Dr. KiDD on the Mineralogy of St. David's. 81 



of the cliiTs which they compose a bold but graceful curvature, very 

 characteristic of a coast of this kind, and productive of scenery the 

 most magnificent. A very striking illustration of this effect, though 

 it is not clear whether it proceed from rocks of this class or from 

 those more immediately belonging to the coal grits, occurs at 

 Saunders' Foot, a small cove situated about four miles to the north- 

 east of Tenby. 



It not unfrequently happens that the partial removal of the 

 superincumbent laminse of the schist, from the surface of those 

 placed relatively beneath them, has given rise to that appearance of 

 a succession of broad flat steps or stairs which suggested to the 

 Swedish mineralogists the term Trapezius ; a term applied by them 

 to that class of rocks, in which from the action of the weather and 

 other causes, there is a tendency to assume an appearance of this 

 kind. 



These slaty strata are occasionally traversed by beds of clay 

 porphyry ; and by veins of quartz affording very large and beautiful 

 specimens of rock crystal. 



It is worth noticing that in none of the stratified or unstratified 

 rocks of this neighbourhood, did the extemporaneous test of an acid 

 give any evidence of the presence of carbonate of lime : nor did 

 there occur in them, with the exception of one equivocal instance, 

 th& smallest trace of any organic remains. 



St, David's Head. 



The rock which forms this promontory consists of a mixture 

 of blackish green hornblende and white felspar ; but the pro-- 

 portion of the hornblende often so far predominates, and its cry- 

 stalline form is so regularly developed, that the felspar appears rather 



Vol. II. i 



