Occasion of Visit to the United States--First Impressions of the Mississippi--Magnitude of that River--Impediment at its Entrance--The New Harbour--The "Great" and "Fat" Valley--High-Pressure Steam-Tug Frolics--Slave-Auction Facetiae. The ill health of my wife, occasioned by long residence amid the sultry swamps of Guiana, compelled me a few months ago to accompany her on a visit to the United States of America. Having taken our passage in a ship to New Orleans, we found ourselves in fifteen days on the far-famed Mississippi,--the "father of waters." On gazing around, our first feeling was one of awe, to find ourselves actually ascending that majestic stream, that great artery of the greatest valley in the world, leading into the very heart of a continent. The weather was very cold; the trees on the river's bank were leafless; and the aspect of nature on every hand told it was winter. What a change! But a fortnight before we were panting under an almost vertical sun. We found the Mississippi much narrower than we had anticipated. In some places it is only about half a mile wide; while below New Orleans it never, I should say, exceeds a mile in width. This is remarkable, since not less than fifty-seven large navigable rivers contribute to swell its waters. It is, however, very deep, and, even at the distance of 500 miles above New Orleans, is navigated by vessels of 300 tons; nay, at 1,364 miles from its mouth, it attains an average depth of fifteen feet. In its course, it waters 2,500 miles of country. Among the rivers that pour themselves into this immense stream are--the Missouri, which has first traversed a space of 2,000 miles; the Arkansas, 1,300 miles; the Red River, 1,000 miles; and the Ohio, 700 miles.