290 DESCRIPTION OF THE MUSEUM. 



stances impregnated with it, or is composed of 

 such as contain its principles. It is thus that the 

 beautiful semi-transparent group, in the bottom 

 of this case, was formed, which came from the 

 manufactory of M. Curaudau. The greater num- 

 ber of the varieties on the stage is also produced 

 by artificial crystallization. 



The following species, the alkaline fluate of 

 alwnine, also called cryolite, is of no use in the 

 arts ; but is interesting to the mineralogist on 

 account of its rarity. The shelves, next to the 

 stage for study, present a very precious series of 

 the different varieties of cryolite, all remarkable 

 for their size, and were brought from Green- 

 land by M. Giesecke, professor of mineralogy at 

 Dublin. This learned professor employed nearly 

 eight years in exploring, with indefatigable zeal, 

 a country still new to the naturalist, and col- 

 lected an abundant harvest of various produc- 

 tions, with which he has been pleased to enrich 

 the collection of our Museum. 



(Eighteenth and nineteenth cases). We are 

 now arrived at the second class of minerals, that 

 of stones, or earthy substances. These produc- 

 tions are generally of brilliant and beautiful 

 colours ; amongst them are classed those rare 

 and desirable stones which art transforms into 

 objects of dress and ornament. In the first place, 



