in short, that their agency was mechanical. This 
ingenious author of the new system of agriculture 
having observed the excellent effects produced in 
farming, by a minute division of the soil, and the 
pulverisation of it by exposure to dew and air, was 
misled, by carrying his principles too far. Du- 
hamel, in a work printed in 17 54, adopted the 
opinion of Tull, and stated, that by finely dividing 
the soil, any number of crops might be raised in 
succession from the same land. He attempted 
also to prove, by direct experiments, that vegeta- 
bles of every kind were capable of being raised 
without manure. This celebrated horticulturist 
lived, however, sufficiently long to alter his opinion. 
The results of his later and most refined observa- 
tions led him to the conclusion, that no single 
material afforded the food of plants. The gene- 
ral experience of farmers had long before convinced 
the unprejudiced of the truth of the same opinion, 
and that manures were absolutely consumed in 
the process of vegetation. The exhaustion of soils 
by carrying off corn crops from them, and the effects 
of feeding cattle on lands, and of preserving their 
manure, offer familiar illustrations of the principle ; 
and several philosophical inquirers, particularly Has- 
senfratz and Saussure, have shewn by satisfactory 
experiments, that animal and vegetable matters 
deposited in soils are absorbed by plants, and be- 
come a part of their organized matter. But though 
neither water, nor air, nor earth, supplies the 
whole of the food of plants, yet they all operate in 
the process of vegetation. The soil is the labo- 
ratory in which the food is prepared. No manure 
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