193 



CHAP. XIII. 



i 



SYNOPTICAL VIEW OF THE GENERAL CHARAC- 

 TERS OF THE FAMILIES OF ROCKS CONTAINED 

 IN THE PRESENT ARRANGEMENT. 



IT has already been remarked, that, according to 

 the geological arrapgement here adopted, where 

 many distinct mineral compounds must some- 

 times be arranged under one general title, no 

 condensed descriptions or definitions of the fami- 

 lies can be given. Such descriptions can only 

 be expected in the catalogue of varieties ; the 

 characters of the family being, in fact, contained 

 in the preliminary remarks by which each of 

 these is preceded. 



But as, in some cases, a certain general mine- 

 ralogical character will be found to pervade the 

 whole family, it has been judged expedient t3 

 bring these into one condensed view, as far as 

 was practicable, addingto them an abstract of such 



