This affront to Spanish pride might have ended abruptly a chapter in Spanish-American diplomacy but for the friendly offices of Hyde de Neuville, the French Minister at Washington, whose Government could not view without alarm the possibility of a rupture between the two countries. It was Neuville who labored through the summer months of this year, first with Adams, then with De Onis, tempering the demands of the one and placating the pride of the other, but never allowing intercourse to drop. Adams was right, and both Neuville and De Onis knew it; the only way to settle outstanding differences was to cede these Spanish derelicts in the New World to the United States.
To bring and keep together these two antithetical personalities, representatives of two opposing political systems, was no small achievement. What De Onis thought of his stubborn opponent may be surmised; what the American thought of the Spaniard need not be left to conjecture. In the pages of his diary Adams painted the portrait of his adversary as he saw him--"cold, calculating, wily, always commanding his temper, proud because he is a Spaniard but supple and cunning, accommodating the tone of his pretensions precisely to the degree of endurance of his opponents, bold and overbearing to the utmost extent to which it is tolerated, careless of what he asserts or how grossly it is proved to be unfounded."
The history of the negotiations running through the fall and winter is a succession of propositions and counter-propositions, made formally by the chief participants or tentatively and informally through Neuville. The western boundary of the Louisiana purchase was the chief obstacle to agreement. Each sparred for an advantage; each made extreme claims; and each was persuaded to yield a little here and a little there, slowly narrowing the bounds of the disputed territory. More than once the President and the Cabinet believed that the last concession had been extorted and were prepared to yield on other matters. When the President was prepared, for example, to accept the hundredth meridian and the forty-third parallel, Adams insisted on demanding the one hundred and second and the forty-second; and "after a long and violent struggle," wrote Adams, "he [De Onis]. .. agreed to take longitude one hundred from the Red River to the Arkansas, and latitude forty-two from the source of the Arkansas to the South Sea." This was a momentous decision, for the United States acquired thus whatever claim Spain had to the northwest coast but sacrificed its claim to Texas for the possession of the Floridas.