But while a general magical efficacy may be supposed to reside in all stones by reason of their common properties of weight and solidity, special magical virtues are attributed to particular stones, or kinds of stone, in accordance with their individual or specific qualities of shape and colour. For example, the Indians of Peru employed certain stones for the increase of maize, others for the increase of potatoes, and others again for the increase of cattle. The stones used to make maize grow were fashioned in the likeness of cobs of maize, and the stones destined to multiply cattle had the shape of sheep. In some parts of Melanesia a like belief prevails that certain sacred stones are endowed with miraculous powers which correspond in their nature to the shape of the stone. Thus a piece of water-worn coral on the beach often bears a surprising likeness to a bread-fruit. Hence in the Banks Islands a man who finds such a coral will lay it at the root of one of his bread-fruit trees in the expectation that it will make the tree bear well. If the result answers his expectation, he will then, for a proper remuneration, take stones of less-marked character from other men and let them lie near his, in order to imbue them with the magic virtue which resides in it. Similarly, a stone with little discs upon it is good to bring in money; and if a man found a large stone with a number of small ones under it, like a sow among her litter, he was sure that to offer money upon it would bring him pigs. In these and similar cases the Melanesians ascribe the marvellous power, not to the stone itself, but to its indwelling spirit; and sometimes, as we have just seen, a man endeavours to propitiate the spirit by laying down offerings on the stone. But the conception of spirits that must be propitiated lies outside the sphere of magic, and within that of religion. Where such a conception is found, as here, in conjunction with purely magical ideas and practices, the latter may generally be assumed to be the original stock on which the religious conception has been at some later time engrafted. For there are strong grounds for thinking that, in the evolution of thought, magic has preceded religion. But to this point we shall return presently.