OF PAPA STOUR 



171 



of porphyritic slaty-felspar. On the west side of 

 the island, it covers beds of breccia and amygda- 

 loid. To the . eastward of Hirdy-gio, it is in the 

 form of a conglomerate, containing angular mas- 

 ses, having the cement and fragments of similar 

 composition and appearance. At Little-Peatie's- 

 gio, the compact-felspar is covered with breccia, 

 and a rock of felspar that contains much quartz. 

 The compact-felspar, in some instances, contains 

 crystals of disintegrated felspar and steatite. It 

 is usually massive 5 but it seems, upon assuming 

 the porphyritic structure, to have a slaty struc- 

 ture ; as near Hirdy-gio, where the slaty frac- 

 ture is very distinct. 



CLAYS TONE. 



This rock chiefly occurs at a place called Stain, 

 between Houseavoe and Olisvoe. It is of a bluish- 

 grey colour. The beds are moderately thin, not 

 much inclined, and considerably decayed, as ap- 

 pears by numerous fissures or rents which traverse 

 them. It contains crystals of red felspar, thus 

 forming porphyritic-claystone. Two curious va- 

 rieties of this rock are here to be observed : the 

 first is a claystone-conglomerate, containing an- 

 gular fragments of the claystone, connected by an 

 impure cement of claystone, mixed with mica 

 and sand : in the second variety, the claystone 

 occurs in the form of globular distinct concre- 

 tions, connected by a softer basis than the con- 



