DESCRIPTION OF TINtO. iBi 



With regard to the environs of Tinto, the ris- 

 ing ground called the Castle Hill, about a mile 

 from the foot of the mountain, on the south-east, 

 Consists, as far as I could ascertain, from the 

 minute croppings it affords, of greenstone, 

 which, I presume, trends eastward to a consider- 

 able distance, the quarry near the church of Sy- 

 mington having uncovered a bed of that substance. 

 This greenstone is probably nev^^er than the grey- 

 wacke, which I suppose lies beneath the base of 

 Tinto, 



On the Castle Hill, I found a variety of frag- 

 ments and rolled masses, which serve to illustrate 

 the nature of the rocks in this district : grey- 

 wacke, common flinty-slate, flinty-slate with veins 

 of quartz, felspar- porphyry with a violet hue, 

 and specks of a greenish matter somewhat re- 

 sembling the newly designated Pimelite of Kar- 

 sten ; also sandstone with casts, and a very com- 

 pact brecciated stone, having a basis approaching 

 to greenstone, and including fragments of quartz, 

 iron-clay and jasper. 



Amygdaloid, another member of the floetz class, 

 is the rock which forms the bed of the river, at 

 the new bridge erected over the Clyde, on the 

 road to Biggar. Its base is wacke, and it is sur- 

 rounded by beds of fine-grained and compact 

 sandstone, coloured with green earth. The vesi- 

 cles are filled with nodules of calcedony, coated 

 with green earth, and having quartz in the 



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