Manures purchased annually in England.
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Prof. Anderson gives the following estimate of the amount expended annually by the farmers of
Great Britain for artificial manures:
| Guano | $12,500,000 |
| Nitrate of Soda | 1,125,000 |
| Bones | 1,200,000 |
| Super phosphates | 2,100,000 |
| Coprolites | 1,875,000 |
| Sulphate of Ammonia | 750,000 |
| Other Articles | 500,000 |
| Total | $20,950,000 |
This expenditure, coupled with improved methods of tillage, accounts for the fact that the average product of wheat in
England has been raised from 8 or 9 bushels to nearly 30 bushels per acre.
