Final answer:
The literary device used in 'The snow lay a coverlet over their heads' is personification, which gives the snow human-like qualities of providing comfort and protection, thereby creating a vivid and immersive narrative.
Step-by-step explanation:
In the line "The snow lay a coverlet over their heads," the literary device used is personification. Personification is a figurative language technique where human qualities are given to objects or concepts. The use of this device in the sentence conveys a sense of gentleness and protection, similar to how a coverlet would provide warmth and comfort. It suggests a peaceful, albeit somewhat somber, atmosphere as the snow itself is depicted as taking care to lay itself gently over something, perhaps symbolizing a blanket of snow on the ground or a metaphorical covering over the heads of those beneath it.
Utilizing personification can engage readers by giving them vivid and relatable imagery, allowing for a deeper emotional connection to the scene. It is often employed to enhance the immersive quality of a narrative, making the environment and the action feel more alive and dynamic. In literature, it can serve to highlight thematic elements, in this case possibly touching on themes of nature's overarching presence or the comforting, yet undeniable, power of the natural world.