HORTUS GRAMINEUS WOBURNENS1S. 129 



Silica, or earth of flint - 50 grains. 



Alumina, or pure matter of clay - 25 



Oxide of iron 4 



Soluble vegetable matter, and sulphate of 

 lime, or gypsum - 4 



The soil was then cropped for five seasons alternately, with 

 1st, oats; 2d, potatoes ; 3d, wheat ; 4th, carrots; and 5th, wheat; 

 to the end that it might suffer as much as could possibly happen, 

 under ordinary circumstances, by an impoverishing or injudicious 

 rotation of annual crops. Every trace of the turf was by this time 

 entirely lost in the general mass of the soil, which was now exa- 

 mined, to ascertain what change it had undergone by these crops. 

 It appeared to consist of 



Calcareous and siliceous sand, nearly as 



before - 100 grains. 



Decomposing vegetable matter, destructible 



by fire - 48 



Carbonate of lime, or chalk, nearly as before 159 

 Silica, or earth of flint - 57 



Alumina, or pure matter of clay - 26 



Oxide of iron 5 



Soluble vegetable and saline matter 3 



The above details shew that very little, if any, change had taken 

 place in the constitution of the soil, in respect of its earthy ingre- 

 dients ; but a very considerable diminution of its decomposing 

 vegetable and animal matters ; particularly when it is considered 

 how great an addition had been made to the original proportion 

 it contained of this constituent, by the turf which was incorpo- 

 rated with the soil. 



The finely divided animal and vegetable matters of soils are so 

 intimately blended with the other constituents, that manure, 

 though applied in sufficient quantity to supply its loss, requires 

 considerable time to bring its parts into that minute state of divi- 

 sion in which it was found in the rich pasture land on the first 

 examination before mentioned. It is evident the finely divided 

 vegetable matter of the pasture land had been supplied to it (as it 

 is indeed to all other pasture lands) by manure successively ap- 

 plied to the surface, either by the cattle which grazed upon it, or 

 by top-dressing, and divided and carried into the soil by the effects 

 of rain. That this essential ingredient of the fertility of soils is 



