The principal arguments in favor of the United States building the inter-oceanic canal were its utility as a measure of preparedness for and strategy in case of war. By furnishing quick passage between the east and west coasts the navy necessary for the protection of these coasts could be reduced one half. With the canal entirely in the control of the Government no foreign nation could take advantage of it to our detriment. Notwithstanding the need of the canal for war purposes, the benefits to be derived by the commerce of peace will doubtless be manifold more valuable. It furnishes cheap transportation between the west and east coasts, and shortens materially the distance from the Atlantic seaboard to western South America as well as to the islands of the Pacific Ocean. During the year 1920, “2814 ships representing 11,236,119 tons of cargo, passed through the waterway” being a considerable increase over any preceding year.[67] Of these 45.5 per cent were registered United States vessels, more than any other one nation. Fuel-oil, nitrates, steel and iron hold leading places in the line of commodities carried. =River Transportation.=--As has already been stated streams and rivers were early adopted as a means for transportation. Birch-bark and dug-out canoes, flat-boats and keel-boats, with and without sails, and rafts were extensively used. For small boats paddles and oars furnished the means of navigation, while several pairs of oars were utilized on the larger boats. In shallow water poling was much in vogue. Two men by pushing poles against the bottom of the stream from opposite sides of a small boat could easily propel it. On still larger boats and rafts the men as they pushed walked toward the stern as far as possible while the craft moved through the water under them. A third man held it with his pole until the first two regained a position near the front for another push. By this arduous and crude means boats were propelled up shallow but often swift currents. On the larger rivers sails were employed. Going downstream offered little difficulty except to keep clear of sand bars and snags. Sails, oars, and poles were sometimes relied upon to assist the current in making speed. Large rafts of logs and lumber made by tying timbers together with wooden pins were floated down the rivers and broken up and sold when they reached their destination. Furs, hides, bacon, cured hams, or jerked-meat might form a cargo, stored during transit, in a small cabin erected at the center of the raft, which might occupy from 400 to 600 square feet.