So wrote Fairbairn in 1861. He had good reason to value the importance of boilers. He had built many steam engines and carried out experiments to improve their efficiency. He had also experimented with different types of boilers and tried various ways of burning coal in their furnaces as efficiently as possible, with the result that he developed the ‘Lancashire’ boiler, which was the most usual type in cotton mills from roughly the 1850s until the final abandonment of steam power.

Yet boilers have been too often the forgotten and most neglected parts of steam engines, with sometimes literally fatal results. This was because most people lacked even a basic understanding about how they should function. First, it was necessary to learn about the nature of coal and the different properties of the various types. Then the furnace had to be designed to burn the particular coal in the best way.