Chemical Science, 



479 



Pottery. 



Nevers. Paris. Ger»ovia. 



(i.) (ii.) (iii) 



Silica 0.572 0.541 0.544 



Alumina 0.124 0.127 0.220 



Lihie 0.226 0.0fi3 0.064 



Oxide of Iron 0.066 0.070 0.098 



Magnesia 0.024 0.038 



Water 0.173 0.020 



"0.988 0.998 7^984 



(i.) Earthenware of Nevers — Paste of a pale red. Made of a 

 marie occurring close to the town ; the glaze is a white enamel, 

 containing both tin and lead. 



(ii.) Paste of the brown earthenware made by M. Husson at 

 Paris. The biscuit is red, but is covered by a brown glaze, co- 

 loured by oxide of manganese. 



(iii.) Red earthenware resembling the Etruscan, and found in 

 the ruins of Gergovia near Clermont. 



Crucibles, &c. 



St. u 



Hessian. Paris. English. Etienne. Nemours. Bohemta. Crenaot. 



(i.) (ii.) (Tii.) (iv.) (V.) (vi.) (vii.) 



Silica 0.709 0.646 0.637 0.652 0.674 0.680 0.680 



Alumina 0.248 0.344 0.207 0.250 0.320 0.290 0.280 



Oxideof Iron.. 0.038 0.010 0.040 0.072 0.008 0.022 0.020 



Magnesia trace .. .. trace trace 0.005 trace 



Water 0.103 0.0 10 



0.995 1.000 0.987 0.974 1.002 0.99T 0.990 



(i.) Hessian crucibles — formed of a clay very aluminous, with 

 which siliceous sand is mixed. They sustain rapid changes of 

 temperature without fracture, but cannot retain fused litharge very 

 long together, and have too coarse a grain for many purposes. 



(ii). Paris crucibles, manufactured by Beaufaye — they are made 

 from the clay of Andennes, near Namur; part of the material 

 being baked and coarsely powdered, and the rest in its natural 

 state : no sand is mixed with it, and the inner surface of the ves- 

 sels is finished with a thin coat of the unbaked material. They 

 are said to be more refractory than the Hessian vessels, not more 

 liable to fly by change of temperature, and more retentive of 

 litharge. 



(iii.) Fragment of an unbaked crucible prepared for an English 

 cast-steel work, 



(iv.) Paste with which the crucibles are made for the steel 

 works of Berardiere, near St. Etienne. 



(v.) Fragment of a used crucible from the glass works of Ba- 

 gneaux, near Nemours ; it had been made from the clay of Forges 

 (Seine Inferieure). 



(vi.) A used crucible from a Bohemian glass-house. 



(vii.) Bricks with which the blast furnace* at Creusot are con- 



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