138 M. Chasb AVt on the 



manner, so that a very considerable mass, with a mean di- 

 rection of N.N.W. & S.S.E. (onze heures) has been turned to 

 the E. ; and lastly, that this mass has been again cut trans- 

 versely at the spot intersected by the town of Lons le 

 Saunier. To avoid entering into long details, I shall con- 

 tent myself by noticing that throughout the extent of this 

 basin, from the foot of the platform to Montmorot, the 

 ground is, in a measure, furrowed in similar longitudinal 

 masses, contiguous and cut transversely like the first. 



Portions of these masses that are not broken, have re- 

 mained at the bottom of the basin, uniting at their base the 

 separated hills which enclose it. The town of Lons le Saunier 

 is built on these portions of masses, consequently on the 

 edges of the upset beds of the gryphite limestone formation. 



This is the place to mention the salt spring that rises in 

 the town itself. 



In no point of this canton is the saliferous gypsum obser- 

 vable, the muriate of soda of which is dissolved by rain 

 water, and gives birth to this spring ; it is however certain 

 that it exists in the interior of the formation. I mean to 

 examine if the knowledge of the nature of the ground may 

 not lead to the determination of the place containing the 

 saline rock. The hills in the environs of the town do not 

 expose any outcrop of gypsum, but every thing shews that 

 the knoll of Pimont contains it ; I have noticed an elevated 

 ridge of gryphite limestone on this knoll, covering a con- 

 siderable thickness of variegated marls ; now, in all the 

 gypsum quarries of the Jura, the masses of this rock occur 

 precisely under these same marls ; it may therefore be pre- 

 sumed that masses of gypsum exist in this knoll, but that 

 they are masked by the debris of a more recent formation, 

 which covers the lower part of the variegated marls, begin- 

 ning with the coal bed. 



This conjecture acquires additional support from the 

 existence of a small spring of selenitous water, which 

 breaks out precisely at the lower part of the variegated marl 

 beds. I shall here state that this spring supplies the foun- 

 tain of the abbey, the waters of which are known in the 



