The next letter from the Major-General, dated from York, the 28th July, principally relates to the approaching meeting of the legislature, and mentions his intention of detaching a force for the relief of Amherstburg. A letter from the same place, written on the following day, communicates the surrender of Michilimachinac, and particularly acknowledges the receipt of Sir George Prevost's despatches of the 7th and 10th July, written _after the declaration of war_, and before alluded to. General Brock also states his intention of embarking immediately in the Prince Regent, (the vessel which had been built and equipped since the month of March preceding), for Fort George, from whence he should speedily return to York. On the 4th August, a short letter was addressed by General Brock to Sir G. Prevost, from York, principally upon the proceeding of the legislature, regarding the militia laws, and on the following day he set off for Amherstburg, from whence he did not return until after the glorious termination of Hull's invasion. It was, therefore, from a consideration of the nature of his resources, and of the necessity of maturing and husbanding them, and from a conviction that Niagara would easily fall whenever he should be inclined to attack it, and not from any doubt arising from want of instructions, that General Brock abandoned the attempt. It was in further pursuance of the line of policy adopted at the commencement of the war, that Sir George Prevost, upon the receipt of despatches from Mr. Foster, acquainting him with the proposed repeal of the Orders in Council by the British Government, immediately opened a communication with Major-General Dearborn, commanding the American forces on the frontier of Lower Canada, for the purpose of concluding an armistice, until the Congress should determine upon the proposals transmitted to them by Mr. Foster. An armistice of about three weeks did accordingly take place; and whatever might be the advantage arising from it to the American commanders and their troops, from the time and opportunity it afforded them of increasing their means of attacking the Canadas, it is obvious that the cessation of hostilities was of far more importance to Sir George Prevost, by enabling him to mature his preparations for defence. In fact, at the very time the armistice was negotiating, a regiment had arrived in the river from the West Indies; and after the conclusion, and during the continuance of it, considerable reinforcements of men and supplies were forwarded to Upper Canada, where they armed before the resuming of hostilities, and materially contributed towards defeating the attempts which the enemy afterwards made to invade that province.