ON ERRATIC BLOCKS OF THE BRITISH ISLES. 235 



Reported hy the Thirsk J^aturalists' Club, per Mr. J. E. Hall, Secretary. 



Thirsk. — In gravel pit — 



Gabbro (Carrock Fell), porphyrite (Cheviot type), Shap granite, oolite (not 

 local), Carboniferous conglomerate (Roman Fell type), granite. 



Upsal, Wool Moor, 725 feet O.D.— 

 Dolerite, millstone grit, black limestone. 



Upsal, Hag's Hill, 225 feet O.D.— 



Gabbro (Carrock Fell). 

 Granite (? Cheviot). 



A. Very frequent throughout district. 



Carboniferous limestone, black and encrinital. 



Ganister. 



Chert. 



Millstone grit* 



Dolerite. 



B. Fairly frequent throughout district. 



Andesitic breccia. 

 Cleaved andesitic breccia. 



„ „ ash. 



„ ,, ,, with epidote. 



„ ,, rhyolitic breccia. 



„ „ agglomerates. 



„ ,, purple breccia. 



Shap granite. 

 Vein quartz. 



C. Occasional. 



Cheviot porphyrite. 

 Carboniferous conglomerate. 

 Volcanic tufE (? Cheviot). 

 Gabbro (? Carrock Fell). 



Remarks. — Dividing our district into three longitudinal strips, 

 roughly, Codbeck (central). Swale (western), edge of Hambletons (eastern), 

 we find Class A pretty evenly distributed. 



Class B very frequent in the central district and only occasional in 

 the E. and W. 



Class C, so far as our research goes, are almost entirely confined to the 

 central district. 



Gravel Pits, Thirsk — 



Cheviot porphyrite, 3. 

 Carboniferous conglomerate, 4. 

 Shap granite, at least, 30. 



Gravel Pit at Pickhill — 



Carboniferous conglomerate, 1. 



Shap granite also found at Richmond, Swaledale, and Wemmergill, 

 Lunedale. 



