1814.] Werner/an Society. 149 



extensive stratum containing shells, which appears at Woolwich, 

 and in many other parts of the London basin. South of the Thames, 

 are also con'^idered by Mr. Webster as portions of the upper ma- 

 rine formation. Beds containing similar fossils, occur in the Paris 

 basin, covering the gj'psum and gypseous marls of the lower fresh 

 water formation. 



The above strata in the Paris basin, are covered by very extensive 

 and thick beds of a pure sand, sometimes loose, sometimes con- 

 creted ; with which is also connected that peculiar and valuable 

 mineral, known by the name of meidiere, or burr-stone. In the 

 Isle of Wight, there is nothing to correspond with these important 

 beds except a tiiin layer of sand ; but in the counties round Lon- 

 don, there occurs in detached blocks, a very silicious sandstone cal- 

 led the grei/ iveathers, which has been largely'employed in archi- 

 tecture, and which is co'.ijectured by Mr. Webster to be of cotem- 

 poraneous origin with the French sandstone. 



The upper fresh water formation^ one of the most remarkable 

 and best characterized of any of the English beds, above the blue 

 clay, is best seen at Hendon, in the Islt: of Wight. Its thickness 

 is about 55 feet, and though not subdivided into distinct strata, it 

 varies considerably in texture. Much of it consists of yellowish- 

 while marl, more or less indurated, but friable and crumbling by 

 frost. Many of the shells imbedded in this stratum are quite 

 entire, consisting of various species of lymneas, planorbes, helices, 

 and other fresh water shells. Over this bed is a stratum of clay 

 with small bivalv« shells, covered by a bed of yellow clay without 

 shells, which latter is covered by a bed of friable calcareous sand- 

 stone, also without shells. To this succeed other calcareous strata 

 with a few fresh water shells, varying much in compactness from 

 that of chalk to porcellanous limestone. 



This formation appears to have covered nearly all the northern 

 half of the Isle of Wight. 



In the Paris basin are strata corresponding with these both in 

 their general composition and in the fossils which they contain, 

 distinguished however by certain peculiar characters that are de- 

 ' tailed by the author of this paper. 



WKRNERIAN SOCIKTY. 



At the first meeting of the sixth session of this Society, held on 

 the 20th of November, the Secretary read a communication from 

 Mr. Hisinger, of Sweden, containing an analysis of the variety of 

 brown spar denominated spatli perlce. He fouul that 100 parts 

 contained 



Lime 27'97 



Magnesia 21-14 



Oxide of iron 3'40 



Oxide of manganese 1 '50 



Carbonic acid 44*()0 



Loss 1-39 



100-00 



