Edmund’s Torch was an electric one, given to Edmund as a birthday present in England, just one week before he was transported to Narnia, with his brother and sisters, for the second time, to help Prince Caspian. He used the torch as a light for him and his siblings when they went down to explore the Treasure Room of Cair Paravel. Apparently, when Edmund returned home to Earth, he had forgotten to retrieve his torch, and left it behind in Narnia. In the movies, the torch is used a lot more extensively.