In March, 1837, Van Buren became President, and found it necessary to take some action. The documents bearing on our claims were critically examined; fifty-seven cases, apparently free from doubt, were made out and proved; and in July, Robert Greenhow, interpreter of the state department, presented them at Mexico with a final demand for redress, adding that we had no desire to cause embarrassment by pressing for payment. On one point, however, he insisted: Gorostiza's conduct must be disavowed. The minister of relations admitted in reply that certain of the cases did not require long examination, which was indeed true; but he said the President, while "most anxious" not to cause delay, wished that "each" of them should be examined "in its turn" and that "nothing should be left undone" which could promote "the most speedy and equitable" settlement.[3.34] In November Martínez, a new minister to the United States, whom we received kindly even though Gorostiza's action had not been disavowed, presented the answer of his government. Instead of the document officially transmitted by Greenhow, an obsolete, incomplete and necessarily inaccurate list of our claims, obtained nobody knows how, had been used; only four of our fifty-seven living cases had even been considered; and not one of these had been disposed of. Accordingly, when our Congress assembled in December, 1837, the Executive laid the whole subject before it anew, analyzed Mexico's evasive reply--so different from what had been solemnly promised--announced that fresh outrages of a serious and exasperating sort had been committed, and plainly intimated that no hope of a peaceful settlement could be entertained. Evidently the patience of the United States had nearly come to an end; but before Congress was ready to act, Martínez proposed a scheme of arbitration, which--though formally decided upon by Mexico in May, 1837--it had apparently been her deliberate purpose to hold in reserve until all other dilatory tactics should have been exhausted.[3.35] [ARBITRATION AGREED UPON] Naturally our government hesitated to adopt a plan which, as the British representative at Mexico wrote when he heard of it, was precisely the one to "gratify the favourite object" of our debtors--"the gaining of time and postponement of the day of reckoning"; but in April, 1838, quite unlike France and much to the surprise of Mexico, we accepted arbitration, and it then appeared that Martínez had no powers to act in the matter. For months, indeed, although our consul at Mexico was assuring that government of our fair and friendly disposition, he did not receive them.[3.36]