In other words, the boiler with the higher efficiency would weigh two
and a half times that with the lower efficiency. In the case of a vessel
of 3,000 tons, with engines and boilers of 1,500 indicated horse power,
the introduction of locomotive boilers with forced draught would place
at the disposal of the owner 150 tons of cargo space, representing
£1,500 per annum in addition to the present earnings of such a vessel.