Environs ofLons le Saunter. 149 



into beds of conchoidal flint (silex conchoides), it afterwards 

 re-appears io regular and very thin beds. 



Above it are seen, first in a compact limestone, afterwards 

 in a granular limestone, very beautiful, smooth, and striated 

 terebratulas, of the size of a pigeon's egg; they are assembled 

 in groups, and adhere but slightly to the rock. 



They are associated in the granular limestone with en- 

 trochi and echinites; the entrochi are so abundant, that they 

 form the greater portion of many beds ; terebratulae, not so 

 well preserved as the former, are again mixed in it, with 

 certain undetermined bivalves, of which the interior cast 

 only is found. 



Beds of large grained oolite occur at this height ; around 

 the grains, the rock forms concentric layers, which leave no 

 doubt of the contemporaneous formation of the grains and 

 their matrix. 



This rock is sometimes hard enough to receive a good 

 polish ; its colour is grey, siightly blueish, but the edges of 

 the bed and fissures are of a yellowish white colour; this last 

 tint is produced by the alteration of the former, by the in- 

 increased oxidation of the iron it contains, wherever water 

 has been able to penetrate. 



This alteration of colour is seen in many quarries of build- 

 ing stone in the Jura ; a kind of natural ornament in the 

 buildings results from it, producing a very beautiful effect. 

 It may particularly be observed in the town of Besan9on. 



To the limestone full of terebratulae and entrochi, succeed 

 beds, slightly shelly, of white oolitic and granular limestone, 

 furnishing the best building stone in the country. 



Quitting these beds, no more granular limestone is found 

 to the second stage of the oolite formation. 



Very thick beds of compact limestone alternating with 

 oolites, constitute the top of the first stage. 



This compact limestone is white; its fracture, at first 

 undetermined, becomes, as it rises, more and more con- 

 choidal ; in the upper beds it is brittle, and its fragments 

 are very sharp. 



