"[I]f we put aside those gardeners who chiefly cultivate the... primeurs—strawberries ripened in January, and the like—if we take only those who grow crops in the open field, and resort to frames exclusively for the earlier days of the life of the plant and if we analyse their system, we see that its very essence is first, to create for the plant a nutritive and porous soil, which contains both the necessary decaying organic matter and the inorganic compounds; and then to keep that soil and the surrounding atmosphere at a temperature and moisture superior to those of the open air. The whole system is summed up in these few words. If the French maraîcher spends prodigies of labour, intelligence, and imagination in combining different kinds of manure so as to make them ferment at a given speed, he does so for no purpose but the above: a nourishing soil and a desired equal temperature of the air and the soil. All of his empirical art is devoted to the achievement of these two aims. But... the soil can be improved by hand, but it need not be made by hand. Any soil... can be made by machinery. ...[W]e shall see manufactures of as soon as there is a demand for them."