“ Treasure-trove belongs to the Crown, and in certain districts the right to claim it has been granted to the nobility. In order to come within this rule, the treasure must be concealed, as distinguished from that which is casually lost and remains on the surface, as to which a different rule applies. A finder of treasure-trove is bound by law to give notice of his discovery to the proper officials of the Crown, and his failure to do so may subject him to fine and imprisonment. ”