Causes of Fertility or Barrenness of Soils. 193 
We proceed to j2^ive the analysis of a few soils of various kinds, 
commencing: with that of a clay soil, from the upper oolite forma- 
tion, near Cirencester, by Dr. Voelcker : — 
Water driven off at 212^ 5"53 
Insoluble Matter (Clay) 84-10 
Oxides of Iron and Alumina Sol 3'07 
Organic Matter and Water of Combination .. .. 3-62 
Carbonate of Lime '74 
Magnesia '60 
Potash -26 
Soda -22 
Phosphoric Acid '38 
Soluble Silica 1-45 
99-97 
In this analysis we are struck with the very minute quantity of 
the soluble in proportion to the insoluble matters, and might 
hastily judge such a soil to be very sterile, an erroneous conclu- 
sion, of which we shall at once be convinced if we bear in mind 
the very minute quantity required for each crop. Professor Way, 
who has paid great attention to this subject, informs us that the 
total weight of soil removed from an acre of ground by an average 
wheat crop only amounts to 277 lbs. ; twenty crops taking 
5540 lbs., or '248 per cent, of the whole soil. He gives the fol- 
lowing tables : — 
1 Crop. 
20 Crops. 
Percentage 
of Soil 
removed 
by 2U Crops. 
Silica 
Phosphoric Acid 
Lime 
Magnesia 
Potash 
lbs. 
170 
30 
8 
16 
10 
40 
3 
lbs. 
3400 
600 
160 
320 
200 
800 
60 
•152 
•027 
•007 
•014 
•009 
•036 
•003 
277 
5540 
•248 
The following is the analysis of a calcareous soil from Glouces- 
tershire : — 
Lime 52-33 
Magnesia '31 
O.xidc of Iron and Alumina 2 '86 
Phosphoric Acid Trace 
Sulphuric Acid Trace 
Silica -26 
Carbonic Acid 44*70 
100-46 
VOL. XVI. O 
