56 Tloe Principles of Part II. 



i 



THE fame quantity of ftone marl, treat- 

 ed the fame way, afforded juft the fame 

 proportion of clay and calcarious earth. 



MARL, then, is a body compofed of lime 

 and clay in different proportions, according 

 to the different kinds of marl, and generally 

 about one fourth of lime and three fourths 

 of .clay. 



FROM this experiment we may eaiily 

 account why marl falls in water, as lime 

 ftrongly attracts water -, and why it lofes 

 this property when burnt, as clay becomes 

 more tenacious by fire ; why it cannot be 

 converted to brick, as the lime hinders that 

 clofe adhefion of the particles of clay which 

 is neceiTary to conftitute brick ; why it will 

 not vitrify, as lime is an enemy to all vitrifi- 

 cation j and why it mews a fmall portion 

 of oleaginous matter, as clay contains fome 

 oil. By mixing quick or rather effete lime 

 with clay, or a clay foil, we imitate, in 



fome 



