$S The Principles of Part II. 



THOSE who have been much ufed to 

 marl, have already difcovered a difference 

 betwixt it and this body. The former, 

 they obferve, takes a fmooth polifh from 

 the inftruments with which it is wrought, 

 but the latter does not. As this quality 

 alone is fcarcely fufficient to diftinguim thefe 

 two bodies from one another, let us apply 

 to experiment for more. 



Exp. 25. If a piece of ijt is taken up 

 which has not been much expofed to the 

 influence of the air, it differs very much 

 in tafte from marl. Inftead of the fmooth 

 unctuous tafte of the latter, it is acid, and 

 remarkably aftringent. 



IT agrees with marl in falling down into 

 a powder in water ; but then it differs re- 

 markably from it, in raifing no affervefcence 

 with acids, nor in the leaft deftroying their 

 acidity. 



IT 



