GEOLOGICAL COLLECTION. 263 



according to their relative ages. Each of them 

 is represented by its principal and subordinate 

 rocks, to which are added the most abundant or 

 remarkable organized fossils contained in the 

 formation. Besides these, after each rock with 

 its organic remains, are placed all the vegetables, 

 articulated animals and mollusca, which are too 

 small to be properly seen in the cases of the 

 first room. Lastly, that nothing may be wanting 

 to complete the history of each formation, spe- 

 cimens of the metalliferous or sterile veins, most 

 frequently found, are added to each rock which 

 contains them. By going round the glass cases 

 we may form a very good idea of the above 

 collection, which has been thus summarily ex- 

 plained. We must begin at the end near the 

 entrance. We first observe specimens of pri- 

 mitive formations, they are rocks entirely formed 

 of crystallized mineral particles, generally hard, 

 and never containing organic remains ; precious 

 stones and minerals are contained in them. 



Immediately after these are specimens of tran- 

 sition formations, a knowledge of which is no 

 less important, as they are almost as rich in metals 

 and polishable masses as the preceding ; they 

 shew besides the volcanic productions of the first 

 ages of the world, and the vestiges of the first 

 organized beings. 



