Read it through once

We had agreed to descend the Rhine in a boat from Strasburgh to Rotterdam, whence we might take shipping for London. During this voyage we passed many willowy islands and saw several beautiful towns. We stayed a day at Mannheim, and on the fifth from our departure from Strasburgh, arrived at Mainz. The course of the Rhine below Mainz becomes much more picturesque. The river descends rapidly and winds between hills, not high, but steep, and of beautiful forms. We saw many ruined castles standing on the edges of precipices, surrounded by black woods, high and inaccessible. This part of the Rhine, indeed, presents a singularly variegated landscape. In one spot you view rugged hills, ruined castles overlooking tremendous precipices, with the dark Rhine rushing beneath; and on the sudden turn of a promontory, flourishing vineyards with green sloping banks and a meandering river and populous towns occupy the scene.