INDEX. 471 



PAGE 



Plastic clay, Mr. Buckland on the beds of ... 277 



, account of the beds of near Reading . . 282 



, near London . . 284 



on the coast of Sussex . 294 



their connexion with those of France 298 



Plumsted, account of the Plastic Clay beds near . . 290 



Plymouth, Mr. Hennah's observations on the limestone of . 410 



Porphyritic veins, of St. Agnes. Rev. J. J. Conybeare on . 401 



— — — probably contemporaneous with 



the schistose rocks which they traverse . . . 402 



' appearance of the schist in con- 



tact with them . 403 



Porphyry of the Cheviot hills described .... 93 



veins of, traversing the schist and granite of Cruachan 121 



generally appear perpendicular 121 



of Cruachan, its varieties described . . . 122 



■ shews a regular series of transition from 



porphyry to trap . . . . . . . 123 



Potter's clay, found immediately below the soil over the coal 



measures ......... 10 



Quartz, beds of, interstratified with the marble limestone of Sky 167 



Mr. Phillips on the primitive crystal of . . 233 



— on the cleavage of .... 247 



Quartz rock and schist series of Sky, described . . . 161 

 ■ alternates repeatedly with red sand- 

 stone 162 



, Dr. Mac Culloch's supplementary observations on 264 



■ , circumstances to prove that its origin is partly 



mechanical . . . . • 268 



, avanturine a variety of 272 



. — } particulars of its occurrence in Sky . . . 273 



, alternations of, with red sandstone and greywacke 



schist *~i 



Quicksands, covering the coal measures .... SO 



3 o 2 



