■28 WISCONSIN ACADEMY SCIENCES, ARTS, AND LETTERS. 



United States may be readily made. The anal3'ses in Table I of 

 Wisconsin kaolins are those already given, and have the same num- 

 bers as before. 



In Table II., analyses I., II., III., IV., V., VI., and VII., are taken 

 from the " Geology of New Jersey, pp 683-688. I. is the average 

 composition of the best white clay of the Cretaceous, near South 

 Amboy, analyzed just as taken from the pit. II. is the clay from 

 Trenton, New Jersey, Jinalj'zed after washing to free from quartz 

 sand, also Cretaceous. III. and IV. are clays imported from Coblentz, 

 Germany, for making glass-pots. V. and VI. are the St. Louis, Mo., 

 glass-pot clay, raw and prepared. VII. and VIII. are New Jersey 

 potters-clays (Cretaceous), and undergo some vitrification on burn- 

 ing. Analyses IX. to XIX. are taken are taken from Percy's Metal- 

 lurgy, Volume on Fuels, p. 99. IX. is a true kaolin from Pool, Dor- 

 setshire, used in making Cornish crucibles. X. is also a true kaolin, 

 from Ireland. Small crucibles made from it were kept for 

 hoars with melted steel in them, without changing form. XI. is 

 also an Irish kaolin. XII. and Xlll. are the finest Cornish kaolini 

 .analyzed by different chemists — washed before analyzing. XIV, is 

 the best Stourbridge fire-clay; XV. a poorer kind of Stourbridge 

 clay, XVI. is the best Dowlais clay; XVII. a poorer Dowlais clay. 



XVIII. is a greenish kaolin, with red spots, from Newcastle, Dela- 

 ware; used for making glass-pots and porcelain saggars. Analyses 



XIX. to XXV. are from the Indiana Geological Report for 1874. 

 XIX., XX., and XXI. are the Lawrence county, Indiana, porcelain 

 clay, analyzed raw. XXII. is Irom Golconda, Illinois; occurs in 

 pockets in the Carboniferous rocks. XXIII, is washed Chinese 

 kaolin. XXIV. is washed kaolin from St. Yrieix, France. XXV. is 

 Missouri " ball clay." XXVI. and XXVII. are kaolins from Saarau, 

 Silesia, analysed raw and washed; quoted from the second supple- 

 ment to Watt's Chemical Dictionary p. 354. In comparing the 

 Wisconsin clay with these foreign clays it should be borne in mind 

 that for porcelain making the qualities desired are whiteness after 

 burning and refractoriness to heat; and for making firebrick refrac- 

 toriness only. The coloration will increase directly with the con- 

 tent of oxyds of iron. The refractoriness will decrease* with the 

 increase of the ratio of fluxes (iron protoxyd, lime, magnesia, pot- 



* Watt's Chem. Dictionary, Second Supjjlament, p. 354. 



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