48 On the Affinities of 



contained nearly 6-10ths its weight of water, I deemed it 

 necessary to prepare a few experiments with clay dried in a 

 heat of 1 65°, and used almost immediately when taken from 

 the crucible. 



XXXII. Twenty grains of pure clay thus prepared were 

 mixed with l-4th its weight of pure lime, and exposed in 

 a Cornwall clay crucible to 170° of Wedgwood. The re- 

 sult was a partially coagulated mass, slightly adhesive, gra- 

 nulated, and resembling very fine silex. The want of fusion 

 in this experiment arose from the extra quantity of real clay 

 introduced by means of depriving it of its water. 



XXXIII. Twenty grains of the same clay, mixed with 

 10 grains of pure lime, were fused into a transparent glo- 

 bule of glass of a milky white colour. 



XXXIV. This mixture, fused with 1 grain of carbon, 

 yielded a fine glass of a blueish crystal colour. The char- 

 coal was most evidently united in the mass, which exhibited 

 a cloudy water, as if the glass had inclosed a fine charcoal- 

 coloured vapour. This so completely deceived me, that I 

 broke the glass with a view to liberate it, but found it dense 

 and solid throughout. 



XXXV. Twenty grains of pure clay, 10 grains of pure 

 lime, and 2 grains of carbon, were intimately mixed, and 

 fused into a black porcelain mass. The surface was dull 

 and earthy, but the fracture possessed considerable lustre. 

 Half a grain of carbon remained untaken up; so that In- 

 grain had united to the mass in fusion. It may therefore 

 be concluded, that pure clay deprived of all moisture, reck- 

 oning the calcareous earth to have been neutral, absorbs 

 *}\ per cent, of carbon, or betwixt 1 -13th and l-14th part 

 its own weight. 



An abstract of the quantities of carbon united to the dif- 

 ferent substances now operated upon in one fusion, will 

 stand thus : 



Sturbridge clay, vitrified, absorbs of carbon 2-f per cent. 



Cornwall ditto ditto * 4 



Pure clay dried in a heat of 1 65° Wcdg* 7£ 



It is further probable, that were the products thus ob- 

 tained by single fusion reduced and re-fused, with addi- 

 tional doses of carbon, that a still greater combination of 

 carbon would take place, and a greater alteration upon the 

 results ensue. 



I shall conclude this branch of the inquiry with the fol- 

 lowing remarks : 



J st, The combination of carbon with clay uniformly 

 tends to form a black porous porcelain, sometimes resem- 

 bling 



