BURNING BRICKS. 387 



fence of lime by producing an effervefcencc. 

 Calcareous clays, or marie of this character arc 

 ofrcn the littc.l materials for bricks. Farther, 

 take a lump of cl.iv, of a given weight; mace- 

 rate it in water, and flrakc the mixture; then, 

 fullering the heavier parts to iink to the bottom, 

 pour the liquid into a different vcfiel; mix the 

 refiduc with anew quantity of water, and repeat 

 this proccfs, till the whole become perfectly 

 limpid. The clay is now all diifulved, and 

 what remains is nothing but fancl. What- 

 ever matter may be found to have fubfided in 

 ihc different vclll-ls, may alib be reduced by re- 

 peated wafhings to the fmell (and. Again, to 

 fe para te the lime which may be intermixed with 

 the clay, pour upon a quantity of clay in any 

 vcflcl fpirit of nitre to the depth oi'a few inches; 

 ditrcft the fpirit of nitre upon the clay, then after 

 the eilcrvefcencc has ceafed, let the clear liquor 

 be poured on the land previoufly fcparated, which 

 is fomctimes equally contaminated with lime. An 

 additional portion of clay mult be from time to 

 time added to the aquafortis, till the cflervef-. 

 cence entirely ceafe. The clay and fand arc 

 then taken hot, and wafiied apart. It is ncedleis 

 to burn the clay in thefe experiments, ai 

 that would diiVolve a part of it. But, let fpirit 

 t>f volatile alkali be dropped into the folutkm of 

 lime in nitrous acid, till the lime be precipitated; 

 pour the pure liquor into a different vcflcl; and 

 B b 2 \vafli 



