Final answer:
The author uses symbolism by comparing shadows to 'black swords,' implying a conflict between the characters, creating an underlying sense of tension or struggle.
Step-by-step explanation:
In the provided line, "In lamplight, and over the flames of the cooking stove, their two shadows clashed and crossed on the ceiling like black swords," the author uses symbolism to convey a sense of conflict or tension between the two figures without explicitly stating it. The comparison of the shadows to "black swords" symbolically suggests a battle or fight, hinting at an underlying struggle or clash of wills, interests, or personalities. This technique is an example of how authors often use elements like shadows and light to represent abstract concepts and evoke emotions or ideas beyond the literal scenario.