388 MisceUaines. 



without being able to determine what is the particular primary form. 

 To these systems of crystallization, the author has applied the fol- 

 lowing nomenclature, partly derived from other authors and in part 

 original; viz. the Monometric, including the cube, regular octahedron 

 and rhombic dodecahedron ; — Dimetric, the right square prism and 

 square octahedron; — Trimetric, the right rectangular and rhom- 

 bic prisms, the rectangular and rhombic octahedrons; — Tetraxonal, 

 the rhombohedron and hexagonal prism ; — Monoclinate, the right 

 rhomboid al and oblique rhombic prisms ; — Diclinate, the oblique rec- 

 tangular prism ; — Triclinate, the oblique rhomboidal prism. The 

 laws for the occurrence of secondary planes are explained with much 

 particularity and illustrated by an extensive series of figures. Next 

 follow remarks on the lettering of figures of crystals and an explana- 

 tion of the system adopted by the author, which every one will see, is 

 vastly preferable to the method (if it deserves the name,) which now 

 prevails. We have no room to state it, but we can confidently say 

 that its general adoption would save the student much perplexity, 

 (since a mere inspection of a figure thus lettered, informs him on 

 what edges or angles the secondary planes there given are situated,) 

 and would also greatly facilitate the comparison of different figures. 

 The chapter on the means of detecting the primary forms of crystals, 

 by goniometrical measurements, observation of cleavage, situation 

 of secondary planes, &.c. is quite extensive and satisfactory. It is 

 followed by one treating of compound crystals and of aggregations of 

 imperfect crystals. 



We now come to the section on Theoretical Crystallogeny, in 

 which, after a brief history of the science, the author unfolds his own 

 original views of the ultimate structure of crystals. These were first 

 made public in the thirtieth volume of this Journal. After much ex- 

 amination 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 unsuccessfully attacked, is at length here solved. Many 

 facts which at first seem to be exceptions to the universality of the 

 laws which this discovery develops, are shown to be its legitimate 

 and even necessary results ; and many curious phenomena which no 

 other theory can interpret, are by this beautifully explained. Enough 

 is already known to ensure the stability of this new theory ; the pro- 

 gress of discovery, will, we are sure, only contribute new confirmation 

 of its truth. A brief chapter on Practical Crystallogeny concludes 

 this Part. 



