(2)A ship shall not pay dues both as a home-trade ship and as a foreign-going ship for the same voyage, but a ship trading from a port outside home-trade limits, and discharging cargo or landing passengers or mails at any port within home-trade limits, shall be deemed to be on one voyage as a foreign-going ship, until she has arrived at the last port of discharge of cargo or passengers brought from beyond home-trade limits; and a ship trading to a port outside home-trade limits, and loading cargo or receiving passengers or mails at any port within home trade limits, shall be deemed to be on one voyage as a foreign-going ship from the time she starts from the first port of loading of cargo or passengers destined for a port beyond home-trade limits.