3 86 PROCESS FOR 



and hence we haver indications by which we nr 

 diltmguifh when bricks ;rrc thoroughly burnt in 

 the kiln. Every pcrfon is ready to obferve that 

 brick? are too foft, and imperfectly burnt : but 

 few have (kill enough to difcern the blunders 

 whicli are liable to be committed in the proceiV 

 of preparing bricks, or how far t!ie burning 

 ought to be carried. For tlh: apyrous clay or" 

 which bricks are fumetimcs computed is not vi- 

 triliuble merely by burning: and indeed no vi- 

 triiication is neceilary when they can be render- 

 ed hard enough iblely by the violent aclion of 

 fire, If, however, a vitreous cruJl be thought ne- 

 ceiftry, it may be formed v/ith great eufo, and 

 almoit no expence, by liitfvinUhing the fire for a 

 little, throwing in a fmall quantity of fait, and 

 ilmttiiu 1 ; up the kiln immediately. The bricks 

 v. ill thus infallibly acquire u vitreous crufl, and 

 That in the reudieil manner poilible. It only re- 

 mains to determine the |>roportion of f.ilt necef- 

 lary. 



j 



> 5 x. Method ofaffliyin^ Ckiyfor.Tik.r. 



To infurc fuccefs, it will be highly proper to 

 examine the nature of the clay before proceeding 

 to form it into bricks. This may be moll expe- 

 diltoufly done in the following manner: nitrous 

 ;n:il. p ->urcii upon un burnt clay, dete^U the pre- 



fence, 



