302 DESCRIPTION OF THE MUSEUM. 



before us. Watch chains and snuff boxes are 

 made of it, as also mirrors for telescopes, cru- 

 cibles, and small instruments for the use of 

 mineralogists. 



Gold has hitherto been found only in the native 

 state. In the Brazils it is met with regularly 

 crystallized, as appears from the beautiful spe- 

 cimens with which M. Geoffroy enriched the 

 Museum. It more often exists in a ramified state 

 on the surface of apparently common stones, 

 the ground of which is a white or yellowish 

 quartz. It is disseminated in grains amongst the 

 sand of several French rivers, such as the Rhone, 

 the Arriege, etc. In the thirty-sixth case we 

 may observe an enormous piece of massive gold, 

 from Peru, it weighs five hectogrammes, or six- 

 teen ounces and a quarter, French w eight. 



Native silver, like gold, exists under the form 

 of twisted filaments on the surface of certain 

 stones ; when in contact with air it loses the 

 lustre it has immediately after it is taken from 

 the mine ; its surface is soon tarnished and co- 

 vered with a blackish coating. We see in the 

 bottom of this case a fine specimen of p^tivc 

 silver, brought from Mexico by Donibey. 



In the thirty-seventh case are the different 

 combinations of silver with sulphur and anti- 

 mony, and the carbonic and muriatic acids. Above 



