on a single department of 



geological science which is the type of many 



another. Written to give students some idea 

 of the methods and scope of stratigraphical 

 geology, it combines a digest of the contents of 

 larger standard manuals, with an elaboration 

 of some points according to the author's views, 

 and requires for its full understanding a famil- 

 iarity with structural and dynamical geology, 

 the nomenclature of paleontology, and a minute 

 acquaintance with the local nomenclature of 

 English geography. 



The omissions in the earlier chapters imply 

 that the student is preparing for field work 

 after having read Lyell's Principles and Geikie's 

 or some other text-book, while the substance of 

 the chapters reads like lectures given to a class 

 of beginners. 



The second half of the book is by far the 

 more valuable, in that it gives a brief, but clear 

 and well-written summary of the stratigraphy of 

 Great Britain, with here and there references 

 to the more conspicuous points of stratigraph- 

 ical classification in other countries. The 

 stratigraphy of England, Wales and Scotland is 

 described with just enough detail to bring out 

 the difTei'ences of sedimentation in separate 

 regions for each period, and shows the growth 

 of the island during geological time. 



A fuller treatment of this element of stratig- 

 raphy is given in Jukes-Brown's 'Building of 

 the British Isles.' 



Some of the author's peculiarities are seen in 

 his classification and use of terms. 



Lapworth's term Ordovician is adopted. In 

 his list of systems are included Permo-Car- 

 boniferous and Permian, in addition to the Car- 

 boniferous. 



The grounds of this usage are 'primarily' the 

 recognition of an unconformity between the 

 Carboniferous and Permian in England ; and 

 secondly, the correlation of a portion of the Salt 

 Range strata of India as intermediate between 

 these two ' systems ' of the English column. 



In the Cenozoic six 'systems' are cited, viz : 

 Eocene, Oligocene, Miocene, Pliocene, Pleisto- 

 cene and Recent ; but we are told in the text 

 that these are hardly systems in the sense in 

 which the term is used in the case of the older 

 rocks. Further on, the chapters describing 

 these formations are headed as follows : 

 ' The Eocene Rocks,' 'Oligocene and Miocene 



