89 



In the secondary class, no order is to be as- 

 signed, from the limited number of substances 

 contained in it, and from the frequent alternations 

 in which these are found. 



The following 1 list contains, in confirmation of 

 the preceding views, a few examples of the differ- 

 ent orders of succession which occur among 

 rocks. The examples are all selected from this 

 country, partly for the purpose of increasing the 

 authority of the statements, by permitting them 

 to be easily verified, and partly for that of facili- 

 tating the access of the student to a set of facts 

 which are at variance with some of the received 

 geological systems. The localities have been 

 added for the former reason ; and they might 

 easily have been multiplied had it .appeared ne- 

 cessary. Geologists have recently ascertained 

 that similar uncertainties of arrangement exist in 

 other countries, and the student may consult their 

 writings. The examples are not quoted: as, 

 throughout this work, it has been deemed expe- 

 dient to rely as far as possible, only on those facts 

 respecting which the author imagines he has re- 

 ceived that conviction which is founded on ob- 

 ervation. 



