1 6 Yorkshire Boulder Committee : Seventeenth Year's Work. 



Reported by The Thirsk Naturalists' Club, 

 per J. E. Hall, Secretary. 



Thirsk. 



In gravel pit, Gabbro (Carrock Fell), porphyrite (Cheviot 

 type), Shap granite, Oolite (not local), Carboniferous con- 

 glomerate (Roman Fell type), granite. 



Upsal, Wool Moor. 



725 ft. o.D. _ ■ 



Dolerite, millstone grit, black limestone. 



Upsal, Hag's Hill. 

 225 ft. O.D. 



Gabbro (Carrock Fell). 

 Granite (? Cheviot). 



A. \^ery frequent throughout district. 

 Carboniferous limestone, black and encrinital. 

 Canister. 



Chert. ' ■ r 



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 tuff (? Cheviot). 

 Gabbro (Carrock Fell). 



Remarks. 



Dividing our district into three longitudinal strips roughly 

 Codbcck (central), Sv^ale (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 K. and W. 



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

 confined to the central district. 



Naturalist, 



