Such a transition of one substance into another essentially different, not by decomposition and the consequent loss of one of the component parts of the substance; not by another kind of decomposition, in which the loss of one of the component parts of the substance is spontaneously replaced by another, thus giving rise to a new compound; but by the introduction of a new principle, by the combination of new constituent molecules with those of which the integrand molecules of a substance are previously composed; would be so highly interesting, and lead to consequences so new, so remote from every thing presented to us in the mineral kingdom, and at the same time so important to the science of geology, that it requires to be examined with the most scrupulous attention. Accordingly I shall reserve the further consideration of this subject for the observations which will conclude this memoir.
Observations on the Primitive Crystal, and Integrant Molecule of Bardiglione.
In my enumeration of the specific characters of bardiglione, I have said that its form was a rectangular tetrahedral prism with a square base, fig. 1; in which the absence of additional faces, either at the edges or angles of the terminal faces, had not hitherto permitted me to determine the height. I added, that this prism was divisible in a direction parallel to its two diagonals, as pointed out in fig. 4, which shows at the same time, that each of the primitive rectangular tetrahedral prisms is composed of four right trihedral prisms, the bases of which are right angled isosceles triangles, fig. 3. The height of these trihedral prisms remains equally unascertained, and they constitute the integrand molecule of this substance, fig. 2.
