The Potomac is one of the chief among the many rivers draining the Allegheny Mountains. It originates in two branches, rising in West Virginia and uniting northwest of Cumberland; is nearly four hundred miles long; has remarkably picturesque scenery in the magnificent gorges and reaches of its upper waters; breaks through range after range of the Alleghenies, and after reaching the lowlands becomes a tidal estuary for a hundred miles of its final course, broadening to six and eight and ultimately sixteen miles wide at its mouth in the Chesapeake. Washington is near the head of tidewater, one hundred and twenty-five miles from the bay; and for almost its entire course the Potomac is an interstate boundary, between Maryland and West Virginia and Virginia. Its name is Indian, referring to its use in their primitive navigation, the original word "Petomok" meaning "they are coming by water"--"they draw near in canoes." The Alleghenies, where this noted river originates, are a remarkable geological formation. The Atlantic Coast of the United States has a general trend from the northeast to the southwest, with bordering sand beaches, and back of them a broad band of pines. Then, towards the northwest, the land gradually rises, being formed in successive ridges, with intervening valleys, until it reaches the Alleghenies. The great ranges of this mountain chain, which is geologically known as the Appalachian System, run almost parallel to the coast for over a thousand miles, from the White Mountains of New Hampshire down to Alabama. They are noted mountains, not very high, but of remarkable construction, and are said to be much older in geological formation than the Alps or the Andes. They are composed of series of parallel ridges, one beyond the other, and all following the same general course, like the successive waves of the ocean. For long distances these ridges run in perfectly straight lines, and then, as one may curve around into a new direction, all the others curve with it. The intervening valleys are as remarkable in their parallelism as the ridges enclosing them. From the seaboard to the mountains the ranges of hills are of the same general character, but with less elevation, gentler slopes, and in most cases narrower and much more fertile valleys.