76 
SCIENTIFIC NEWS. 
able bodies when they combine, and the orderly arrangements 
* of which produces symmetrical crystals. These will, no doubt, 
be very useful, particularly to such as are unacquainted with 
mathematics, and might, on that account, be scarcely, without 
such assistance, enabled to study this interesting department of 
science. The designs which accompany the work, give 
the complete figures, and render the models not indispensable, 
but supplementary, for more readily understanding the subject. 
The wood-cuts, which amount to upwards of 100, and plates 
introduced into the work, in illustration of the laws of the 
science, render the crystallographic models superflous to those 
who are familiar with geometry and linear perspective. The 
graphic designs of the crystals have been traced by the method 
of projections ; the entire lines represent the edges or outlines 
of that part of the solid immediately turned towards the 
observer 5 and the dotted lines express those edges which are in 
the opposite part of the solid, and which of course the observer 
could not see, unless the solid were diaphanous. 
The work is divided into 4 parts, and each part is again subdivid- 
ed into sections. The first part of the Treatise is introductory to 
the 3 following, and is divided into 4 sections. It treats on the 
general nature of the process of crystallisation— the disposition 
of crystallisable materials of different kinds, to assume a certain 
number of geometrical forms, peculiar to them, and no others— 
the rectilineal interior structure of crystalline solids, their 
increase or growth, stating it to take place in such a way that 
every thing which existed at each period of growth of a 
crystal, remains fixed, and so as to present on all sides a basis as 
it were for the crystallisable materials which arrive for con- 
taining the edifice, and thus contrasting it with the growth of 
organic beings, and general definition and objects of the science 
of crystallography. 
The 2d section exhibits the practical means by which 
crystallisable materials are made to assume symmetrical forms, 
the crystallisation of saline, metallic, and other bodies, as it is 
induced by the processes of solution, fusion, sublimation, 
chemical affinity, &c. The circumstance which influences the 
crystalline processes — the ratios of crystalline energies in 
different bodies — its admeasurement and other practical state- 
ments relating to the artificial crystallisation of bodies. 
The 
