388 Miscellaines. 
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 
originals 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 ;—WMonoclinate, the right — 
rhomboidal and oblique rhombic prisms ;—Diclinate, the oblique rec- 
tangular prism ;—T'riclinate, 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. 
