The long ton is used for petroleum products such as aviation fuel. Deadweight ton (abbreviation 'DWT' or 'dwt') is a measure of a ship's carrying capacity, including bunker oil, fresh water, ballast water, crew and provisions. It is expressed in tonnes (1000 kg) or long tons (2240 pounds, about 1016 kg).
Trains between Naples and Sorrento depart once every half hour and take about 55 to 68 minutes in duration. Thus, to get from Rome to Sorrento, you would first take a train to Naples, where you would switch to a Circumvesuviana train down to Sorrento.
Trains take about 90 minutes to complete the trip, which is by far the fastest way to go, taking into account traveling to airports, security and check-ins for flights. Florence-bound trains leave from all Rome train stations, which will be indicated with the phrase Tutte Le Stazioni on your timetable.