If two or more causes concur to bring about an event, then the cause-in-fact of an injury is established by the “substantial factor”ť test. The court applied the “substantial factor”ť test imported from the rule in the Cook case, 98 Wis. 624, 74 N.W. 561, 40 L.R.A. 457, 68 Am. St. Rep. 830, which exempted Defendant from liability since there were other fires sweeping east towards Plaintiff’s property, and any one of those fires could have been the actual cause of Plaintiff’s loss. The narrow rule in this case states that if a fire combines with another of no responsible origin, and after the union of the two fires, they destroy the property, and either fire independently of the other would have destroyed it, then, irrespective of whether the first fire was or was not a material factor in the destruction of the property, there is no liability.