In the second trial, Mexico advanced a wholly different theory from that developed in the diplomatic discussions between the first and second trials. Mexico now maintained that the boundary treaties of 1848 and 1853 had laid down a "fixed line" between the two countries in the centers of the channel of the river as surveyed at that time by Commissioners Emory and Salazar, which boundary line remained immutable irrespective of any subsequent change in the course of the river, whether erosive or avulsive, until this was changed for the future by the treaty of 1884. Mexico contended this latter treaty was not retroactive but applied only to river changes taking place after 1884. Driven to concede that in this view the treaty of 1884 had really no meaning, Mexico insisted the two governments were under a misapprehension when this treaty was negotiated, that it was inoperative and that the general rules of international law governing river boundaries had no application because the Rio Grande was in a technically legal sense not a river at all, but merely an intermittent torrential stream. The United States denied that the boundary treaties of 1848 and 1853 established a fixed line, and contended the treaty of 1884 was retroactive in any event, and applied to the Chamizal dispute, and that this treaty was merely declaratory of the general rule of international law. Furthermore, the United States claimed the Chamizal tract by prescription. The case was argued during sessions of the Commission extending over a month. The presiding Commissioner, Mr. Lafleur, rendered an opinion holding squarely against the Mexican contentions with respect to a fixed line and the non-retroactivity and non-applicability of the treaty of 1884. His discussion of these subjects is detailed and masterly. After holding against the American claim based on prescription, he appeared to assume that the treaty of 1884 contemplated some _tertium quid_ aside from erosion and avulsion, which might perhaps be called "violent" erosion and which had the same effect as an avulsive change, namely, to leave the boundary line in the abandoned bed of the river. Applying this latter doctrine he found the erosion at the Chamizal tract from 1852 to 1864 had been gradual within the meaning of the treaty of 1884, and therefore the boundary during this period had followed the river, but that the floods of 1863 brought about a violent erosion, whereby the boundary line was left in the middle of the bed of the river "as it existed before the flood of 1863." He therefore awarded that portion of the tract between the channel of 1852 and the channel of 1864 before the flood, to the United States, and the remainder to Mexico.