SUPPLEMENTARY DISSERTATION 
O N 
ft * 
SOIL S, MANURES, &c. 
Q OILS, in general, are found to con- 
^ fill of the following fubftances, viz . 
Clay, 
Sand, 
Gravel or Hones, 
Calcareous and abforbent earths, 
Vegetable fubftances, containing oil. 
Metallic fubftances, and 
/ 
Salts. 
Clay is a foft fine powder, on the ap¬ 
plication of water it becomes tenacious, 
and 
