The rivers which rise on the eastern side of the Appalachian range run into the Atlantic; those which rise west of the Rocky Mountains empty themselves into the Pacific; while the mighty streams which flow between the two, pass through the great basin of the Mississippi, and swell the waters of that mother of rivers. The great valley of the Mississippi, indeed, drains a surface greater than that of any other river on the globe, with the exception perhaps of the Amazon. The Missouri, even before it reaches it, runs a course of 1300 miles, while the Mississippi itself, before its confluence with the Missouri, has already passed over a distance of 1200 miles; thence to its mouth its course is upwards of 1200 miles more. The Arkansas, which flows into it, is 2000 miles long, and the Red River of the south 1500 miles in length; while the Ohio, to its junction with the Mississippi, is nearly 1000 miles long. North America may be said to contain four great valleys--that of the Mississippi, running north and south; that of the Saint Lawrence, from the south-west to the north-east; that of the Saskatchewan, extending from the Rocky Mountains below Mount Brown to Lake Superior; that of the Mackenzie, from the Great Slave Lake to the Arctic Ocean. Although a large portion of the eastern side of the continent is densely-wooded, there are towards the west, extending from the Gulf of Mexico to the Arctic Ocean, vast plains. In the south they are treeless and barren in the extreme; while advancing northward they are covered with rich grasses, which afford support to vast herds of buffaloes, as well as deer and other animals. LAKES. The most remarkable feature in North America is its lake system--the largest and most important in the world. In the north-west, at the foot of the Rocky Mountains, are the Great Bear and Great Slave Lakes, which discharge their waters through the Mackenzie River into the Arctic Ocean. Next we have the Athabasca, Wollaston, and Deer Lakes. In the very centre of the continent are the two important lakes of Winnipeg and Winnipegoos,--the former 240 miles in length by 55 in width, and the latter about half the size. The large river of the Saskatchewan flows into Lake Winnipeg, and with it will, ere long, form an important means of communication between the different parts of that vast district lately opened up for colonisation. At its southern end the Red River of the north flows into it, on the banks of which a British settlement has long been established. Several streams, however, make their way into Hudson Bay. Between it and Lake Superior is an elevated ridge of about 1500 feet in height; the streams on the west falling into Lake Winnipeg, while those which flow towards the east reach Lake Superior.