Contained within the 3rd Edition (1957) of the Atlas of Canada is a plate that shows two condensed maps of the customs ports handling cargo of 125 000 tons or more circa 1955. Thus, any Canadian port where the Department of National Revenue has a Customs Office. The upper map is concerned with foreign shipping and the lower map is concerned with domestic coastwise shipping. Foreign shipping includes the following: vessels which arrive from a foreign port as last port of call or depart from a foreign port as first port of call; vessels which load cargo for a foreign port or unload cargo from a foreign port; vessels which have other than Canadian or United Kingdom registry, even though they may have arrived at a Canadian port or departed from a Canadian port for another Canadian port. Domestic coastwise shipping includes vessels of Canadian or United Kingdom registry only, which arrive at a Canadian port from another Canadian port or depart from a Canadian port for another Canadian port and do not load freight for a foreign port or unload freight from a foreign port. The full tonnage handled by each port is shown. As well, the ratio of loaded to unloaded cargo is indicated.