REVIEWS 727 



character of the Tremadocs as passage beds from the Cambrian to the Ordovician, 

 especially in view of the fact that it is only in this country that they are placed in 

 the former instead of the latter. The separation of the Lower Devonian into 

 Dartmouth slates, Meadfoots and Staddon grits, which is now recognised by the 

 Geological Survey, is ignored, while many far less important divisions are elsewhere 

 recorded. The author does not recognise a continental period between the 

 Cretaceous and Eocene, though he admits that the Eocene sea probably " did 

 not extend much beyond the present chalk escarpment." One would have 

 thought that the smallness of the area in which the Thanet sands appear to have 

 been laid down was satisfactory evidence that in early Eocene times the sea was 

 confined within much narrower limits. 



A word of protest must be entered here against the author's inclusion of 

 Pleistocene and Recent deposits in the Tertiary, an innovation that does not 

 apparently meet with his colleague's approval, for the latter speaks on p. 217 of 

 "Tertiary and post-Tertiary eruptions." A Quaternary or Anthropozoic period 

 can be justified on the score of both convenience and principle. The post- 

 Pliocene deposits that are open to our observation are as a rule superficial 

 deposits in terrestrial areas and most of a widely different character from those 

 which have been preserved to us from earlier times. The epoch when man 

 began to exercise an important influence on the world's history marks the 

 inauguration of a series of changes as great as those which divide the Palaeozoic 

 from the Mesozoic or the latter from the Kainozoic. There is every reason to 

 believe that even during the course of the Pleistocene he was the cause of some 

 striking modifications in the distribution of life upon the globe and this process 

 has since proceeded with ever-increasing rapidity and extent of operation down 

 to the present. With the increase of population, of agriculture and of mining 

 (more especially the exploitation of alluvial deposits), even purely physical changes 

 have become more and more pronounced. The commencement of the glacial 

 period, during which the pre-existing surface accumulations over a large portion 

 of the earth's surface were removed and redistributed directly or indirectly by the 

 action of ice, has been generally adopted as a suitable point at which to draw a 

 dividing line between the Tertiary and Quaternary ; there seems no good 

 reason for disturbing this convention and with it the accepted grouping and 

 nomenclature of the later deposits. 



These criticisms must not, however, be understood as detracting to any 



appreciable extent from the value of what is a thoroughly readable and useful 



account of British stratigraphy. 



John W. Evans. 



A Course of Practical Work in Agricultural Chemistry for Senior Students. 



By T. B. Wood, M.A. [Pp. 56.] (Cambridge : At the University Press, 

 igii. Price 2s. 6d. net.) 



In his preface, Prof. Wood states that the subject-matter of this booklet has been 

 used at Cambridge, in the form of type-written sheets, for the last ten years. If 

 that be so, he should have published it long ago, for there is no doubt that 

 its usefulness will be appreciated in a much wider sphere than the Cambridge 

 laboratory. 



Every department of practical agricultural chemistry is well represented and 

 it is impossible to quarrel with the material chosen, even though some of the 

 experiments seem hardly up to a standard for "senior students." The greater 



