102 A S Y S T E M O F 



The ufe of clays, in common life, is more ex- 

 tenfive than I have been able to inform my felt 

 of-, for which reafon I will only mention ibme 

 particulars relating to it. 



The porcelane clay is employed to make vef- 

 fels which have that quality already mentioned 

 (Seel. lxxviiL). I make no doubt but it enters into 

 the compofition for making the fine porcelane 

 ware at fome places ; at leatt veffels are prepared 

 from it of the fame goodnefs in every refpect : 

 and there are likewife fome varieties of this clay* 

 which become quite white in the fire, a quality 

 which is efteemed the moll valuable in the fine 

 China ware. 



The indurated porcelane clay cannot be eafily 

 heated without cracking, and is therefore of no 

 great fervice, if hardened in the fire alone, and in 

 its natural ftate : though this circumftance is of 

 lefs inconveniency, than when it has original 

 cracks, or is mixed with heterogeneous fubflances. 

 The ileatites * is found purer and more folid in 

 China than in any place in Europe. The natural 

 faults of the European ones may, however, be 

 altered by adding fome fat fubflance to it, when it 

 is to be burnt ; by which means it becomes black 

 or brown ; and this method is faid to be ufed at 

 Bareith. The coarfe porcelane-like earth, which 

 goes by the name of French clay, is ufed at the 

 glafs-houfes, Heel furnaces, and other works of 

 the fame nature, for the fame reafons as it is the 



* The fteatites here meant is the fubftance of w^ich the 

 Chinefe jofles or figures commonly called rice figures are 

 made : it is, according to my method, of the clafs of Talcs, 

 and of the genus of Nephritics. D. C. 



principal 



