l^nvirons ofLons le Saunter. tdil 



GRYPHITE LIMESTONE FORMATION. 



» Rapid examination of the beds it contains. 



The first visible beds of this formation are earthy and 

 imperfectly schistose marls, of a deep grey colour, almost 

 black, containing subordinate beds of red gypsum, the frac- 

 ture of which presents curved bundles of small crystalline 

 plates ; the gypsum also forms contorted veins which follow 

 the undulation of the laminae of marl, and the strings that 

 cwt them, and lastly occurs much mixed. 



After an unknown but considerable height of these gyp- 

 seous marls, there exists a thickness of from six to eight 

 metres [26 feet] of compact whitish argillaceous limestone, 

 formed of thin and perfectly even strata. 



The gypseous marls again follow, then very marly gypsum, 

 less red than the preceding, the beds of which are separated 

 by beds of marl, subordinate in their turn to the gypseous 

 matter. 



Continuing to rise, many masses of gypsunt are met with 

 separated by pure marls or gypseous marls ; the gypsum, 

 with some few exceptions, becomes more pure ; its colour 

 becomes paler, and passes by successive shades into clear 

 red, rose colour, grey, and white; the thickness of these 

 beds increases, whilst the beds of marl that separate them 

 become thinner; the crystalline faces diminish in size, and 

 end by disappearing entirely. 



The last mass, furnishing the finest plaster, contains beds 

 of three metres [nearly 10 feet], and even, in some places, 

 five metres [16y feet] thick; no trace of gypsum is again 

 found to the summit of the last formation of the Jura moun- 

 tains. 



I know not if, as yet, any species of organic remains has 

 been discovered in these masses of gypsum. 



There exists above the gypsum rocks a great height of 

 marls, characterised by their varied colours ; their section, 

 sometimes discovers in the transverse gorges, ribbon like 



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