C 158 ] 



III. TERRM. 



50. OcHRA. Ochres. Earth: precipitated caljc 



or earth of metals. 

 Particles: coloured, and 

 extremely minute. 



51. Arena. Sand. Earth: originated from wa- 



ter* 



Particles: diftinft, granu- 

 lated, hard, and fca- 

 brous : neither pene-^ 

 trable nor congluti- 

 nable by water. (Not 

 foluble in acids.) 



52. Argilla. Clay. Earth : originated from the 



vifcid fediment, or mud, 

 of the fea. 



Particles : irregular, im- 

 palpable, foftj tough, 

 and lubricous. 



In water : becoming foft, 

 undluous, and plaftic. 



In the fire : hardening. 



53. Calx. Chalks. Earth : of animal origin. 



Particles : dry, farinace- 

 ous, friable, colouring 

 the fingers : tinging 

 water: moftly foluble 

 in acids, and effervef- 

 cing therein, efpecially 

 when calcined or burn- 

 ed. 



54. Humus. 



