June 19, 1896.] 



SCIENCE. 



903 



most beautiful of all geometrical sciences — the 

 study of the exact forms assumed by crystalliz- 

 ing substances. 



In the little volume before us the author lias 

 ■endeavored to give the beginner in crystallog- 

 raphy an insight into the subject in its various 

 branches. The book occupies the same place 

 in German scientific literature as does Dr. 

 Williams's Elements of Crystallography (Holt & 

 Co.) in English literature. It goes further 

 than the latter book, however, in that it treats 

 of the physical as well as of the geometrical 

 properties of crystals. 



The order of treatment iu the volume is not 

 quite as logical and consecutive as one would 

 wish it to be in au elementary text-book. It 

 opens with an ' Introduction ' in which the gen- 

 eral principles of geometrical crystallography 

 are described (rather than discussed). In this 

 portion of the book such subjects as coordinated 

 axes, symmetry, zonal equations, parallel 

 growths, twinned crystals and pseudomorphs 

 are explained, some of which, it would seem, 

 might better have been left unexplained until 

 the student had mastered the characteristics 

 of simple crystals. 



The discussion of the six crystal systems 

 occupies 132 pages — about one-half the volume. 

 The discussion of each begins with a brief study 

 of the symmetry of the holohedral forms; then 

 follow the descriptions of the individual forms 

 and of their simple combinations ; and in con- 

 clusion the description of the hemihedral and 

 tetartohedral forms. The derivation of the 

 partial forms from the holohedral ones is not 

 ■emphasized as it is in Williams's book. They 

 are treated rather as forms in which certain 

 planes of symmetry have disapjDeared. 



The last 100 pages are devoted to an outline 

 treatment of physical crystallography. - The 

 figures used here are well chosen to illustrate the 

 text. All of them are fresh and some are en- 

 tirely original. This portion of the volume de- 

 serves more extended notice than can be given 

 it in this place, not because the subject-matter 

 is startling in its novelty, but because the sub- 

 ject of which it treats is made so little of in 

 this country, whereas, in reality, familiarity with 

 it is indispensable to a true knowledge of the 

 properties of crystals. 



The chapters on hardness, etching and optical 

 properties are especially interesting. Here 

 more particularly than elsewhere will the 

 student wish that the author had explained 

 the logic of the conclusions reached through 

 the study of the phenomena described. The 

 chapter on the optical properties of crys- 

 tals covers this difficult branch of crystal- 

 lography in a very satisfactory general man- 

 ner. The treatment is not full enough to 

 enable the student to understand the optical 

 methods of studying crystals, but it is sufficiently 

 thorough to enable him to understand the prin- 

 ciples upon which the methods are based. 



The magnetic, electrical and thermal proper- 

 ties of cr_. stals are next briefly referred to, and 

 the volume closes with a condensed statement 

 of the relations existing between crystals and 

 their chemical composition. ' 



On the whole, the book is an excellent 

 introduction to modern crystallography ; it 

 is certainly the best book of its kind pub- 

 lished in any language, and yet one can- 

 not help feeling that the author has not pro- 

 duced a book that will serve ' fiir Studirende 

 und zum Selbstunterricht. ' In the hands of an 

 instructor it should unquestionably serve a use- 

 ful purpose and should make an excellent text- 

 book. 



The colored plates illustrate the appearance 

 of the axial figures of crystals, the dichroism of 

 tourmaline, etc. , and the pyro-electrical proper- 

 ties of quartz, boracite and struvite. 



W. S. B. 



Chermotheca Italica Continens Exsiccato, in Situ, 

 Coccidarum Plantis, Precipue Cultis, in Italia 

 Occurrentibus, Ohnoxiarum. Cocciniglie rac- 

 colte in Italia. Fascicolo I. Pkof. Antonio 

 Beelese e De. Leonaedi Gustavo. Por- 

 tici. 1896. Lire 10. 



For a number of years sets of dried fungi 

 have been published by mycologists in this 

 country and abroad. The earliest works of 

 this description were issued in Europe. The 

 first distinctively American effort in this direc- 

 tion, as I am informed by Mr. B. T. Galloway, 

 was made by H. W. Ravenel, of South Caro- " 

 lina, who published his Fungi Caroliani Exsic- 

 cati from 1852 to 1860. Other writers, especi- 



