ACCOUNT or THE ROCKS NEAR DUNDEE. 139 



ef the same height, independent of the variety 

 pf rocks, forming a steep bank on the north side 

 of the river Tay. In this bank, there are some 

 important sections of the strata displayed, which 

 I propose to describe. 



Where the sandstone begins at the east side of the 

 bay, it occurs in thin strata dipping to the north* 

 west, at an angle of about 1^°. This sandstone 

 soon disappears, when a mass of porphyry forms 

 the bank. Its western extremity is but indis- 

 tinctly displayed ; its eastern extremity is cover- 

 ed with sandstone. This porphyry has a slaty 

 structure in the great, is composed of a basis of 

 compact felspar, and contains numerous crystals 

 of common felspar, and a little basaltic horn- 

 blende. The sandstone soon gives place to the 

 porphyry which rises below it, and forms the pre- 

 cipice for a considerable distance. East from the 

 Boothe, there is a mass of sandstone interposed, as 

 represented at fig. 2. 



d 2 3 4^ s e r S ^ 



The porphyry, fig. 1., is disposed in strata about 

 fJur feet in thickness. It is traversed by a vein 

 containing calc-spar, brown- spar, and sparry-iron- 

 stone, — minerals which are nearly related, both in 

 their oryctognostic and geognostic characters. Tbe 



