150 GEOLOGY. 



are doubtless a variety of tlie trachytic rocks ; but it is 

 curious that, even when studied in the cabinet, the 

 author of the paper has evidently been in great doubt as 

 to whether they were of sedimentary or volcanic origin, 

 and has preferred the former opinion. Having merely 

 rock specimens, Dr, Sadebeck has classed together-, under 

 the general head ^of eruptive rocks, granites, porphyries, 

 and basalts — a view not in agreement with the observa- 

 tions made a little further to the east ; for it is evident 

 that all the granites observed belong to a far more 

 ancient series of rock formations than the basalts. 



