The enlargement of the Ottawa and Rideau canals is of obvious importance, and outlying works might be traced which could be used in case of invasion to hold the enemy in check; but still, as a precautionary measure, it would be desirable to remove the more important stores at Montreal to Quebec and Ottawa, if it is in contemplation to make this valuable position subsidiary to any other place in Canada. Permanent works might be erected at St. John’s, the Isle aux Noix and St. Helen’s Island, where forts should be reconstructed on improved principles. But the most obvious measure, in the opinion of some engineers, the fortification of the hill over the city, and the erection of a Citadel upon it, which would render the mere occupation of the town below valueless to an enemy, is not approved of by more recent authorities. Gunboats on Lake St. Louis would prove most valuable in defending the works at Vaudrueuil. Quebec is however the key of Canada; and that key can be wrested from our own grasp at any moment by a determined enemy, unless the recommendations so strongly urged from time to time by all military authorities meet with consideration. The old enceinte should be removed, and the French works restored, according to the suggestions of scientific officers, and of the ablest engineers we possess. An entrenched camp might be marked out to the west of the Citadel, with a line of parapet and redoubts extending from the St. Lawrence to the St. Charles river. In order to cover the city from an attack on the south side, it would be necessary to occupy Point Levi, and to construct a strong entrenched line, with redoubts at such a distance as would prevent the enemy from coming near the river to shell the city and citadel. But it is evident that they are _nil ad rem_, unless behind these works, and in support of them in the open, can be assembled a force of sufficient strength to prevent an investment, or to attack the investing armies, and at the same time to hold front against them in the field. It is estimated that 150,000 men might hold the whole of the Canadas, East and West, against twice that number of the enemy. If we are to judge by what has passed, it is not probable the United States will be inclined or able for such an effort. Quebec might be held with 10,000 men against all comers. From 25,000 to 30,000 men would make Montreal safe. Kingston would require 20,000 men, and Ottawa would need 5000. The greater part, if not all of them, might be composed of militia, and volunteers trained to gunnery and the use of small arms. For the protection of the open country, and to meet the enemy in the field, an army of from 25,000 to 35,000 men would be needed from Lake Ontario to Quebec. The western district on Lake Erie could not be protected by less than 60,000 men.