294 M. BaoNGNiAnT on the Magnesite, Sfc. 



calcareous and magnesian formations. The first deposJtes, 

 those which are nearest the spring, this able chemist tells 

 uSj are also those most charged with peroxide of iron and 

 silex ; the limestone, still ferruginous, then follows, and is 

 the more pure and more separated from these two sub- 

 stances, the more distant it is from the point where the 

 spring rises from earth ; the carbonate of magnesia is the 

 last deposited. 



Without wishing to establish any real resemblance be- 

 tween this succession and that of our rocks ; without wishing 

 to represent that these rocks, certain beds of which shew 

 too clearly the characters of mechanical aggregation for them 

 to have been formed by solution, have been deposited by 

 the mineral waters of the ancient world, we cannot avoid 

 remarking that commencing with the chalk, we find a series 

 of rocks, the nature and succession of which are nearly the 

 same as those which M. Berthier has observed in the depo- 

 sites from mineral waters. Thus, 1st, a new formation, i.e. 

 a new emission of dissolved matter would appear to com- 

 mence above the chalk, at first depositing silex and iron, 

 represented, one by the beds of sand and sandstone, and 

 the other by the iron ore found so abundantly iu the de- 

 posites of lignites and plastic clays which cover the chalk ; 

 2dly, the more or less compact limestone, accompanied by 

 iron and silex in the lower beds, and by silex in the upper 

 beds; 3dly, the magnesite also accompanied by silex, which 

 still occurs in the lower gypsum beds ; this silex is partly 

 soluble in alkaline liquids, like that of the calcareous depo- 

 sites of certain mineral waters ; 4thly, the gypsum, the most 

 soluble substance of all those we have named, and which 

 should be the last deposited. 



We do not pretend to draw any other conclusion from 

 these different resemblances ; but it appeared to us right 

 to hazard them, if it were only to engage the attention of 

 chemists and geologists. 



