Review of Dana's Mineralogy. 369 



Andalusite. The mica from Jones' Creek, near Baltimore, con- 

 tains opaque lines or bands in concentric hexagonal figures which 

 arise from the same cause, p. 54. 



Section 11. Crystallogeny. — This section is divided into two 

 parts. 



1. The theoretical part, containing the various theories which 

 have been adduced to account for the structure of crystals, and 

 a particular illustration of that which appears to be most consis- 

 tent with facts. 



2. The practical part, including the different processes of crys- 

 tallization and the attendant circumstances. 



The original and profound views of the author on the follow- 

 ing questions — " What are the laws by which molecules are su- 

 perimposed on molecules in perfect order, and these tiny yet won- 

 derful specimens of architecture constructed ? What is this crys- 

 tallogenic attraction ? What the nature of the ultimate particles 

 of matter ?" — are unfolded in the early part of this section. He 

 gives in the first place, a succinct account of the history of the sub- 

 ject, which is one that has exercised the ingenuity of the most pro- 

 found philosophers. It has been before said in this Journal, (Vol. 

 xxxn, p. 388,) that " after much examination of this matter, we do 

 not hesitate to declare our opinion, that this mysterious problem, 

 which since the days of Epicurus has been so often unsuccess- 

 fully attacked, is at length here solved/'* It is a satisfactory cir- 

 cumstance that this somewhat bold conclusion has been borne 

 out by the evidence of so great an authority as M. Necker, who 

 has fully recognized the correctness of Mr. Dana's views. (Bib- 

 liotheque Universelle.) 



Under the heads of isomorphism and dimorphism, the recent 

 views of Dr. H. Kopp are introduced, (p. 88,) as well as those 

 of Mitscherlich and Rose. 



" Isomorphism. — The isomorphism of certain substances must be at- 

 tributed to some similarity in the nature of the molecules, in conse- 

 quence of which they produce, in their combinations, compound mole- 

 cules of similar ellipsoidal form and similar axes. Lime and protoxyd 

 of iron are thus allied, and the qualities of their molecules are so alike, 

 that, on uniting with the same substance in like proportions, the com- 

 pound molecule has nearly or quite the same form, and similarly ar- 



* Mr. Dana's article on the formation of crystals, may be found at length in this 

 Journal, Vol. xxx, p. 275. 

 Vol. xlvi, No. 2.— Jan .-March, 1844. 47 



