88 



rock produces similar uncertainty ; or rather, 

 perhaps, this ought to be considered as an unques- 

 tionable proof of the irregularity in the succession 

 of the primary rocks. It is, plainly, but the same 

 fact expressed in different language. 



Where, however, alternations are clearly visi- 

 ble, as in those cases where strata of limited extent 

 follow each other with a conformable inclination 

 and in contact, no constant order can be found ; 

 or rather, the greatest irregularity seems to pre- 

 vail. 1 shall, to illustrate this statement, here 

 subjoin a catalogue of some of the most remark- 

 able alternations among the primary strata as they 

 occur in Scotland. Some of these are limited to 

 one succession ; in others, the alternations are re- 

 peated ; but it is unnecessary for the present pur- 

 pose to distinguish them. 



The order adopted in the catalogue is there- 

 fore arbitrary in the primary class ; and has only 

 been selected, as being the most conformable to 

 established habits ; but it comprises certain alte- 

 rations that became requisite in consequence of 

 the adoption of a different division, and of a new 

 member. 



