There are three kinds of sand: fossil[1] sand, to which one-fourth part of lime should be added;[2] river sand; and sea sand; to both of which last, one third of lime should be added. If, too, one third of the mortar is composed of bruised earthenware, it will be all the better. Fossil sand is found in the districts that lie between the Apennines and the Padus, but not in the parts beyond sea.