450 Analyses of Books. [June, 



scovany, when composed of a mixture of quartz and chlorite ; not 

 very liard : calpy, when composed chiefly of hard quartz, cohmred 

 bv a little chlorite : pryavy, when the ore does not occur in a com- 

 pact state ; but mixed with the constituents of the lode : grauanyy 

 when composed chiefly of granite. 



Vil. On the Fresh Water Formations in the hie of Wighty 

 with some Observations on the Strata over the Chalk m the south- 

 east Part of England. By Thomas Webster, M. G. S.— One of 

 the most remarkable additions which geognosy has of late years 

 received, is an accurate description of the beds which cover the 

 chalk in the neighbourhood of Paris. These beds abound in petri- 

 factions ; by a careful examination of which it has been ascer- 

 tained that some of these beds have been formed at the bottom of 

 the ocean, while others, placed above them, have been formed at 

 the bottom of a fresh-water lake ; and these alternations are 

 repeated more than once : so that the sea appears to have twice 

 covered the environs of Paris, to have twice retreated while its 

 place w-as supplied by a fresh-water lake. Immediately over the 

 chalk lie the following beds: 1. plastic clay"; 2. coarse lime-stone 

 and sand-stone ; 3. siliceous lime-stone, which have been formed at 

 the bottom of the sea. Next comes a bed of gypsum, marl, &c. 

 containing only bones of land animals and fresh- water shells, and 

 therefore formed at the bottom of a fresh-water lake. It consti- 

 tutes the lower fresh-water formation. Then come beds of marl, 

 containing only sea shells, and therefore of marine formation. It 

 constitutes the upper marine formation. The sixth bed consists of 

 sand and sand-stone, without shells; the seventh a sand-stone 

 containing sea shells ; the eighth, the buhr or mill-stone forma- 

 tion, without shells, and argillaceous sand. Then comes the upper 

 fresh-water formation, comprehending marls and buhrs, with fresh- 

 water shells. This last formation is covered by alluvial soil. For 

 a particular description of these formations we are indebted to 

 Brogniart and Cuvier. 



Though the south-east of England bears this striking resemblance 

 to the north of France, where the Paris basin is situated, that its 

 basis is chalk, which is covered in various places by different beds, 

 yet Mr. Webster was the first person who pointed out a similarity in 

 the formations in certain parts of the south-east of England and 

 those which fill up the Paris basin. The two places where the 

 resemblance is greatest are the Isle of Wight basin and the London 

 basin. In the Isle of Wight Mr. Webster traced an alternation of 

 sea and fresh-water formations similar to those near Paris, and 

 characterized by the very same fossils. The beds, indeed, are not 

 exactly the same in both, though there is a certain degree of re- 

 semblance between them. These different formations can be dis- 

 tinctly seen at Headen Hill, upon the north side of Alumbay, not 

 far from the Needles, on the west coast of (he Isle of Wight. Sir 

 Henry Englefield first discovered a range of chalk-hills running 

 east and west through the middle of the Isle of Wight. These hilU 



