224 Analyses of Books. [Sept. 



and abuts against either the old sandstone, or even the nearly- 

 horizontal beds of the limestone series. 



8. On the Strata in the Neighbourhood of Bristol. By Richard 

 Bright, M.D. &c. With Notes extracted from the Communica- 

 sions of Geoi'ge Cumberland, Esq. 



Note on Magnesian Breccia. By Henry Warburton, Vice- 

 Pres. of the Geol. Soc. 



9. On the Magnesian Limestone and Red Marl, or Sandstone, 

 of the Neighbourhood of Bristol. By W. H. Gilby, M.D. 



These papers contain further additions to the history of the 

 rocks which form the subject of the two former communications. 

 The district of which Bristol is the centre presents all the mem- 

 bers of the series of British strata from the old sandstone upwards 

 to the lias limestone ; viz. the old sandstone, the encrinal lime- 

 stone, the coal formation, the magnesian limestone, the red marl, 

 and the lias limestone. The encrinal limestone of this district is 

 sometimes, it seems, covered by conformable strata of magnesian 

 limestone abounding in shells, entrochi, and madrepores. 



The strata of the beds up to and including the coal formation 

 are more or less elevated, and it is on the edges of these that 

 the horizontal beds of the limestone conglomerate are deposited. 

 This conglomerate in some places is of common limestone, and 

 in others contains more or less of magnesian limestone. Of 

 this conglomerate there appear to be two beds, incumbent on 

 which are the marls and calcareous sandstones that form the 

 red marl deposit. This latter, besides presenting the usual 

 characters of the rock, includes veins and nodular masses of 

 sulphate of strontian. 



15. Description of a Series of Specimens from the Plastic Clay, 

 near Reading, Berks, icith Observations on the Formation to 

 which those Beds belong. By the Rev. W. Buckland, Professor 

 of Mineralogy in the University of Oxford, &c. 



The plastic clay formation in its most extended sense includes 

 the series of beds which exist between the chalk and the London 

 clay in England, and the chalk and the calcaire grossier of the 

 basin of Paris. 



The immediate covering of the chalk is an alluvium of rolled 

 and angular flint pebbles mixed more or less with sand and 

 green earth ; and at Reading, and in some other parts contain- 

 ing a peculiar species of oyster, together with small teeth of 

 fish. Above this, lie various beds of sand and sandy loam, 

 among which is a bed of fuller's earth ; but the principal repo- 

 sitory of this useful mineral is the sand below the chalk. 

 The middle and upper part of the series is more clayey ; 

 and the uppermost bed is a loose sand supporting the London 

 clay. This bed of sand in the London basin is filled with water, 

 from which all the deep wells of the metropolis are supplied in 

 inexhaustible abundance. Mr. Buckland's paper contains 

 various interesting particulars respecting this deposit both in the 

 London basin and on the coast of Sussex. 



