On the evening of Tuesday, June 14, 1864, immediately after the defeat of the ministry on an unimportant question, Brown spoke to two Conservative members and promised to co-operate with any government that would settle the constitutional difficulty. These members, Alexander Morris and John Henry Pope, were on friendly terms with him and became serviceable intermediaries. They were asked to communicate this promise to Macdonald and to Galt. The next day saw the reconciliation of the two leaders who had been estranged for ten years. They met 'standing in the centre of the Assembly Room' (the formal memorandum is meticulously exact in these and other particulars), that is, neither member crossing to that side of the House led by the other. Macdonald spoke first, mentioning the overtures made and asking if Brown had any 'objection' to meet Galt and himself. Brown replied, 'Certainly not.' Morris arranged an interview, and the following day Macdonald and Galt called upon Brown at the St Louis Hotel, Quebec. Negotiations, ending in the famous coalition, began.

The memorandum read to the House related in detail every step taken to bring about the coalition, from the opening conversation which Brown had with Morris and Pope. It was proper that a full explanation should be given to the public of a political event so extraordinary and so unexpected. But the narrative of minute particulars indicates the complete lack of confidence existing between the parties to the agreement. The relationships of social life rest upon the belief that there is a code of honour, affecting words and actions, which is binding upon gentlemen. The memorandum appeared to assume that in political life these considerations did not exist, and that unless the whole of the proceedings were set forth in chronological order, and with amplitude of detail, some of the group would seek to repudiate the explanation on one point or another, while the general public would disbelieve them all. To such a pass had the extremes of partyism brought the leading men in parliament. If, however, the memorandum is a very human document, it is also historically most interesting and important. The leaders began by solemnly assuring each other that nothing but 'the extreme urgency of the present crisis' could justify their meeting together for common political action. The idea that the paramount interests of the nation, threatened by possible invasion and by commercial disturbance, would be ground for such a junction of forces does not seem to have suggested itself. After the preliminary skirmishing upon matters of party concern the negotiators at last settled down to business.

Mr Brown asked what the Government proposed as a remedy for the injustice complained of by Upper Canada, and as a settlement of the sectional trouble. Mr Macdonald and Mr Galt replied that their remedy was a Federal Union of all the British North American Provinces; local matters being committed to local bodies, and matters common to all to a General Legislature.[[3]]

Mr Brown rejoined that this would not be acceptable to the people of Upper Canada as a remedy for existing evils. That he believed that federation of all the provinces ought to come, and would come about ere long, but it had not yet been thoroughly considered by the people; and even were this otherwise, there were so many parties to be consulted that its adoption was uncertain and remote.

Mr Brown was then asked what his remedy was, when he stated that the measure acceptable to Upper Canada would be Parliamentary Reform, based on population, without regard to a separating line between Upper and Lower Canada. To this both Mr Macdonald and Mr Galt stated that it was impossible for them to accede, or for any Government to carry such a measure, and that, unless a basis could be found on the federation principle suggested by the report of Mr Brown's committee, it did not appear to them likely that anything could be settled.

At this stage, then, Brown thought federation should be limited to Canada, believing the larger scheme uncertain and remote, while the others preferred a federal union for all the provinces. At a later meeting Cartier joined the gathering and a confidential statement was drawn up (the disinclination to take one another's word being still a lively sentiment), so that Brown could consult his friends. The ministerial promise in its final terms was as follows:

The Government are prepared to pledge themselves to bring in a measure next session for the purpose of removing existing difficulties by introducing the federal principle into Canada, coupled with such provisions as will permit the Maritime Provinces and the North-West Territory to be incorporated into the same system of government. And the Government will seek, by sending representatives to the Lower Provinces and to England, to secure the assent of those interests which are beyond the control of our own legislation to such a measure as may enable all British North America to be united under a General Legislature based upon the federal principle.

This basis gave satisfaction all round, and the proceedings relapsed into the purely political diplomacy which forms the least pleasant phase of what was otherwise a highly patriotic episode, creditable in its results to all concerned. Brown fought hard for a representation of four Liberals in the Cabinet, preferring to remain out of it himself, and, when his inclusion was deemed indispensable, offering to join as a minister without portfolio or salary. Finally Macdonald promised to confer with him upon the personnel of the Conservative element in the Cabinet, so that the incoming Liberals would meet colleagues with whom harmonious relations should be ensured. The fates ordained that, since Brown had been the first to propose the sacrifice of party to country, the arrangement arrived at was the least advantageous to his interests. He had the satisfaction of feeling that the Upper Canada Liberals in the House supported his action, but those from Lower Canada, both English and French, were entirely unsympathetic. The Lower Canada section of the ministry accordingly remained wholly Conservative.