31 1 PROCESS FOR 



itfelf, is contracted and cracked, as well as 

 burdened by the aclion of fire, an intermix- 

 lure of land is therefore rcquifitc, \\hich, as it is 

 expanded by heat, and diminifhcs the quantity 

 of the clay, ruull render the whole brick lei's 

 liable to contract. But we mull beware of add- 

 ing too much fund, as that would be unfavour- 

 able to the denfity and folklity of the mafs. 



In making bricks, therefore, as much fund 

 ought to be intermixed as may be nccefl'iry to 

 prevent the bricks from drying and cracking; 

 unlefs particular circumitanccs may recommend 

 a different proportion, of which hereafter. Na- 

 ture, in many places, prefents clay with fuch a 

 Tpixture of faiid, that no addition whatever Is re- 

 cjuifUc. And as it is no cafy tafk to mix clay 

 and fand in the due proportions, that where the 

 mixture has been performed by the hand of na- 

 ture ought always to be preferred. Art cannot 

 imitate the perfection in which nature intermixes 

 thcfe two fub fiances, but produces a rude une- 

 qual mafs, which is variouily affected by the ac- 

 tion of fire, and i* liable to have its deniiry great- 

 ly impaired. Hut when an artificial mixture is 

 fobc made, the (and ought to be chofen fine, and 

 coiiiifling of minute particles rather than thick, 

 and contaminated with earth, and to be painful- 

 ly mixed with the clay. 



The heat mull be fuflicicntly intenfe to melt 

 (the bricks on the furface. This renders them lo 



