MODE IX. GYPSUM. 



there are icthyolites; the impression of the fish 

 being compressed, as in schistus : nor are the 

 fish solid, as in limestone. 



" M. d'Arcet possesses an ornitholite, or pe- 

 trified bird, which he found, in 1781, twenty 

 fathoms below the summit of Montmartre *. 



" It has not yet been decided to what species 

 of animals the bones found in gypsum belong. 

 If these bones are neither agatised, nor pene- 

 trated with gypsum, it is because the absorbent 

 earth, which forms their base, is found to be 

 combined with phosphoric acid, and a fat sub- 

 stance j-j consequently the selenitic water has 

 not been able to decompose these bones. 



" The brown hepaltic iron ore, solid, in an 

 irregular mass, which is found dispersed in some 

 places in the hill of Montmartre, seems to be 

 the product of decomposed pyrites. 



" The calcareous and gypsous Iudi 9 in a 

 spheroidal mass, flattened, called by the work- 

 men miches de quatorze sous, are found to the 

 east of Montmartre, near Clignancourt, in a bed 

 of marl, from twelve to fifteen feet below the 

 summit of the hill. Among the ludi of this 

 kind, which are in the cabinet of the royal 

 School of Mines, there is a spheroidal mass, 



* It seems to be a water-rail. 



\ The acidum pingue is a favourite teet of M. Sagc> 



