REVIEWS 87 



The physical classification of the minerals is based on streak, color, 

 cleavage, and hardness. Under the description of each mineral, besides 

 the ordinary physical characteristics, there is a note on its associations 

 and occurrence. The use of cleavage in the classification seems to be 

 helpful for the determination of those specimens which show good 

 cleavage; but for those lacking cleavage, it is in some cases necessary to 

 search through several sections before the mineral can be determined. 

 For example, if a specimen of magnesite shows good cleavage, it can be 

 identified readily in section 7; but if it happens to be of the white, 

 massive, unglazed porcelain-like variety, it is not found in the section 

 containing minerals with no cleavage, and search must be made through 

 from one to three other sections to find it. 



The method of classification adopted saves many pages, and if the 

 principle is clearly understood, should result in little confusion. 



D. J. F. 



Fossil Plants, Volumes I-IV. By A. C. Seward. Cambridge: 

 University Press, 1898-1919. 



Seward's great textbook deals only with Thallophyta, Pteridophyta? 

 and Gymnospermae. The printing is excellent, but there should be more 

 illustrations. Each volume has an excellent index and an exhaustive 

 bibliography. Since twenty-one years elapsed between the appearance 

 of the first and the fourth volumes, there is naturally unevenness in the 

 publication. While the last two volumes are up to date, the first two 

 are somewhat antiquated. 



This is now the standard textbook of the paleobotanist. The 

 volumes deal not only with external structures, but also with the ana- 

 tomic and morphologic features. In short, the book attempts to be a sur- 

 vey of our present knowledge of paleobotany. Every student of the 

 subject will have to start from Seward, no matter what topic touching 

 cryptogamic and gymnospermic plants he may approach. 



A comparison with Schenk's Handhuch naturally forces itself upon 

 the reader. There is no doubt that Seward's work is a great advance 

 on Schenk's, although the latter is still an authority on fossil angiosperms. 



If we compare the usefulness of Seward's book with, for instance, 

 Zittel-Eastman's volume on Invertebrates, we cannot escape the convic- 

 tion that Seward's book is not intended for determinations. There is 

 still need for a handbook of paleobotany which can be used by the 

 collector for determining fossil-plant genera and, if possible, species. 



A. C. N. 



