IBIS.] On the forsiation of rocks. -2cI^ 



and is not found in mountainous countries. Bucli is 

 tlie gypsum round Paris^ at Luneburgli^ and in Hoi- 

 stein. Perhaps some of the extensive formations of 

 gypsum in Spain^ and that in the vicinity of Jena^ in 

 Saxohy, may belong to this formation. 



TThe remains of animals have, I believe, only been 

 found, as yet, in the extensive gypsum quarries in the 

 vicinity of Paris 5 in almost any other situation, except 

 the vicinity of a large town, it is probable that the few^ 

 specimens containing such organic matter might have 

 remained unnoticed for ages ; which shoAvs how defi- 

 cient \ve are in the necessary knowledge of the actual 

 state of the substances w ithin the reach of our observa- 

 tion ; and how faW are the positive facts on which the 

 narrow foundation of our general and sweeping sys- 

 tems of the earth's formation must rest* 



14. Coarse-grained Shell Limestone^ consist- 

 ing of the remains of organic matter, which are 

 now only found to exist in water, sufficiently proves 

 its Neptunian origin, as well as that of all its 

 accompanying strata; the silex found alternating or 

 touching this formation^ has often the impressions of or- 

 ganic matter, and has always the structure of the sili- 

 ceous precipitates found in the first order of the Nep- 

 tunian rocks. 



This formation generally occupies the lower levels : 

 it is seldom found in mountainous countries ; it covers 

 immediately both primitive and other more recent for- 

 mations ; it is found both in extensive and partial beds ; 

 and varies only in tlie nature of the shells it contains ; 

 the rock itself beins much the game, either a coarse 



