Picture to yourself a wild ravine, gashing a mountain spur, and with here and there in its course abrupt descents. One of these is so deep and sheer that it might be called a precipice. High above it, from the steep slope on either hand, beetling crags jut out. Their summits almost meet at one point, and thus the space below bears a rude resemblance to a huge window. Through it you might see the blue heights in the distance; or watch the clouds and sunshine shift over the sombre mountain across the narrow valley; or mark, after the day has faded, how the great Scorpio draws its shining curves along the dark sky.