Caveman metaphor
Allie uses a metaphor to describe Askew, saying "He's a caveman." This metaphor associates Askew with a key theme in the book, which is the ancient past. This description also foreshadows that Askew will be the inspiration for Kit's story about a caveman called Lak.
Silky simile
Kit's grandfather describes Silky using a simile: "Called him that cos of the way the lamplight fell on him. Cos it made him shine like flickering silk as he flashed through the tunnels before our eyes." This description emphasizes the lightness of Silky, suggesting he is a ghost.
The ammonite simile
Kit's grandfather is describing the ammonite, and says that a small creature lived inside it, "like a snail does, or a hermit crab." By comparing the creature of the ammonite to an animal Kit is aware of, Kit's Grandfather effectively teaches Kit about the ammonite.
Mine metaphor
During a conversation about history, Kit's grandfather says that when the miners dropped down the mine, they "dropped through time. Million years a minute." This metaphor represents presence of the past all around us, and how his grandfather was deeply connected to the past when he was mining.
