Should reasonable care protect against all conceivable harm, no matter how unlikely? Defendant operated a trolley line, using an overhead wire system to supply power to the trolleys. Plaintiff—a young boy—ran across a bridge while swinging an eight-foot wire of his own. The defendant’s trolley wire ran beneath the edge of the bridge. In swinging his wire, the plaintiff’s wire made contact with defendant’s trolley wire, shocking and burning the plaintiff.