Difference between Cornish and Lancashire boilers Which statement correctly differentiates the Cornish boiler from the Lancashire boiler with respect to the number of main flue tubes?

Introduction / Context:
Both Cornish and Lancashire boilers are classic internally fired, fire-tube, shell boilers used historically for low to medium pressures. Examinations often ask for the simplest, most memorable differentiator: the number of main furnace flue tubes running through the shell.

Given Data / Assumptions:

• Internally fired fire-tube construction for both types.
• Single- versus twin-furnace arrangements influence heating surface and capacity.
• Operating at similar pressure ranges in older installations.

Concept / Approach:
The Cornish boiler has a single large flue tube that houses the furnace and carries hot gases to the back end before returning via smaller flues. The Lancashire boiler, an evolution of the Cornish, uses two parallel furnace flue tubes within the same shell, increasing grate area and heating surface, thereby improving steaming capacity.

Step-by-Step Solution:
Identify Cornish: one main furnace tube.Identify Lancashire: two main furnace tubes.Match to the answer stating “one” versus “two.”Conclude option (c) is correct.

Verification / Alternative check:
Standard boiler diagrams clearly depict one large furnace tube in Cornish and two in Lancashire shells.

Why Other Options Are Wrong:
Options (a) and (b) misclassify the boiler type; (d) reverses the counts; (e) is incorrect because both are fire-tube, not water-tube.

Common Pitfalls:
Confusing multi-pass gas paths with the number of main furnace tubes.

Final Answer:
Cornish boiler has one flue tube whereas Lancashire boiler has two flue tubes.