4 3 O F E A R T H S. 



At a place called Black Shcel-Bog, near a coal-work, two miles 

 fouth from Haltiveftl, is an argillaceous pale yellow earth, mixed 

 with white, and fpanglcd with flat talcy particles. It is unctuous, 

 in handling, flightly colours the fingers, and is eafily broken. 

 In the mouth it is gritty, and of a naufeous tafte, which goes off 

 with a kind of fweetnefs. In a glafs of water it burils into a 

 powder, and Mains it with a bright yellow. Depurated, and 

 worked into a pafte, it is of the fame colour, and of great tena- 

 city. It does not efFervefce with Aquafortis. In the fire it acquires- 

 a ftony hardnefs, and a light red colour, variegated with white, 

 looking like a marble. The, floors of the Roman ovens at their 

 flation of Caervorran feem to have been made with it. It is ufed 

 by fkinners and glovers in drefling and colouring their leather ; 

 for which ufe it is carried in great quantities fo far as Wejlmor- 

 land. 



There is a vein of the fame kind by the brick clay-pit near the 

 High-Sheels on Hexbam-common , many loads of which are car- 

 ried to Newcajlk for the ufe of the fame trades. It is a fpecies of 

 Fuller's earth. 



At Weft Thurfton, near Felfon, is an argillaceous earth of an afh- 

 colour. It is of a denfe compact texture, unctuous to the touch, 

 melts flowlyonthe tongue, with a little grittinefs; breaks and 

 moulders in water with difficulty. Depurated and worked into 

 a pafle, it afTumes a milk-white colour, and cuts through with a 

 glofTy furface, and on being fmoothed with a knife, has a fine 

 fkin when dry. It does not efFervefce with Aqua fortis. In the 

 fire it acquires a dull white colour. It is ufed at the glafs-houfes 

 in Ne-wcajlle for making furnaces, or veflels, that will bear an 

 intenfe fire ; for which ufe it is not inferior to any in Britain, in 



the 



