364 Review of Dantfs Mineralogy. 



Plagionite. Pyrosclerite. Fichtelite. 



Voltzite. Thrombolite. Konlite. 



Greenockite. Variscite. Hartite. 



Faujasite. Krisuvigite. Ixolyte. 



Malthacite. Kammererite. Guyaquillite. 



Ottrelite. Fossil copal. Berengelite. 



Pelokonite. Middletonite. Pigotite. 

 Praseolite. 



It is surprising, considering the correctness of this treatise 

 on its first appearance, to find how numerous and important 

 are the changes which have been made in the present edi- 

 tion. 



In the volume already quoted, we have given a full outline of 

 the plan and general arrangement of Mr. Dana's work, which it 

 is the less necessary to repeat at present, since the first edition is 

 in the hands of so many of our readers. The mathematical ap- 

 pendix of the first edition is omitted in most of the present one ; 

 only a few are bound up with it for the satisfaction of those who 

 wish to pursue that portion of the subject. Notwithstanding 

 this omission, the present edition is considerably larger than the 

 former — the whole amount of new matter being little short of 

 one hundred and fifty pages. It is in fact to all intents and pur- 

 poses a new book, modelled on the general plan of the former, but 

 altered in many important points to suit it to the present advanced 

 state of the science. Without farther preface, therefore, we pro- 

 ceed to give in as condensed a form as possible some of the novel 

 features of greatest interest which strike our eye in the work, 

 following the order of the contents. 



Irregularities of Crystals. — Under this head, (which consti- 

 tutes the 3d chapter,) we have an important addition, and an 

 able exposition of a subject which is the cause of much per- 

 plexity to the student, and, when rightly understood, unfolds 

 many difficulties and apparent anomalies, both in the form and 

 composition of minerals. The irregularities of crystals are treated 

 of under four heads. 1. Imperfections of surface ; 2. Variations 

 of form and dimensions ; 3. Internal imperfections and impurities; 

 4. Pseudomorphous crystallizations. Under the first head we 

 have — 



1. Striated Surfaces. — "These are produced by minute planes cov- 

 ering the surfaces striated, and usually inclosed parallel to the seconda- 



