Earthenware. 601 



by being very slightly fusible while, felspar is particularly so, and 

 granite is one of the most fusible of known rocks. It probably owes 

 its present state to that infusibility at a time when the aggregation 

 of the more fusible rocks, with which it is associated, took place. 



6. The principal material in the Earthenware is the finer kinds of 

 clay found in Dorsetshire and Devonshire, but which as they are too 

 aluminous to stand the operation of drying and baking without crack- 

 ing, are mixed with a large proportion of silica derived from grinding 

 calcined flints to an impalpable powder, whence it derives the name 

 of " Flint- ware," by which it is most properly distinguished. Of this 

 ware are formed plates and dishes, and articles of the same kind. 



7. In a former Report I have shewn, that kaolin earth abounds in 

 the red marie formation of Mysore, of a quality as fine, or perhaps 

 finer than Cornwall affords, and in quantities which are inexhaust- 

 ible, and have proved its fitness for the manufacture of Porcelain, by 

 using it in the preparation of crucibles capable of bearing the very 

 highest heat of a very powerful blast furnace, with a very slight 

 degree of softening, and by which they become merely baked into a 

 kind of coarse porcelain of a very pure white colour. 



8. That South India abounds in clays of every variety of purity 

 and colour, cannot be doubted, though the subject has never yet 

 been properly investigated. 



9. The common red calcareous clay used by the native potters is 

 well known to every one, but the ware which they manufacture from 

 it is quite unable to stand a heat above redness, from the readiness 

 with which one of the ingredients (carbonate of lime) combines with 

 silica and alumina, giving off at the same time its carbonic acid, 

 which causes the fused clay to assume the form of a spongy, bubbly 

 mass. 



10. The fact of the carbonic acid being thus given off, proves that 

 the carbonate of lime is only in the state of a mechanical mixture 

 with the other ingredients, and not in chemical combination ; whence 

 is certain, that it may be easily removed by the action of acids upon 

 the clay, (perhaps cheaply by employing the common country vinegar,) 

 and the clay thus fitted for firing at high temperatures. 



11. The natives who flux a mixture of white quartz and crude 

 soda for making a coarse glass for the bangle-makers, use small 



4 F 



