BOOK XVII. IV. 48 VI. 50
sort of marl is used it will injure the soil by its novelty, even with dung it does not promote fertility in the first year. It also makes a difference what sort of soil the marl is required for, as the dry kind is better for a damp soil and the greasy kind for a dry soil, while either sort suits land of medium quality, either chalk-marl or dove-marl. Other manuresV. Farmers north of the Po are so fond of employing ash that they prefer it to dung, and they burn stable dung, which is the lightest kind, in order to get the ash. Nevertheless they do not use both kinds of manure indifferently in the same field, and do not use ashes in plantations of shrubs, nor for some kinds of crops, as we shall explain later. Some are of the opinion that dust helps the growth of grapes, and they sprinkle it on the fruit when it is forming and scatter it on the roots of the vines and the treesa. It is certainly the case that in the Province of Narbonne a wind from west-north-west ripens vintage grapes, and in that district dust contributes more than sunshine.
DungVI. There are several varieties of dung, and its actual employment dates a long way back; as far back as Homer,b an aged king in the poem is found thus enriching his land with his own hands. The invention of this procedure is traditionally ascribed to King Augeas in Greece, and its introduction in Italy to Hercules, though Italy has immortalized Stercutusc son of Faunus on account of this invention. Marcus Varrod gives the first rank to thrushes' droppings from aviaries, which he also extols for fodder of cattle and swine, declaring that no other fodder fattens them more quickly. If our ancestors had such large aviaries that they supplied manure for the fields, it is