9* A SYS T E U O F 



SECT. LXXXIV- 



Jt Stone Marrow, Lithomarga : Keffiiil of the 



Tartars. 



I have given this name to a kind of clay, 

 which, 

 i. When dry, is as fat and fiippery as 



foap : but, 



2. Is not wholly diffufible in water, in which 

 it only falls to pieces, either in larger bits* 

 or reiembles a curd-like mafs. 



3. In the lire it eafily melts to a white or 

 reddiih frothy flag, therefore confequently 

 is of a larger volume than the clay was 

 before being fufed. 



4. It breaks into irregular Italy pieces. 



A. Of coarie particles : Coarfe Stone Mar- 

 row. 



£i. Grey, from Ofmundfberget, in the 

 parilh of Rettwik, in Dalarne, and 

 is there called walklera^ that is, fuller's 

 earth. It is mentioned in an account 

 of Ofmundfberget, publifhed in the 

 Tranfactions of the Academy of 

 Sciences at Stockholm, in the year 

 1739, by the Berg's-radet, or mine- 

 mafter, Mr Tilas . 

 h. Whitifh yellow, from the Crim 

 Tartary, where it is called Keffekil, 



it is anfwered, That they are found together in the fame beds 

 svhh the porcelain clay : that they have all the fame ex- 

 ternal rgns, and differ from it only in the colour, being red, 

 brown, or black, in regard to the contained metal : that 

 they are more refractory in the fire than any other martial 

 clay ; and that, though they may be reduced fo as to refemble 

 a black cr irofc -coloured flag, they yc: retain their form. 



and 



