What must a farmer know in order to avoid failures? Can this be learned entirely from observation? What kind of action have manures? Give examples of each of these. May mechanical effects be produced by chemical action? How does potash affect the soil? To understand the science of manures is the most important branch of practical farming. No baker would be called a good practical baker who kept his flour exposed to the sun and rain. No shoemaker would be called a good practical shoemaker, who used morocco for the soles of his shoes, and heavy leather for the uppers. No carpenter.
