266 VII. EARTHS AND ALKALIES.— 



requires another luting over it to keep it moist, and prevent its 

 cracking ; also for pottery, for lining ponds, and for modelling. 



Devonshire blue clay. Makes white solid pottery, but is 

 expensive. 



Devonshire black clay. Fat, tough ; makes cream ware. 

 Devonshire cracking clay. Grey, burns to a beautiful 

 white, but is apt to crack in the firing. 



Common clay, Argilla latei'itia. Drying, astringent, used 

 for artificial stones, as bricks, &c. and common pottery. 



Fullers* earth, Cimolia purpurescens^ Smectis, Terra sapo- 

 naria, Terra fullonica. Greyish brown, but varying greatly, hard, 

 very compact, rough, but scrapes glossy, does not colour, burns 

 hard and yellowish brown ; being very fine, and absorbing grease 

 very readily ; used to full woollens. 



Rotten stone, Terra cariosa. Ash brown, very light, mode- 

 rately hard, dry, colouring, burns to a deep ash, but no harder ; 

 Derbyshire ; used as a pohshing powder. 



Umber, Terra Umhria, Greta Umhria. Fine pale brown, 

 close, very light, dry, colouring, burns deep reddish brown, but 

 no harder ; used as a colour, and to give porcelain the shining 

 ground called ecaille. From Turkey. — Burnt umber. Used for 

 paint ; makes a good shade for gold : both are excellent dead 

 colours, having a good body. 



Windsor loam, Hedgerly loam. Yellowish brown, very 

 hard, heavy, harsh, colouring slightly, burns very hard and fine 

 deep red ; from Hedgerly near Windsor ; used for setting the 

 bricks of wind-furnaces, glass-house furnaces; also for making 

 lutes, and coating glass and earthen vessels to be exposed to a 

 strong fire. 



Bath bricks. Windsor loam made into bricks ; used for a 

 coarse polishing powder. 



Founders' clay, Penny earth. Dusky brown, very hard, 

 heavy, harsh, not colouring ; Woolwich, also Northamptonshire ; 

 used for moulds in large founderies. 



Cheam clay. Very light ash-colour, nearly white, compact, 

 fine, very smooth, not colouring, burns pale white and very hard ; 

 used for the body of glazed gallipots. 



Bohemian Tripoli, Poller schiefer, Creta cinerea^ Schistus mollis, 

 Terra Melia. Light ash-colour, heavy, moderately hard, open, 

 harsh, dusty but not colouring, not altered by burning ; used for 

 polishing, and as a plate powder. 



Terke verte, Terra viridis. Deep bluish green, very heavy, 



