In most English accounts it is taken for granted that Louis Philippe selected the Duke of Cadiz as a husband for Isabella, in order to make certain that the succession to the Spanish throne should pass to the descendants of Montpensier. But the circumstances do not warrant this assumption. Count Trapani, whose physical fitness was never called into question, was always his favourite candidate. It was only in the last resort, when, owing to the unpopularity of the Neapolitan connection, he was forced to bring forward another Bourbon, that he fell back upon Cadiz. The suspicions which existed about the virility of this young prince did not deter the King from seeking to impose him upon Isabella. He cannot, however, be fairly charged with having expressly chosen him, because he believed him to be impotent. Don Enrique and the sons of Don Carlos being for different political reasons out of the question, he had no option but to renounce his Bourbon principle, or to insist upon the Queen's marriage with the Duke of Cadiz. The experience of England during the eighteenth century had taught her to look with dread upon the prospect of having to struggle single-handed against the two Bourbon Powers. The lesson of 1783 was never forgotten by her statesmen. Under the Restoration, when the absolute rule of Ferdinand VII. was re-established by French bayonets, Mr. Canning, to avert the dangers of a close alliance between the Courts of Madrid and of the Tuileries, acknowledged the revolted Spanish colonies and "called in the new world to redress the balance of the old." Palmerston was confronted by a different situation. Spain was weaker, but France had acquired Algiers and was upon terms of suspicious friendliness with Mehemet Ali. In alliance with the Pasha of Egypt in the east and with Spain in the west, she might, it was to be feared, obtain a complete control of the Mediterranean. It was, therefore, Palmerston conceived, a matter of the first importance that her influence over the Cabinet of Madrid should be destroyed. This object, in his opinion, could never be successfully attained until Spain should be endowed with Liberal institutions, and should adopt a national, not a dynastic, policy. It was with this end in view that he entered into the Quadruple Treaty, by which England engaged to assist the _Christinos_ to expel Don Carlos from the Peninsula. Without doubt, the idea upon which his policy was based was statesmanlike; nevertheless, the methods by which he hoped to accomplish his purpose were deplorably unsound. The treaty of 1834 involved interference in the domestic affairs of Spain, and that in combination with the very Power the ascendancy of which over the Spanish government it was his secret object to diminish.