PREFACE. 



I HAVE endeavoured in the following pages 

 to collect much valuable Geological information, 

 which was scattered through several volumes of the 

 Annales des Mines, a work edited by the General 

 Council of Mines at Paris ; and it is hoped that by 

 thus presenting it in a portable form, it may be found 

 useful to English Geologists, by enabling them easily 

 to compare some of our own rocks with similar forma- 

 tions described in the above work ; a correct know- 

 ledge of the changes which take place in many rocks, 

 particularly those of the secondary class, in their 

 mineralogical structure, &c. at different distances, 

 being I conceive not one of the least important 

 branches of geological inquiry. 



In order to avoid a repetition of synonymous terms, 

 I have prefixed a Synoptical Table of Equivalent 

 Formations ; the arrangement adopted has been 

 simply that of convenience, and 1 wish it to be clearly 

 understood that it is no attempt at geological divi- 

 sions : from the alluvium to the greywacke and its 

 associated beds, the rocks are placed in the order of 



