Final answer:
The quote describes the employment circumstances of factory workers in industrial mills during the industrial revolution.
Step-by-step explanation:
The quote describes the harsh and grueling conditions of factory workers during the industrial revolution. The vivid imagery of 'pale, lean men' in 'faded garments,' the 'roar' and 'thunder' akin to 'a hundred lions' and 'cannons', alongside the 'jangling clang of falling iron,' all suggest an industrial setting where workers had to endure the extreme heat and noise associated with massive industrial machinery. This description is indicative of the difficult employment circumstances faced by workers in industrial factories, particularly in mills where iron was processed.