86 Count de Bournon o« //j^? Laumonlte. 



it may commit, an attempt has been made to insinuate its uncertainty 

 and even its inutility. But wliat science is there which would not 

 be annihilated the moment that we made its truth and its usefulness 

 to depend on the exact degree of correspondence that might subsist 

 between the opinions of those philosophers who make it the subject 

 of their study ? If there exist some difference in the opinions 

 entertained by the AbbeHaliy and myself on certain points in crys- 

 tallography, what conclusion ought to be deduced from this cir- 

 cumstance ? simply that this science, which on the one hand is sup- 

 ported by physics, and on the other by mathematics, and will 

 perhaps at some future day become equally exact with the latter, 

 has not yet obtained that certainty. Let us allow it to proceed to- 

 wards this point, without obstructing its course. Difference of 

 opinion when maintained with candour and decorum is perhaps not 

 without advantage to the security and promptitude of its progress. 



General ohservations on the Laumonlte, 



The laumonlte has never hitherto been discovered except in a 

 crystallized state, either in separate crystals, which is the most com- 

 mon appearance, or in an aggregation of crystals, forming masses of 

 more or less considerable size for the most part irregular, and deeply 

 striated externally. 



Till the present time the laumonlte had been observed only in the 

 lead mine of Huelgoet in lower Brittany, in w^hich it was discovered 

 about twenty-five years ago by M. Gillet de Laumont.* 



* It lines the walls of the vein, conjoiiilly v,-ilh a lamellar carbonate of lime belonging 

 to that variety in which the rhomboidal fragments are striated in the direcdon of the 

 greater diagonal of two of the oj)positc faces. This carbonate of lime, which is perfectly 

 colourless, is one of the most phosphorescent which I have ever seen. If I nwy jndg? 



