Overseas Tankship (UK) v Morts Dock and Engineering Co (The Wagon Mound) (1961)

Overseas Tankship (UK) v Morts Dock and Engineering Co (The Wagon Mound) (1961) Facts: Due to the defendants’ negligence, oil was spilled and accumulated  around the claimant’s wharf. The oil ignited and the wharf suffered  fire damage. Held: The defendants were held not liable since, while damage to the  wharf by oil pollution was foreseeable, damage by fire was not. Hughes v Lord Advocate (1963) Facts: The defendant telephone engineers left an inspection hole covered  only by a tent and surrounded by paraffin lamps. A child claimant  was badly injured when he fell down the hole carrying a lamp which  exploded on impact causing a fireball. Held: The defendants were liable as they should reasonably have  foreseen that a child would be attracted by the lamps and might be  burned when playing with them. It was irrelevant that they could not  have foreseen the explosion or the severity of the burn damage. Sir in the above 2 scenerios, I did not understand that why defendant was not liable in wagon mound case, and why defendant was liable in Hughes V Lord advocate case?