The great bulk of the foreign trade of this country is sea-borne, and the traffic by air and land, though important in many ways, is comparatively small in volume. It seems best, therefore, to describe the Customs administration of imports and exports by ship, and then show how this has been adapted to air and land traffic. Within the limits of such ports the Commissioners of Customs and Excise may appoint boarding-stations for ships to bring to in order that Customs officers may board or be landed from them. The law provides that bulk must not be broken before report, unless the Commissioners of Customs and Excise have given their prior authority either specifically or by a general authorization. The exports require the same kind of documents as for sea traffic, and goods are examined for drawback, or the discharge of a bond, at the Customs station.