DOMAIN III. ARGILLACEOUS. 



Saussure, 1944, describes a kind of clay rock 

 found among the pebbles of the two rivers called 

 Emme, in Swisserland. This substance having 

 hitherto little engaged the attention of mineral- 

 ogists or geologists, all the accounts are very 

 imperfect, 

 porcelain Porcelain clay sometimes constitutes rocks; 



clay. 



but it is merely a decomposed felspar, which 

 may be found in the Domain entitled Decom- 

 posed Rocks. Potters' clay seems only to occur 

 in separate strata ; when of a greyish white, it 

 is called pipe-clay. The clay of which the 

 famous Egyptian vases have been formed for 

 many thousand years, is, according to Roziere, 

 of a marly nature, and is found near Coptos in 

 the Thebaid. It approaches to the fawn co- 

 lour, and is of a porous and light consistence. 

 Porous vases which, by evaporation, impart 

 great coolness to water, are also made in Spanish 

 America, where the ladies are even fond of eat- 

 ing the fragments*. Molina, in his interesting 

 account of Chili, has described several valuable 

 clays, of which there is one which long retains a 

 sweet smell. 

 Boies. The Lemnian, Armenian, and other boles, 



* Da Costa, p. 20, says it is a bole useful in acidities, and as a 

 dentifrice. 



