It is a very important point, in considering this question of the enlargement of existing canals and the construction of new ones, that they have, under the new conditions of naval warfare, come to be an important element in the harbor defences of the Lakes. We have the testimony of Captain Ericsson himself, whose Monitor vessels have already done so much for the country, as to this availability. He writes,--"An impregnable war-vessel, twenty-five feet wide and two hundred feet long, with a shot-proof turret, carrying a gun of fifteen inch calibre, with a ball of four hundred and fifty pounds, and capable of destroying any hostile vessel that can be put on the Lakes, will draw, without ammunition, coal, or stores, but six feet and six inches water, and consequently will need only a canal wide and deep enough to float a vessel of those dimensions, with locks of sufficient size to pass it." Great Britain has already secured to herself the means of access to the Lakes by her system of Canadian canals, and the Military Committee of the House express the opinion, that, in case of a war with that power, "a small fleet of light-draught, heavily armed, iron-clad gunboats, could, in one short month, in despite of any opposition that could be made by extemporized batteries, pass up the St. Lawrence, and shell every city and village from Ogdensburg to Chicago. At one blow it could sweep our commerce from that entire chain of lakes. Such a fleet would have it in its power to inflict a loss to be reckoned only by hundreds of millions, so vast is the wealth thus exposed to the depredations of a maritime enemy." We were saved from such a blow, a few months ago, only by the failure of the Rebel agents in Canada to procure, either by purchase or piracy, a swift armed steamer. Ever since the War of 1812, England has been preparing, in the event of another war, to strike at this, our vital point. In 1814 the Duke of Wellington declared "that a naval superiority on the Lakes is a _sine qua non_ of success in war on the frontier of Canada." Years before, William Hall, Governor of the Northwestern Territory, made the same declaration to our Government, and the capture of Detroit by the British in 1812 was due to their failure to respond to his appeal for a naval force. In 1817 the Lakes were put on a peace establishment of one gun on each side, which was a good bargain for England, she having at that time larger interests on the Lakes than the United States. Now ours exceed hers in the ratio of four to one.