Who has not heard of the Himalayas-those Titanic masses of mountains that interpose themselves between the hot plains of India and the cold table-lands of Thibet-a worthy barrier between the two greatest empires in the world, the Mogul and the Celestial? The veriest tyro in geography can tell you that they are the tallest mountains on the surface of the earth; that their summits-a half-dozen of them at least-surmount the sea-level by more than five miles of perpendicular height; that more than thirty of them rise above twenty thousand feet, and carry upon their tops the eternal snow