[ 180 ] 



A specimen of good soil from Tiviot-dale, afford- 

 ed five sixths of fine siliceous sand, and one sixth of 

 impalpable matter ; which consisted of 



41 Alumina, 



42 Silica, 



4 Carbonate of lime, 



5 Oxide of iron, 



8 Vegetable, animal, and saline matter. 

 A soil yielding excellent pasture from tne valley 

 of the Avon, near Salisbury, afforded one eleventh of 

 coarse siliceous sand j and the finely divided matter 

 consisted of 



7 Alumina, 

 14 Silica, 



63 Carbonate of lime, 

 2 Oxide of iron, 



14 Vegetable, animal, and saline matter* 

 In all these instances the fertility seems to de- 

 pend upon the state of division, and mixture of the 

 earthy materials and the vegetable and animal matter ; 

 and may be easily explained on the principles which I 

 have endeavoured to elucidate in the preceding part 

 of this Lecture. 



In ascertaining the composition of sterile soils 

 with a view to their improvement, any particular 

 ingredient which is the cause of their unproduc- 

 tiveness, should be particularly attended to ; if possi- 

 ble, they should be compared with fertile soils in the 

 same neighbourhood, and in similar situations, as the 

 difference of the composition may, in many cases, in- 

 dicate the most proper methods of improvement. If 



