ACCOUNT OF THE ROCKS NEAR DUNDEE. 143 



Strata composed of chemical precipitates, all the 

 variety of inclination depends on the inequality 

 of the bottom and in this they are confirmed, 

 not so much by attending to appearances in small 

 portions of roclis, such as here described, as by an 

 examination of the structure of mountain masses. 



These few remarks certainly lead to little that is 

 precise or important in the history of the strata^ 

 now described. They indicate, however, the in- 

 timate relation which subsists between the sandstone 

 and "the claystone. This relation, I had previously 

 ascertained in my examination of the Island of Papa 

 Stour ^ ; and the observations which I have recent- 

 ly made on the south bank of the Tay, tend still 

 further to confirm and illustrate it. At Flisk- 

 wood, directly opposite to the north bank of the 

 river, where the appearances detailed above 

 are exhibited, the sandstone covers the claystone* 

 Here the sandstone rests upon very soft clay-por- 

 phyry, which passes into claystone. This clay- 

 stone at last becomes more compact, assumes the 

 amygdaloidal structure, and then becomes con- 

 nected with compact felspar. 



These appearances seem to indicate the ex- 

 istence of a family of floetz-rocks, consisting prin- 

 cipally of claystone, felspar, and sandstone, the 

 relations of which are but imperfectly under- 

 stood. 



J WOTerian Memoirs^ vol, i. p. 16^, 



