But meanwhile clouds were beginning to appear on the horizon. In the United Presbyterian Synod there was a small minority of sturdy Voluntaries who, while not opposed to Union, were apprehensive that the price to be paid for it would be the partial surrender of their testimony in behalf of their distinctive principle. They did not wish to impose their beliefs on others, but they were anxious to reserve to themselves full liberty to hold and propagate their views in the United Church, and they were not sure that, by accepting the Articles of Agreement, they were in fact doing this. The efforts of Dr. Cairns and others were directed, not without success, to meeting their difficulties. But in the Free Church a more formidable opposition began to show itself. There had always been a conservative element in that Church, represented by men who held tenaciously to the more literal interpretation of its ecclesiastical documents and traditions; and, as the discussions went on, it became clear that the hopelessness of a reconciliation with the Establishment was not so universally felt as had been at first supposed. The supporters of the Union movement included almost all the trusted leaders of the Church—men like Drs. Candlish, Buchanan, Duff, Fairbairn, Rainy, and Guthrie, Sir Henry Moncreiff, Lord Dalhousie, and Mr. Murray Dunlop, most of whom had got their ecclesiastical training in the great controversy which had issued in the Disruption; but all their eloquence and all their skill did not avail to allay the misgivings or silence the objections of the other party. At length in 1867 a crisis was reached. The Articles of Agreement, after having been finally formulated by the Committee, had been sent down to Presbyteries for their consideration; and the reports of the Presbyteries were laid on the table of the Assembly of that year. The question now arose, Was it wise, in view of the opposition, to take further steps towards Union? The Assembly by 346 votes to 120 decided to goon; whereupon the Anti-Union leaders resigned the seats which up to this time they had retained on the Union Committee.
It is true that, after the Committee had been relieved of this hostile element, considerable and rapid progress was made. Hopes were cherished for a time that the Union might yet be consummated, and the determination was expressed to carry it through at all hazards. But the Free Church minority, ably led and knowing its own mind, stubbornly maintained its ground. Its adherents, who included perhaps one-third of the ministers and people of the Church, were specially numerous in the Highlands, where United Presbyterianism was practically unrepresented.