78 Count de Bournon on the Latimonite. 



In the first appendix to his " Tra'ite de Mineralogie^^ that cele- 

 brated mineralogist, who was then disposed to consider it as a 

 variety of the mesotype, states that he was induced to regard its 

 primitive crystal as a rectangular tetrahedral prism, having indications 

 of subdivision in the direction of its two diagonals ; but since in his 

 subsequent work, entitled, " Tableau comparatif des resultats de la 

 Crystallographie et de V Ajialyse chimtque^'' &c. p. 49. he has changed 

 his opinion, and has declared its primitive crystal to be a rectangular 

 octohedron, having its faces unequally inclined. The observations, 

 which I have myself made on this substance, prevent my assenting 

 to either of these two forms as its primitive crystal ; and they have 

 enabled me at the same time to present to the Geological Society a 

 more complete examination and description of it. The possibility 

 of my doing so I owe to the friendship of M. Gillet de Laumont, 

 who lately sent me several specimens, among which was one of very 

 considerable magnitude. On its way to me it was broken. Chance, 

 which very frequently assists the observer when he is prepared to 

 profit by it, produced by that accident what I should certainly never, 

 have attempted myself: it furnished me with an immense number of 

 fragments, and of perfectly regular crystals, and at the same time by 

 exposing to view the central part of the mass, which had never yet 

 been acted upon by the atmosphere, and had therefore been pre- 

 served entirely unaltered, it enabled me to examine this substance 

 before it had undergone any kind of change, a circumstance which 

 must of necessity be but of very rare occurrence. 



