134 



DESCRIPTION OF TlNTQ^ 



namely, that there are alternations between the 

 oldest members of the Floetz rocks, and the newest 

 portions of the Transition series,--correspondin^ 

 to a similar relation, which has been observed be- 

 tween the newest Primitive and the oldest Tran- 

 sition rocks. We thus learn, that the newest 

 members, for example, of the primitive, do not 

 immediately cease, or at once give place entirely 

 to the transition rocks ; but that, most frequently, 

 before these are found completely to prevail in the 

 order of succession, alternations, as now mention- 

 ed, take place. And the remark may be gene- 

 ralized respecting the junctions of all the succes- 

 sive classes in the system, down to those of the 

 latest periods. 



The account I have given of the structure of 

 Tinto, approaches perhaps as near the truth, as the 

 geognostic inspection permitted by the state of its 

 surface, authorises. Future investigation will no 

 doubt, correct or improve it. I cannot hope, that 

 it will be found to contain much that is particularly 

 interesting to the mineralogist. It records no oc- 

 currence of rare or precious minerals, — no irre- 

 gular junctions, dislocations, or extraordinary phe- 

 liomena of stratification, to raise the as^:onishme^t 



