REVIEWS AND BOOK NOTICES 459 



lowed by those who are not deeply versed in mathematics, as only the sim- 

 pler formulae are introduced. In the summary at the close of this chapter 

 on evolution, after a word of warning that this theory should not be accepted 

 as final, since many phenomena having a critical bearing upon it are yet 

 to be developed. Dr. Moulton says: 



The development of a spiral nebula by the near approach of two suns seems 

 to be a necessary consequence, though this point needs further elaboration. The 

 development of some such a system as ours from a small spiral nebula of the type 

 considered seems to be inevitable. So far as the details have been worked out, 

 nothing directly contradictory to the theory, or even seriously questioning it, 

 has been found, while it explains admirably all the main features of the system. 

 It can be safely said that, at present, this hypothesis satisfies all the requirements 

 of a successful theory much better than any previous one. 



The final chapter is devoted to stars and nebulas in which, as before, 

 the selection of the important things is notable. The work is to be heartily 

 commended to the geologist who wishes a brief and trustworthy summary 

 of the recent developments in astronomical science. T. C. C. 



A Preliminary Report on a Part of the Clays 0} Virginia. By Hein- 

 RiCH RiES, Ph.D. (Geological Survey of Virginia, Bulletin 

 No. II, 1906.) Pp. 184, 15 plates, 10 figures. 



The investigation of the clays of Virginia has been well begun, and 

 when completed it is proposed to pubHsh a volume on the clay industries 

 of the state. So far attention has been confined to the coastal plain belt. 

 The expressed purpose of this work is to determine (i) the extent, quaH- 

 ties, and apphcabihty of the clays; and (2) whether the clays now beino- 

 utilized could be used 'for making other and better products than are now 

 being made from them. To this end many samples were collected and 

 carefully investigated both chemically and physically. The results of 

 these investigations together with instructive discussion of the origin, 

 properties, and mode of occurrence of clay, methods of mining and manu- 

 facture, etc., are embodied in this report. 



The first chapter, forming Part I of this report, treats of the "Geology 

 of the Virginia Coastal Plain" and was contributed by William Bullock 

 Clark and Benjamin LeRoy Miller. The interpretation of the Sunder- 

 land and other Pleistocene formations is given in unqualified terms as 

 though unquestioned science, with no intimation to the reader that the 

 interpretation is questioned and other interpretations advanced. The 

 pubhc are entitled to know the true state of the case. E. W. S. 



