To provide for the accommodation of the recruits to his army of agriculture, the King applied every art of government to bring new land under cultivation and to increase the fertility of the old. The superior enlightenment of Prussia was attested by the curt refusal of Brunswick and Hanover to co-operate in works of drainage. No site for a farmstead was to be left vacant and in the forests—so ran the decree—“no place where a tree can stand, unplanted.” The sterile nature of the soil challenged the unwearied industry of the King. Many centuries before blotting-paper came to be known, Brandenburg was nicknamed “the sand-box of the Holy Roman Empire.” Thousands of acres had to be set with bushes to prevent its surface from being blown over the neighbouring fields. “I confess,” wrote Frederick to Voltaire, “that with the exception of Libya few states can boast that they equal us in the matter of sand. Yet we are bringing 76,000 acres under cultivation this year as pasture. This pasture feeds 7,000 cows, whose dung will manure and improve the land, and the crops will be of more value.” The spectacle of the royal philosopher writing to Voltaire about manure and walking almost daily from Sans Souci to his turnip-field is a visible proof of Frederick’s devotion to this branch of his stewardship. He was wont to speak with authority as the leading agriculturist of the realm. Here, as elsewhere, his breadth of view often enabled him to discern the best product or practice in other lands, and his command of resources to transport it to his own. Having once attained his object by teaching his subjects to produce an article at home, he imperatively forbade them to import it from abroad. The full reward of his policy would be reaped when Prussia began to supply it to other countries in exchange for gold and silver. A single instance of the minuteness and imperiousness with which the King applied this policy to agriculture may be cited from Professor Koser’s history of the reign. The Berlin egg-market was still dependent on foreign supply. In 1780 a royal hen-census showed that there were 324,175 hens in the Electoral Mark and that 36,300 more were required to meet the demand for eggs. “What will it matter,” asked the King, “if every peasant keep ten or twelve more hens? Their food does not cost much; they can pick up most of it in the straw and dung of the farmyard.” Prohibition of the import of foreign eggs followed. This caused the market price to rise and the ministers expressed the fear that the supply would not be sufficient. The King rejoined: “It is all the fault of the farmers and peasants for not setting about it. I have laboured forty years to introduce things of this kind. If the ministers want to eat eggs, let them take more trouble with the Chambers to carry it through. The prohibition of foreign eggs remains as before.”