This is Ignis fatuus, or “foolish fire.” It is the name given to fire obtained by rubbing two pieces of wood together, and is used in superstitious ways. Amongst the Russian peasantry it is believed that these wandering lights are souls of still-born children, who do not desire to lure people from the path, but who get no rest till they find their bodies. A.G.H.

Source: 81, 139.