The Congress of the United States passed a "Neutrality Bill" which cleared up the situation a great deal by denying official sanction to any schemes of invasion and enjoining neutrality on all American citizens. The state authorities along the frontier also tried to prevent any movement of armed forces against Canada. Theller records how he successfully dodged the American authorities in making his attack on Fort Madden and how Governor Mason of Michigan was coming down the river with a strong force when Theller and his friends approached the island of Bois Blanc which lies in Canadian waters. No doubt there often was a certain amount of laxity on the part of the American authorities, and Sir George Arthur finds occasion to condemn it at times, but the United States Government seems on the whole to have acted very wisely. The burning of the "Caroline," which it should be remembered was an American vessel attacked by a Canadian force in American waters, might easily have led to very serious consequences. If President Van Buren and his cabinet had wanted war it would have been quite possible to claim the destruction of the ill-fated "Caroline" as an overt act of hostility. Fortunately milder counsels prevailed and war was avoided. But this incident profoundly affected and prolonged the agitation on the American side of the border. On April 23rd, 1838, an "authorized agent" of the United States Government, Mr. Aaron Vail, who had recently been Chargé d'Affaires in the American Embassy in London, arrived at Toronto. Mr. Vail, according to the official despatch of the British ambassador at Washington, Mr. H. S. Fox, was charged with the task "of inquiring into, and reporting upon, the actual condition of various individuals, who are now in confinement in Canada." Mr. Fox considered Mr. Vail a very fitting envoy and that his mission would be beneficial "by dissipating false rumours which tend to keep alive feelings of ill-will between the British and American inhabitants on the Canadian frontier."