Steam Boilers, Engines, Nozzles and Turbines
The difference between Cornish boiler and Lancashire boiler is that

Former contains one fire tube and latter contains two fire tubes
None of the listed here
Former is water tube type and latter is fire tube type
Former is fire tube type and latter is water tube type boiler

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Steam Boilers, Engines, Nozzles and Turbines
The object of producing draught in a boiler is

To provide an adequate supply of air for the fuel combustion
To discharge the gases of combustion to the atmosphere through the chimney
All of the listed here
To exhaust the gases of combustion from the combustion chamber

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