368 Count de Bournon 071 BardigUone. 



Such a transition of one substance into another essentially difFerent, 

 not by decomposition and the consecfuent loss of one of the com- 

 ponent 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 com- 

 pound ; but by the introduction of a new principle, by the combi- 

 nation of new constituent molecules with those of which the integrant 

 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 

 BardigUone^ 



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 tetra- 

 hedral 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 consti- 

 tute the integrant molecule of this substance, fig. 2. 



