568 —— - Reviews— Whitaker's Geology of London. 
limestones may be taken as an example. There is a section on 
Contact Metamorphism, which, together with general remarks on 
Metamorphism, and two Appendices, completes the work. 
Dr. Irving is a professed disciple of Credner, and has made free 
use of his writings, as well as of the German literature of the subject 
generally, nor has he been forgetful of the writings of Hnglish 
petrographers in the construction of his treatise. In addition to 
this he combines his own considerable experiences as a geologist in 
the field and as a chemist in the laboratory. There can be no doubt, 
therefore, that much interesting and valuable matter is contained 
in these pages. Moreover, few will disagree with the statement in — 
the preface that the truest teaching is that which stimulates the 
mind to active thought, not that which saves the student the trouble 
of seeking by loading the memory with second-hand knowledge. 
All this is excellent, but when he talks about a tendency to fetter 
the discussion of scientific questions by a spurious orthodoxy, Dr. 
Irving is again tilting at a windmill. The two schools which 
respectively put their trust in diagenesis and epigenesis enjoy the 
most perfect freedom of discussion at the Geological Society, and 
that they make ample use of it any one who is in the habit of 
attending the meetings can testify. 
Il.—Tue Gerotocy or Lonpon anp or Part or THE THAMES 
Vatiey. By Wittiam Waurraxer, B.A., F.R.S. Vol. I. 
Descriptive Geology, pp. xii. 556, Folding Table. Price 6s. 
Vol. II. Appendices (Well-sections, etc.), pp. iv. 852. Price ds. 
Geological Survey Memoir. 8vo. (London, 1889.) 
EVER before has the geology of any tract of country been 
described in such detail. We say this advisedly, bearing in 
mind other publications (the result of private or of official enterprise), 
whose object has been to describe as fully as possible the geclogy of 
particular areas. There is good reason why London should yield 
such ample information, and it is fortunate in having so enthusiastic 
and so careful an exponent of its geological record. 
In the country around London there have been more numerous 
exposures of the strata than elsewhere, in the foundations for houses, 
not to mention the excavations for gravel, clay, and chalk, and the 
railway-cuttings. Moreover, not only has the surface structure been 
revealed in so many places, but the underground geology has been 
proved in the numerous wells and borings, several of the latter 
being very deep, and furnishing information of high geological 
interest. Hence no other part of the world could have contributed 
such a mass of geological facts. 
To begin at the end of the work, we may mention that the records 
of well-sections (given in Vol. IJ.) number nearly 800; and in 
addition there are notes of numerous trial-holes and many other 
sections. This volume in itself will be of great practical value to 
well-sinkers and other engineers; but notwithstanding the mass of 
information he has so carefully arranged and tabulated, with all 
authorities indicated, the author still craves for more—asking for 
